stratospheric ozone climatology and variability over a southern

14
Ann. Geophys., 25, 2321–2334, 2007 www.ann-geophys.net/25/2321/2007/ © European Geosciences Union 2007 Annales Geophysicae Stratospheric ozone climatology and variability over a southern subtropical site: Reunion Island (21 S; 55 E) V. Sivakumar 1,* , T. Portafaix 1 , H. Bencherif 1 , S. Godin-Beekmann 2 , and S. Baldy 1 1 Laboratoire de l’Atmosph` ere et des Cyclones, UMR CNRS 8105, Universit´ e de La R´ eunion, Reunion Island, France 2 Service d’A´ eronomie, UMR CNRS 7620, Paris, France * now at: National Laser Centre, Council for Scientific and Industrial Research (CSIR), P.O. Box: 395, Pretoria, South Africa Received: 27 March 2007 – Revised: 2 October 2007 – Accepted: 5 November 2007 – Published: 29 November 2007 Abstract. The study presents the climatological character- istics of stratospheric ozone observed over Reunion Island using in-situ (ozonesonde and SAOZ) and satellite (UARS- HALOE, SAGE-II and TOMS) measurements. It uses co- localised ozonesondes (from September 1992 to February 2005) and SAOZ measurements (from January 1993 to De- cember 2004), SAGE-II data from October 1984 to February 1999 (15 years), HALOE data from January 1991 to Febru- ary 2005 (15 years), and NIMBUS/TOMS data from Jan- uary 1978 to December 2004 (27 years). The satellite mea- surements correspond to overpasses located nearby Reunion Island (21 S; 55 E). The height profiles of ozone concen- tration obtained from ozonesonde (0.5–29.5 km) show less bias in comparison with the HALOE and SAGE-II measure- ments. Though, the satellite (HALOE and SAGE-II) mea- surements underestimate the tropospheric ozone, they are in good agreement for the heights above 15 km. The bias be- tween the measurements and the normalized ozone profile constructed from the ozonesonde and SAGE-II satellite mea- surement shows that the SAGE-II measurements are more accurate than the HALOE measurements in the lower strato- sphere. The monthly variation of ozone concentration de- rived from ozonesonde and HALOE shows a nearly annual cycle with a maximum concentration during winter/spring and minimum concentration during summer/autumn months. The time evolution of total column ozone obtained from TOMS, SAOZ and the one computed from ozonesonde and SAGE-II, exhibits similar behaviour with analogous trends as above. The TOMS variation displays a higher value of total column ozone of about 3–5 DU (10%) in comparison with the SAOZ and the integrated ozone from ozonesonde and SAGE-II. Correspondence to: V. Sivakumar ([email protected]) Keywords. Atmosphere composition and structure (Mid- dle atmosphere – composition and chemistry) – Meteorol- ogy and atmospheric dynamics (Climatology; Middle at- mosphere dynamics; Tropical meteorology; Instruments and techniques) 1 Introduction Ozone plays an important role in the earth’s radiation bud- get by preventing UV radiation from penetrating the earth’s atmosphere. The stratosphere is a region in the earth atmo- sphere which exhibits maximum ozone concentration and helps to prevent UV radiation from penetrating the atmo- sphere and the earth surface (see review article by Staehe- lin et al., 2001). On the other-hand, the troposphere ozone concentration acts as an atmospheric pollutant and leads to global warming. Therefore, understanding ozone concentra- tion variations in the stratosphere and troposphere height re- gions is of great importance to the research community. There are different remote sensing instruments to provide vertical ozone profiles, such as spectrometers, ozonesondes, lidars, etc. Ozonesondes are recognized to be an effective tool for measuring ozone in the troposphere and part of the stratosphere (Beekman et al., 1994; Logan, 1999). Logan (1999) investigated the ozone variation in the lower strato- sphere using ozonesonde data from the northern hemisphere and observed that the amount of ozone decreases between the tropopause and 100 hPa from March to September due to an increase in the tropopause height. Fujiwara et al. (2000) provided the seasonal variations of troposphere ozone over Indonesia (Watukosesk, 7.5 S; 112.6 E) using 5 years of ozonesonde measurements. The seasonal variations showed an enhanced ozone-mixing ratio during dry season (August- November), in comparison with the other seasons which is Published by Copernicus Publications on behalf of the European Geosciences Union.

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Page 1: Stratospheric ozone climatology and variability over a southern

Ann Geophys 25 2321ndash2334 2007wwwann-geophysnet2523212007copy European Geosciences Union 2007

AnnalesGeophysicae

Stratospheric ozone climatology and variability over a southernsubtropical site Reunion Island (21 S 55 E)

V Sivakumar1 T Portafaix1 H Bencherif1 S Godin-Beekmann2 and S Baldy1

1Laboratoire de lrsquoAtmosphere et des Cyclones UMR CNRS 8105 Universite de La Reunion Reunion Island France2Service drsquoAeronomie UMR CNRS 7620 Paris France now at National Laser Centre Council for Scientific and Industrial Research (CSIR) PO Box 395 Pretoria South Africa

Received 27 March 2007 ndash Revised 2 October 2007 ndash Accepted 5 November 2007 ndash Published 29 November 2007

Abstract The study presents the climatological character-istics of stratospheric ozone observed over Reunion Islandusing in-situ (ozonesonde and SAOZ) and satellite (UARS-HALOE SAGE-II and TOMS) measurements It uses co-localised ozonesondes (from September 1992 to February2005) and SAOZ measurements (from January 1993 to De-cember 2004) SAGE-II data from October 1984 to February1999 (sim15 years) HALOE data from January 1991 to Febru-ary 2005 (sim15 years) and NIMBUSTOMS data from Jan-uary 1978 to December 2004 (27 years) The satellite mea-surements correspond to overpasses located nearby ReunionIsland (21 S 55 E) The height profiles of ozone concen-tration obtained from ozonesonde (05ndash295 km) show lessbias in comparison with the HALOE and SAGE-II measure-ments Though the satellite (HALOE and SAGE-II) mea-surements underestimate the tropospheric ozone they are ingood agreement for the heights above 15 km The bias be-tween the measurements and the normalized ozone profileconstructed from the ozonesonde and SAGE-II satellite mea-surement shows that the SAGE-II measurements are moreaccurate than the HALOE measurements in the lower strato-sphere The monthly variation of ozone concentration de-rived from ozonesonde and HALOE shows a nearly annualcycle with a maximum concentration during winterspringand minimum concentration during summerautumn monthsThe time evolution of total column ozone obtained fromTOMS SAOZ and the one computed from ozonesonde andSAGE-II exhibits similar behaviour with analogous trendsas above The TOMS variation displays a higher value oftotal column ozone of about 3ndash5 DU (10) in comparisonwith the SAOZ and the integrated ozone from ozonesondeand SAGE-II

Correspondence toV Sivakumar(svenkataramancsircoza)

Keywords Atmosphere composition and structure (Mid-dle atmosphere ndash composition and chemistry) ndash Meteorol-ogy and atmospheric dynamics (Climatology Middle at-mosphere dynamics Tropical meteorology Instruments andtechniques)

1 Introduction

Ozone plays an important role in the earthrsquos radiation bud-get by preventing UV radiation from penetrating the earthrsquosatmosphere The stratosphere is a region in the earth atmo-sphere which exhibits maximum ozone concentration andhelps to prevent UV radiation from penetrating the atmo-sphere and the earth surface (see review article by Staehe-lin et al 2001) On the other-hand the troposphere ozoneconcentration acts as an atmospheric pollutant and leads toglobal warming Therefore understanding ozone concentra-tion variations in the stratosphere and troposphere height re-gions is of great importance to the research community

There are different remote sensing instruments to providevertical ozone profiles such as spectrometers ozonesondeslidars etc Ozonesondes are recognized to be an effectivetool for measuring ozone in the troposphere and part of thestratosphere (Beekman et al 1994 Logan 1999) Logan(1999) investigated the ozone variation in the lower strato-sphere using ozonesonde data from the northern hemisphereand observed that the amount of ozone decreases betweenthe tropopause and 100 hPa from March to September due toan increase in the tropopause height Fujiwara et al (2000)provided the seasonal variations of troposphere ozone overIndonesia (Watukosesk 75 S 1126 E) using 5 years ofozonesonde measurements The seasonal variations showedan enhanced ozone-mixing ratio during dry season (August-November) in comparison with the other seasons which is

Published by Copernicus Publications on behalf of the European Geosciences Union

2322 V Sivakumar et al Ozone climatology and variability

most likely caused by biomass burning Their results arein accordance with the observations made over the equato-rial eastern pacific Cristobal Galapagos (09 S 896 W)by Shiotani et al (2002) A review by Staehelin et al (2001)addressed that the satellite and ground-based measurementsshow no significant ozone trends in the tropics but signifi-cant long-term negative trends of 2-4 in the northern andsouthern mid-latitudes Brinksma et al (2002) observed an-nual trends in troposphere-stratosphere ozone variation us-ing five years of ozone measurements from lidar ozonesondeand satellite data over a mid-latitude station Lauder (45 S170 E) They have observed high concentrations during win-ter Using Southern Hemisphere ADditional OZonesonde(SHADOZ) Thompson et al (2003b) presented the tropo-sphere ozone climatology using 3 years of ozonesonde obser-vations for different stations over southern hemisphere Theobservations are concentrated especially over tropicssub-tropical station and noticed a maximum ozone concentrationduring the winterspring period

Although the ozonesonde measurements are precise forthe troposphere and lower stratosphere height regions theyare unable to provide a global picture (Barnes et al 1985Tiao et al 1986) On the other hand satellite measure-ments provide a global coverage with very low frequencyof observation requirements for a particular site The Halo-gen Occultation Experiment (HALOE) on UARS and Strato-spheric Aerosol and Gas Experiment (SAGE) provide a rel-atively better estimation of ozone with good vertical res-olution even at tropospheric altitudes though less in fre-quency of observations for a given site Lu et al (1997) com-pared HALOE SAGE-II and ozonesonde data from Northernhemisphere (Payerne 468 N 695 E) and Southern hemi-sphere (Lauder 450 S 16968 E and Macquarie Island545 S 15895 E) Their studies suggested that HALOESAGE-II and ozonesonde measurements are in good agree-ment especially above 20 km Bhatt et al (1999) concludedthat HALOE is providing accurate ozone profile in the lowerstratosphere whilst the correction for aerosols interferenceis well characterized and when there is no cirrus layers de-tected Newchurch et al (2000) using SAGE-III data forlonger period of about 20 years (1978ndash1998) noted thatthe maximum decline in ozone trends occurred atsim40 kmThe studies further evidenced a large negative trends presentfor the extra-tropics (minus10year) compared to the tropics(minus06year) Dorokhov et al (2002) stated that the compar-ison between satellite and ground-based measurements per-mits a better understanding of the characteristics and weak-ness of each data set

Besides height profiles of ozone the total columns ofozone have been studied by various researchers Chandraet al (1996) presented the mid-latitude total ozone trends inthe northern hemisphere and noticed that they are influencedby inter annual variability which is associated with dynam-ical perturbations in the atmosphere during the winter andspring months They also estimated that due to both radia-

tive and dynamical processes a strong positive correlationbetween total ozone and lower stratospheric temperaturesexists Ziemke and Chandra (1999) discussed the signifi-cance of biomass burning in generating seasonal and zonalanomalies in total ozone over tropics using 20 years of to-tal ozone mapping spectrometer (TOMS) data Their studyillustrated an annual cycle with a maximum ozone concentra-tion during September and October from 15 N to 15 S Thebiomass burning was found to occur at different times fornorthern and southern hemispheres However recent stud-ies based on three-dimensional atmospheric chemistry andtransport models suggest that photochemical ozone forma-tion due to biomass may be less important (Lelieveld andDentener 2000 Marufu et al 2000 Moxim and Levy 2000Chandra et al 2002)

It is apparent from all the above recent studies that thereis considerable interest within scientific community to studythe substantial decreaseincrease in stratospheretroposphereozone Over tropical and sub-tropical regions the ozonemeasurements are very few especially in the southern hemi-sphere (WMO 1999 Staehelin et al 2001) though it hasa significant contribution in the global climate change Re-union Island (21 S 55 E) is located over southern sub-tropics and is influenced by a number of atmospheric per-turbations such as cyclone Inter Tropical Convective Zone(ITCZ) passages strong jet streams etc where the study onozone variations play an important role in addressing dif-ferent aspects of the climate In this study we report onthe climatological characteristics of stratospheric ozone overReunion Island (21 S 55 E) using in-situ ozonesonde data(13 years) and its comparison with UARS-HALOE data (15years) The study also attempted to validate the SAOZ mea-surements taken over Reunion Island by comparing with totalozone measurements from TOMS and those obtained by inte-grating ozonesonde and SAGE-II data (hereafter OAS) Thepaper is organized as follows Sect 2 provides a brief sketchon data used Sect 3 presents the climatological results ob-tained from ozonesonde and HALOE comparison betweenthe ozone measurements from ozonesonde and HALOEtemporal evolution of ozone and anomalies between the mea-surements and comparison of total column ozone measure-ments from TOMS and SAOZ Sect 4 summarizes and con-cludes the results In addition an appendix is included andit provides the monthly mean climatological value of ozoneconcentration and standard deviation over Reunion Island forthe height region from ground to 30 km

2 Data

21 Ozonesonde data

The radiosonde accompanied with Electrochemical Concen-tration Cell (ECC) is used for measuring height profiles ofozone from sea level to about 30 km The radiosondes were

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2323

launched twice a month from September 1992 to December1999 and once a week from January 1999 to at-present Therecorded ozone measurements are converted to concentra-tions (molcm3) and used for the present study The datahas also been collected regularly on both SHADOZ and Net-work for Detection of Atmospheric Composition and Change(NDACC) programmes More details about the data andquality of ozonesonde measurements are found in the liter-ature (Fujiwara et al 2000 Thompson et al 2003a b) andalso specifically for the Reunion ozonesonde measurements(Baldy et al 1996 Randriambelo et al 2000 and Sivakumaret al 2006)

We use 13 years of ozonesonde data gathered fromSeptember 1992 to February 2005 and the height region fromground to 30 km The monthly distributions of data are pre-sented in the Fig 1 (grey colored bars)

22 HALOE-UARS satellite data

HALogen Occultation Experiment (HALOE) was launchedon the Upper Atmosphere Research Satellite (UARS) space-craft on 12 September 1991 as a part of the Earth ScienceEnterprise (ESE) program The experiment uses solar occul-tation to measure the vertical profile of minor constituents(O3 H2O NO2 HCl HF NO and CH4) aerosol concentra-tions and temperature with a height resolution of 37 km foran instantaneous field of view of 16 km at the earth limbIt uses the atmospheric transmission measurements in the28microm CO2 band for the retrieval of ozone mixing ratioThe retrieval method applies a simple ldquoonion-peelrdquo proce-dure to stabilize the height profile at top and bottom The ob-tained ozone profiles are accurate for the height range from10 km to 90 km with a possible error of 5 to 10 More de-tails about HALOE data analysis and quality are discussedin the following literature (eg Russell et al 1993 Ran-del et al 1995 Bruhl et al 1996 Cunnold et al 1996Natarajan and Callis 1997 Grooss et al 1999 and Roodet al 2000 Remsberg et al 2001) and can be cited athttphaloedatalarcnasagovhomeindexphpsite

The present study uses 15 years (September 1991 toFebruary 2005) of data (version 19) acquired during the pas-sage of HALOE satellite over Reunion (21 S 55 E) withlatitudinal and longitudinal discrepancies ofplusmn5 andplusmn25 The monthly distributions of data are sketched in the Fig 1(shaded bars)

23 SAGE-II satellite data

Stratospheric Aerosol and Gas Experiment II (SAGE-II) wasinitiated into the Earth Radiation Budget Satellite (ERBS)in October 1984 The instrument uses the solar occultationtechnique to measure attenuated solar radiation of the Earthrsquoslimb The transmittance measurements are inverted using theldquoonion-peelrdquo approach to yield 1-km vertical resolution pro-files of aerosol extinction ozone nitrogen dioxide and water

Sivakumar et al Stratosphere ozone climatology over Reunion Page 25 of 34

FIGURE-1

Histogram represents the monthly distribution of Ozonesonde HALOE and SAGE-II

satellite data used for the present study and for the period from 1992 to 2005

Fig 1 Histogram represents the monthly distribution ofozonesonde HALOE and SAGE-II satellite data used for thepresent study and for the period from 1992 to 2005

vapour Extensive validation efforts were made to verify theaccuracy of these measurements and the data sets are nowarchived and available for general scientific use More de-tails on SAGE-II data could be found in Attmannspacher etal (1989) and Cunnold et al (1989)

SAGE-II ozone measurements for the height range from05 km to 705 km and for the period from October 1984to February 1999 (sim15 years) is used here The overallconstructed monthly mean profiles are used to merge withdaily ozonesonde measurement so that the ozone profilesextend from 05 km to 705 km and also to allow for thecomputation of the corresponding total columns of ozoneThe monthly distributions of data are presented in the Fig 1(blank bars)

24 TOMS satellite data

Total Ozone Mapping Spectrometer (TOMS) measures thetotal ozone content of the Earthrsquos atmosphere The instru-ment was first launched on the Nimbus 7 Spacecraft in 1978followed by Meteor and Earth Probe The nominal uncertain-ties of TOMS ozone data vary from 1 to 3 Further detailson the TOMS data are available athttptomsgsfcnasagovadeosadeoshtmland McPeters et al (1993)

We use data corresponding to Reunion site (21 S 55 E)obtained from TOMS for the period from July 1996 to De-cember 2004 and the earlier data obtained from NIMBUS-7from January 1978 to June 1996 The data is used to normal-ize the ozone profiles by integrating the ozone measurementsfrom ozonesonde and SAGE-II data (OAS) and also to makea comparison with SAOZ and the total ozone obtained fromOAS

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2324 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 26 of 34

FIGURE-2

Flow diagram represents the procedure followed to obtain the normalized ozone profile

OAS refers to the combined ozonesonde and SAGE-II profile

Daily ozonesonde data for the height range

from 05 km to 30 km

Daily TOMS data over Reunion

Monthly mean

Daily SAGE-II ozone data for the height range from 05 km to 705 km

Monthly mean Step down the height resolution into 1 km

Merging with SAGE-II gives OAS profile

Calculating the integrated ozone

Ratio between the TOMS and OAS total

ozone= Normalization factor

(NF)

Reconstructing the ozone profile by

multiplying the OAS profile by NF

= Normalized ozone profile

Fig 2 Flow diagram represents the procedure followed to ob-tain the normalized ozon profile OAS refers to the combinedozonesonde and SAGE-II profile

25 SAOZ data

The Systeme drsquoAnalyse par Observation Zenithale (SAOZ)instrument is a broad-band (290ndash640 nm) spectrometer andhas undergone various developments since 1988 (Pom-mereau and Piquard 1994) The earlier documents on inter-comparison with different instruments evidenced that thespread in ozone line-of-sight amount is better than 1 (Pom-mereau and Piquard 1994 Hoffman et al 1995 Vaughan etal 1997 Roscoe et al 1999) The vertical columns of ozoneare obtained from the line-of-sight columns and air-mass fac-tor (AMF) using the following relationship

O3(vert)=

(O3(slant) + O3(ref)

)AMF

(1)

Where O3(ref) is the reference ozone spectrum obtainedfrom the spectrometer on a clear day at low solar zenith an-gle Line-of-sight ozone is identified as slant ozone columnO3(slant) and is derived from a spectral band of 100 nm widecentered at 510 nm Real-time and re-analysis SAOZ pro-grams use the standard AMF which is calculated from radia-tive transfer model The value of AMF is found to vary withlatitude and is typically about 12 (ref Sarkissian 1992)

Here the total columns of ozone obtained by SAOZ fromJanuary 1993 to December 2004 are used for comparisonwith both TOMS and the integrated ozone from OAS

3 Results

31 Normalized ozone profile

A height profile of ozone is constructed for the height re-gion from 05 km to 705 km by combining ozonesonde andSAGE-II measurements which are normalized with total col-umn ozone from TOMS data Such profile has been used asa reference for comparing with the other measurements Theroutine adopted to derive the normalized profile is as follows

ndash Daily ozonesonde data is stepped down into 1 km heightresolution

ndash Using 15 years (October 1984 to February 1999) ofSAGE-II data the monthly mean ozone profiles are ob-tained for the height region from 05 km to 705 km

ndash Similarly the monthly mean total ozone values for Re-union Island are derived from 27 years of TOMS mea-surements (from January 1978 to February 2005)

ndash The ozonesonde and SAGE-II monthly mean pro-files (OAS) are merged appropriately for each pro-file at 3 km down to maximum height extended bythe ozonesonde taking into account the measurementerror at the higher heights The SAGE-II monthlymean profiles are correspondingly selected based onthe ozonesonde observational date The merging region(3 km) uses the mean ozone concentrations from SAGE-II and ozonesonde

ndash The above constructed OAS profiles are individuallyintegrated in order to retrieve the corresponding totalozone in terms of Dobson units The normalization fac-tor is defined as the ratio of the OAS total ozone to thecorresponding monthly mean TOMS values

ndash Thus the normalized ozone profile for the height regionfrom 05 km to 705 km is derived by multiplying theOAS profile by normalization factor

The above explained steps are demonstrated in a simplifiedflow chart (see Fig 2) It is also noted here that the cal-culated normalization factor for the complete datasets fromozonesonde SAGE-II and TOMS data is found to vary from102 to 109 with an overall standard deviations ofsim002

32 Height profile of mean ozone

Height profiles of mean ozone concentrations obtained fromozonesonde HALOE and SAGE-II measurements are pre-sented in Fig 3 This figure illustrates the accuracy ofozone measurements obtained from ozonesonde (in-situ)HALOE and SAGE-II satellite data It also validates theozone measurements and illustrates the respective instrumen-tal error and relative measurement differences Here theozonesonde measurements corresponds to the height region

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2325

from 05 km to 295 km and the HALOE and SAGE-II satel-lite data range from 05 km to 705 km Since the height res-olution of the SAGE-II measurements is 1 km the HALOEand ozonesonde data has also been stepped down to 1 km res-olution for uniformity Utilizing the above data the overallmean ozone profiles are constructed individually for eachinstrument irrespective of the year and month

Figure 3a displays the height profiles of ozone concen-trations obtained from ozonesonde SAGE-II and HALOEThe figure is superimposed with the height profile of nor-malized ozone concentrations which were obtained by theabove illustrated method Few differences in values are no-ticed due to different instruments and techniques The nor-malized ozone profiles illustrate a very close agreement be-tween the ozonesonde and SAGE-II satellite data indicatingthat the measurements are consistent The normalized ozoneprofile is in accordance to the ozonesonde measurements inthe lower troposphere and with SAGE-II and HALOE pro-files in the stratosphere up to about 40 km Above 40 kmthe SAGE-II and HALOE measurements indicate very lit-tle discrepancy in the ozone measurements The maximumozone concentrationsim45times1012 molcm3 is displayed by allthe instruments atsim26 km It also shows a small differencein the estimated ozone concentration by instrument SAGE-II and HALOE show similar values and aresim3 higher thanthe ozonesonde It is also clear from the Fig 3a that SAGE-II and HALOE are underestimating the ozone values in thelower tropospheric height region (below 10 km) as expectedfrom the satellite instruments which measure from top to bot-tom and the error increases downward in the troposphere (seealso Fig 3b) Relatively the SAGE-II measurements pro-vide a reasonable comparison with ozonesonde above 12 kmwhen compared to the HALOE which are in agreement above18 km

The relative percentage of deviation (bias) in the ozonemeasurements by ozonesonde HALOE and SAGE-II withrespect to the normalized ozone profile is calculated usingthe following expression

O3(bias) =

(O3(nor) minus O3(xxx)

)O3(nor)

lowast 1000 (2)

Where ldquoO3(xxx)rdquo refers to the ozone measurements fromozonesonde HALOE or SAGE-II

The calculated bias in ozone measurements is presentedin Fig 3b In other words it displays the relative differ-encesuncertainty in the ozone measurements The figuresubstantiates the underestimation of ozone measurements inthe lower troposphere by HALOE and SAGE-II It showsthat the ozone measurements in the troposphere obtainedfrom ozonesonde are having a lower bias than those obtainedfrom HALOE and SAGE-II Just below the ozone maximumheight SAGE-II shows the highest bias while ozonesondereveals the lowest one

The ozonesonde measurements illustrate that the bias iswithin 4ndash6 in the lower troposphere height region and a

Sivakumar et al Stratosphere ozone climatology over Reunion Page 27 of 34

FIGURE ndash 3

(a) Height profile of overall mean ozone concentration obtained from Ozonesonde SAGE-II

and HALOE The figure is superimposed with a normalized ozone concentration

obtained from Ozonesonde and SAGE-II

(b) Height profile of relative percentage of bias in the ozone concentrations measured by

Ozonesonde SAGE-II and HALOE with respect to the normalized ozone profile The

percentage of bias is the ratio between the difference in ozone values and the normalized

ozone profile

Fig 3 (a)Height profile of overall mean ozone concentration ob-tained from ozonesonde SAGE-II and HALOE The figure is su-perimposed with a normalized ozone concentration obtained fromozonesonde and SAGE-II(b) Height profile of relative percent-age of bias in the ozone concentrations measured by ozonesondeSAGE-II and HALOE with respect to the normalized ozone profileThe percentage of bias is the ratio between the difference in ozonevalues and the normalized ozone profile

higher bias of about 10ndash12 is noticed in the upper tro-posphere and lower stratosphere height region (18ndash32 km)Such differences are also remarkably less in comparison withday to day variations (standard deviation) Whereas boththe satellite (HALOE and SAGE-II) measurements demon-strate almost the same magnitude of relative difference andis more than 40 in the lower troposphere However the biasis lower and of almost the same magnitude in the stratosphereheight region (sim above 20 km) The satellite and ozonesondemeasurements exemplify a high difference in the ozone mea-surement in the lower stratosphere (18ndash32 km) with maxi-mum differences ofminus6 atsim24 km

The earlier reports on SAGE-II measurement illustratedthat the error in ozone retrieval rapidly increases up toapproximately 40 at 10 km (McCormick et al 1989Brinksma et al 2000) which is in accordance with the re-sult presented here Brinksma et al (2000) concluded thatthe SAGE-II ozone measurements become less consistentwith decreasing altitude The inter-comparison study by Luet al (1997) also provided similar results by showing thedifference between HALOE and ozonesonde These differ-ences were found to besim10ndash20 in the 15ndash20 km altituderangesim10 in the 20ndash25 km altitude range andsim1ndash10in the 25ndash30 km altitude range Analogously Cunnold etal (2000) expressed a resembling result when they com-pared the ozonesonde data with SAGE-II and found thatSAGE-II values aresim20ndash30 larger than the ozonesondevalues in the 12ndash15 km altitude range Their observationconcluded that the SAGE-II overestimation is due to aerosolloading in the stratosphere height region and measuremen-tal uncertainties In addition the very low relative differ-ence in ozonesonde data may be due to the lower accuracy ofthe ozone sensor in the stratosphere height region Few pub-lished results on the accuracy of ozonesonde noted that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

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V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

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2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

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V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

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2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

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V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

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aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 2: Stratospheric ozone climatology and variability over a southern

2322 V Sivakumar et al Ozone climatology and variability

most likely caused by biomass burning Their results arein accordance with the observations made over the equato-rial eastern pacific Cristobal Galapagos (09 S 896 W)by Shiotani et al (2002) A review by Staehelin et al (2001)addressed that the satellite and ground-based measurementsshow no significant ozone trends in the tropics but signifi-cant long-term negative trends of 2-4 in the northern andsouthern mid-latitudes Brinksma et al (2002) observed an-nual trends in troposphere-stratosphere ozone variation us-ing five years of ozone measurements from lidar ozonesondeand satellite data over a mid-latitude station Lauder (45 S170 E) They have observed high concentrations during win-ter Using Southern Hemisphere ADditional OZonesonde(SHADOZ) Thompson et al (2003b) presented the tropo-sphere ozone climatology using 3 years of ozonesonde obser-vations for different stations over southern hemisphere Theobservations are concentrated especially over tropicssub-tropical station and noticed a maximum ozone concentrationduring the winterspring period

Although the ozonesonde measurements are precise forthe troposphere and lower stratosphere height regions theyare unable to provide a global picture (Barnes et al 1985Tiao et al 1986) On the other hand satellite measure-ments provide a global coverage with very low frequencyof observation requirements for a particular site The Halo-gen Occultation Experiment (HALOE) on UARS and Strato-spheric Aerosol and Gas Experiment (SAGE) provide a rel-atively better estimation of ozone with good vertical res-olution even at tropospheric altitudes though less in fre-quency of observations for a given site Lu et al (1997) com-pared HALOE SAGE-II and ozonesonde data from Northernhemisphere (Payerne 468 N 695 E) and Southern hemi-sphere (Lauder 450 S 16968 E and Macquarie Island545 S 15895 E) Their studies suggested that HALOESAGE-II and ozonesonde measurements are in good agree-ment especially above 20 km Bhatt et al (1999) concludedthat HALOE is providing accurate ozone profile in the lowerstratosphere whilst the correction for aerosols interferenceis well characterized and when there is no cirrus layers de-tected Newchurch et al (2000) using SAGE-III data forlonger period of about 20 years (1978ndash1998) noted thatthe maximum decline in ozone trends occurred atsim40 kmThe studies further evidenced a large negative trends presentfor the extra-tropics (minus10year) compared to the tropics(minus06year) Dorokhov et al (2002) stated that the compar-ison between satellite and ground-based measurements per-mits a better understanding of the characteristics and weak-ness of each data set

Besides height profiles of ozone the total columns ofozone have been studied by various researchers Chandraet al (1996) presented the mid-latitude total ozone trends inthe northern hemisphere and noticed that they are influencedby inter annual variability which is associated with dynam-ical perturbations in the atmosphere during the winter andspring months They also estimated that due to both radia-

tive and dynamical processes a strong positive correlationbetween total ozone and lower stratospheric temperaturesexists Ziemke and Chandra (1999) discussed the signifi-cance of biomass burning in generating seasonal and zonalanomalies in total ozone over tropics using 20 years of to-tal ozone mapping spectrometer (TOMS) data Their studyillustrated an annual cycle with a maximum ozone concentra-tion during September and October from 15 N to 15 S Thebiomass burning was found to occur at different times fornorthern and southern hemispheres However recent stud-ies based on three-dimensional atmospheric chemistry andtransport models suggest that photochemical ozone forma-tion due to biomass may be less important (Lelieveld andDentener 2000 Marufu et al 2000 Moxim and Levy 2000Chandra et al 2002)

It is apparent from all the above recent studies that thereis considerable interest within scientific community to studythe substantial decreaseincrease in stratospheretroposphereozone Over tropical and sub-tropical regions the ozonemeasurements are very few especially in the southern hemi-sphere (WMO 1999 Staehelin et al 2001) though it hasa significant contribution in the global climate change Re-union Island (21 S 55 E) is located over southern sub-tropics and is influenced by a number of atmospheric per-turbations such as cyclone Inter Tropical Convective Zone(ITCZ) passages strong jet streams etc where the study onozone variations play an important role in addressing dif-ferent aspects of the climate In this study we report onthe climatological characteristics of stratospheric ozone overReunion Island (21 S 55 E) using in-situ ozonesonde data(13 years) and its comparison with UARS-HALOE data (15years) The study also attempted to validate the SAOZ mea-surements taken over Reunion Island by comparing with totalozone measurements from TOMS and those obtained by inte-grating ozonesonde and SAGE-II data (hereafter OAS) Thepaper is organized as follows Sect 2 provides a brief sketchon data used Sect 3 presents the climatological results ob-tained from ozonesonde and HALOE comparison betweenthe ozone measurements from ozonesonde and HALOEtemporal evolution of ozone and anomalies between the mea-surements and comparison of total column ozone measure-ments from TOMS and SAOZ Sect 4 summarizes and con-cludes the results In addition an appendix is included andit provides the monthly mean climatological value of ozoneconcentration and standard deviation over Reunion Island forthe height region from ground to 30 km

2 Data

21 Ozonesonde data

The radiosonde accompanied with Electrochemical Concen-tration Cell (ECC) is used for measuring height profiles ofozone from sea level to about 30 km The radiosondes were

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2323

launched twice a month from September 1992 to December1999 and once a week from January 1999 to at-present Therecorded ozone measurements are converted to concentra-tions (molcm3) and used for the present study The datahas also been collected regularly on both SHADOZ and Net-work for Detection of Atmospheric Composition and Change(NDACC) programmes More details about the data andquality of ozonesonde measurements are found in the liter-ature (Fujiwara et al 2000 Thompson et al 2003a b) andalso specifically for the Reunion ozonesonde measurements(Baldy et al 1996 Randriambelo et al 2000 and Sivakumaret al 2006)

We use 13 years of ozonesonde data gathered fromSeptember 1992 to February 2005 and the height region fromground to 30 km The monthly distributions of data are pre-sented in the Fig 1 (grey colored bars)

22 HALOE-UARS satellite data

HALogen Occultation Experiment (HALOE) was launchedon the Upper Atmosphere Research Satellite (UARS) space-craft on 12 September 1991 as a part of the Earth ScienceEnterprise (ESE) program The experiment uses solar occul-tation to measure the vertical profile of minor constituents(O3 H2O NO2 HCl HF NO and CH4) aerosol concentra-tions and temperature with a height resolution of 37 km foran instantaneous field of view of 16 km at the earth limbIt uses the atmospheric transmission measurements in the28microm CO2 band for the retrieval of ozone mixing ratioThe retrieval method applies a simple ldquoonion-peelrdquo proce-dure to stabilize the height profile at top and bottom The ob-tained ozone profiles are accurate for the height range from10 km to 90 km with a possible error of 5 to 10 More de-tails about HALOE data analysis and quality are discussedin the following literature (eg Russell et al 1993 Ran-del et al 1995 Bruhl et al 1996 Cunnold et al 1996Natarajan and Callis 1997 Grooss et al 1999 and Roodet al 2000 Remsberg et al 2001) and can be cited athttphaloedatalarcnasagovhomeindexphpsite

The present study uses 15 years (September 1991 toFebruary 2005) of data (version 19) acquired during the pas-sage of HALOE satellite over Reunion (21 S 55 E) withlatitudinal and longitudinal discrepancies ofplusmn5 andplusmn25 The monthly distributions of data are sketched in the Fig 1(shaded bars)

23 SAGE-II satellite data

Stratospheric Aerosol and Gas Experiment II (SAGE-II) wasinitiated into the Earth Radiation Budget Satellite (ERBS)in October 1984 The instrument uses the solar occultationtechnique to measure attenuated solar radiation of the Earthrsquoslimb The transmittance measurements are inverted using theldquoonion-peelrdquo approach to yield 1-km vertical resolution pro-files of aerosol extinction ozone nitrogen dioxide and water

Sivakumar et al Stratosphere ozone climatology over Reunion Page 25 of 34

FIGURE-1

Histogram represents the monthly distribution of Ozonesonde HALOE and SAGE-II

satellite data used for the present study and for the period from 1992 to 2005

Fig 1 Histogram represents the monthly distribution ofozonesonde HALOE and SAGE-II satellite data used for thepresent study and for the period from 1992 to 2005

vapour Extensive validation efforts were made to verify theaccuracy of these measurements and the data sets are nowarchived and available for general scientific use More de-tails on SAGE-II data could be found in Attmannspacher etal (1989) and Cunnold et al (1989)

SAGE-II ozone measurements for the height range from05 km to 705 km and for the period from October 1984to February 1999 (sim15 years) is used here The overallconstructed monthly mean profiles are used to merge withdaily ozonesonde measurement so that the ozone profilesextend from 05 km to 705 km and also to allow for thecomputation of the corresponding total columns of ozoneThe monthly distributions of data are presented in the Fig 1(blank bars)

24 TOMS satellite data

Total Ozone Mapping Spectrometer (TOMS) measures thetotal ozone content of the Earthrsquos atmosphere The instru-ment was first launched on the Nimbus 7 Spacecraft in 1978followed by Meteor and Earth Probe The nominal uncertain-ties of TOMS ozone data vary from 1 to 3 Further detailson the TOMS data are available athttptomsgsfcnasagovadeosadeoshtmland McPeters et al (1993)

We use data corresponding to Reunion site (21 S 55 E)obtained from TOMS for the period from July 1996 to De-cember 2004 and the earlier data obtained from NIMBUS-7from January 1978 to June 1996 The data is used to normal-ize the ozone profiles by integrating the ozone measurementsfrom ozonesonde and SAGE-II data (OAS) and also to makea comparison with SAOZ and the total ozone obtained fromOAS

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2324 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 26 of 34

FIGURE-2

Flow diagram represents the procedure followed to obtain the normalized ozone profile

OAS refers to the combined ozonesonde and SAGE-II profile

Daily ozonesonde data for the height range

from 05 km to 30 km

Daily TOMS data over Reunion

Monthly mean

Daily SAGE-II ozone data for the height range from 05 km to 705 km

Monthly mean Step down the height resolution into 1 km

Merging with SAGE-II gives OAS profile

Calculating the integrated ozone

Ratio between the TOMS and OAS total

ozone= Normalization factor

(NF)

Reconstructing the ozone profile by

multiplying the OAS profile by NF

= Normalized ozone profile

Fig 2 Flow diagram represents the procedure followed to ob-tain the normalized ozon profile OAS refers to the combinedozonesonde and SAGE-II profile

25 SAOZ data

The Systeme drsquoAnalyse par Observation Zenithale (SAOZ)instrument is a broad-band (290ndash640 nm) spectrometer andhas undergone various developments since 1988 (Pom-mereau and Piquard 1994) The earlier documents on inter-comparison with different instruments evidenced that thespread in ozone line-of-sight amount is better than 1 (Pom-mereau and Piquard 1994 Hoffman et al 1995 Vaughan etal 1997 Roscoe et al 1999) The vertical columns of ozoneare obtained from the line-of-sight columns and air-mass fac-tor (AMF) using the following relationship

O3(vert)=

(O3(slant) + O3(ref)

)AMF

(1)

Where O3(ref) is the reference ozone spectrum obtainedfrom the spectrometer on a clear day at low solar zenith an-gle Line-of-sight ozone is identified as slant ozone columnO3(slant) and is derived from a spectral band of 100 nm widecentered at 510 nm Real-time and re-analysis SAOZ pro-grams use the standard AMF which is calculated from radia-tive transfer model The value of AMF is found to vary withlatitude and is typically about 12 (ref Sarkissian 1992)

Here the total columns of ozone obtained by SAOZ fromJanuary 1993 to December 2004 are used for comparisonwith both TOMS and the integrated ozone from OAS

3 Results

31 Normalized ozone profile

A height profile of ozone is constructed for the height re-gion from 05 km to 705 km by combining ozonesonde andSAGE-II measurements which are normalized with total col-umn ozone from TOMS data Such profile has been used asa reference for comparing with the other measurements Theroutine adopted to derive the normalized profile is as follows

ndash Daily ozonesonde data is stepped down into 1 km heightresolution

ndash Using 15 years (October 1984 to February 1999) ofSAGE-II data the monthly mean ozone profiles are ob-tained for the height region from 05 km to 705 km

ndash Similarly the monthly mean total ozone values for Re-union Island are derived from 27 years of TOMS mea-surements (from January 1978 to February 2005)

ndash The ozonesonde and SAGE-II monthly mean pro-files (OAS) are merged appropriately for each pro-file at 3 km down to maximum height extended bythe ozonesonde taking into account the measurementerror at the higher heights The SAGE-II monthlymean profiles are correspondingly selected based onthe ozonesonde observational date The merging region(3 km) uses the mean ozone concentrations from SAGE-II and ozonesonde

ndash The above constructed OAS profiles are individuallyintegrated in order to retrieve the corresponding totalozone in terms of Dobson units The normalization fac-tor is defined as the ratio of the OAS total ozone to thecorresponding monthly mean TOMS values

ndash Thus the normalized ozone profile for the height regionfrom 05 km to 705 km is derived by multiplying theOAS profile by normalization factor

The above explained steps are demonstrated in a simplifiedflow chart (see Fig 2) It is also noted here that the cal-culated normalization factor for the complete datasets fromozonesonde SAGE-II and TOMS data is found to vary from102 to 109 with an overall standard deviations ofsim002

32 Height profile of mean ozone

Height profiles of mean ozone concentrations obtained fromozonesonde HALOE and SAGE-II measurements are pre-sented in Fig 3 This figure illustrates the accuracy ofozone measurements obtained from ozonesonde (in-situ)HALOE and SAGE-II satellite data It also validates theozone measurements and illustrates the respective instrumen-tal error and relative measurement differences Here theozonesonde measurements corresponds to the height region

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2325

from 05 km to 295 km and the HALOE and SAGE-II satel-lite data range from 05 km to 705 km Since the height res-olution of the SAGE-II measurements is 1 km the HALOEand ozonesonde data has also been stepped down to 1 km res-olution for uniformity Utilizing the above data the overallmean ozone profiles are constructed individually for eachinstrument irrespective of the year and month

Figure 3a displays the height profiles of ozone concen-trations obtained from ozonesonde SAGE-II and HALOEThe figure is superimposed with the height profile of nor-malized ozone concentrations which were obtained by theabove illustrated method Few differences in values are no-ticed due to different instruments and techniques The nor-malized ozone profiles illustrate a very close agreement be-tween the ozonesonde and SAGE-II satellite data indicatingthat the measurements are consistent The normalized ozoneprofile is in accordance to the ozonesonde measurements inthe lower troposphere and with SAGE-II and HALOE pro-files in the stratosphere up to about 40 km Above 40 kmthe SAGE-II and HALOE measurements indicate very lit-tle discrepancy in the ozone measurements The maximumozone concentrationsim45times1012 molcm3 is displayed by allthe instruments atsim26 km It also shows a small differencein the estimated ozone concentration by instrument SAGE-II and HALOE show similar values and aresim3 higher thanthe ozonesonde It is also clear from the Fig 3a that SAGE-II and HALOE are underestimating the ozone values in thelower tropospheric height region (below 10 km) as expectedfrom the satellite instruments which measure from top to bot-tom and the error increases downward in the troposphere (seealso Fig 3b) Relatively the SAGE-II measurements pro-vide a reasonable comparison with ozonesonde above 12 kmwhen compared to the HALOE which are in agreement above18 km

The relative percentage of deviation (bias) in the ozonemeasurements by ozonesonde HALOE and SAGE-II withrespect to the normalized ozone profile is calculated usingthe following expression

O3(bias) =

(O3(nor) minus O3(xxx)

)O3(nor)

lowast 1000 (2)

Where ldquoO3(xxx)rdquo refers to the ozone measurements fromozonesonde HALOE or SAGE-II

The calculated bias in ozone measurements is presentedin Fig 3b In other words it displays the relative differ-encesuncertainty in the ozone measurements The figuresubstantiates the underestimation of ozone measurements inthe lower troposphere by HALOE and SAGE-II It showsthat the ozone measurements in the troposphere obtainedfrom ozonesonde are having a lower bias than those obtainedfrom HALOE and SAGE-II Just below the ozone maximumheight SAGE-II shows the highest bias while ozonesondereveals the lowest one

The ozonesonde measurements illustrate that the bias iswithin 4ndash6 in the lower troposphere height region and a

Sivakumar et al Stratosphere ozone climatology over Reunion Page 27 of 34

FIGURE ndash 3

(a) Height profile of overall mean ozone concentration obtained from Ozonesonde SAGE-II

and HALOE The figure is superimposed with a normalized ozone concentration

obtained from Ozonesonde and SAGE-II

(b) Height profile of relative percentage of bias in the ozone concentrations measured by

Ozonesonde SAGE-II and HALOE with respect to the normalized ozone profile The

percentage of bias is the ratio between the difference in ozone values and the normalized

ozone profile

Fig 3 (a)Height profile of overall mean ozone concentration ob-tained from ozonesonde SAGE-II and HALOE The figure is su-perimposed with a normalized ozone concentration obtained fromozonesonde and SAGE-II(b) Height profile of relative percent-age of bias in the ozone concentrations measured by ozonesondeSAGE-II and HALOE with respect to the normalized ozone profileThe percentage of bias is the ratio between the difference in ozonevalues and the normalized ozone profile

higher bias of about 10ndash12 is noticed in the upper tro-posphere and lower stratosphere height region (18ndash32 km)Such differences are also remarkably less in comparison withday to day variations (standard deviation) Whereas boththe satellite (HALOE and SAGE-II) measurements demon-strate almost the same magnitude of relative difference andis more than 40 in the lower troposphere However the biasis lower and of almost the same magnitude in the stratosphereheight region (sim above 20 km) The satellite and ozonesondemeasurements exemplify a high difference in the ozone mea-surement in the lower stratosphere (18ndash32 km) with maxi-mum differences ofminus6 atsim24 km

The earlier reports on SAGE-II measurement illustratedthat the error in ozone retrieval rapidly increases up toapproximately 40 at 10 km (McCormick et al 1989Brinksma et al 2000) which is in accordance with the re-sult presented here Brinksma et al (2000) concluded thatthe SAGE-II ozone measurements become less consistentwith decreasing altitude The inter-comparison study by Luet al (1997) also provided similar results by showing thedifference between HALOE and ozonesonde These differ-ences were found to besim10ndash20 in the 15ndash20 km altituderangesim10 in the 20ndash25 km altitude range andsim1ndash10in the 25ndash30 km altitude range Analogously Cunnold etal (2000) expressed a resembling result when they com-pared the ozonesonde data with SAGE-II and found thatSAGE-II values aresim20ndash30 larger than the ozonesondevalues in the 12ndash15 km altitude range Their observationconcluded that the SAGE-II overestimation is due to aerosolloading in the stratosphere height region and measuremen-tal uncertainties In addition the very low relative differ-ence in ozonesonde data may be due to the lower accuracy ofthe ozone sensor in the stratosphere height region Few pub-lished results on the accuracy of ozonesonde noted that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

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V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

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2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

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V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

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2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

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V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

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aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 3: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2323

launched twice a month from September 1992 to December1999 and once a week from January 1999 to at-present Therecorded ozone measurements are converted to concentra-tions (molcm3) and used for the present study The datahas also been collected regularly on both SHADOZ and Net-work for Detection of Atmospheric Composition and Change(NDACC) programmes More details about the data andquality of ozonesonde measurements are found in the liter-ature (Fujiwara et al 2000 Thompson et al 2003a b) andalso specifically for the Reunion ozonesonde measurements(Baldy et al 1996 Randriambelo et al 2000 and Sivakumaret al 2006)

We use 13 years of ozonesonde data gathered fromSeptember 1992 to February 2005 and the height region fromground to 30 km The monthly distributions of data are pre-sented in the Fig 1 (grey colored bars)

22 HALOE-UARS satellite data

HALogen Occultation Experiment (HALOE) was launchedon the Upper Atmosphere Research Satellite (UARS) space-craft on 12 September 1991 as a part of the Earth ScienceEnterprise (ESE) program The experiment uses solar occul-tation to measure the vertical profile of minor constituents(O3 H2O NO2 HCl HF NO and CH4) aerosol concentra-tions and temperature with a height resolution of 37 km foran instantaneous field of view of 16 km at the earth limbIt uses the atmospheric transmission measurements in the28microm CO2 band for the retrieval of ozone mixing ratioThe retrieval method applies a simple ldquoonion-peelrdquo proce-dure to stabilize the height profile at top and bottom The ob-tained ozone profiles are accurate for the height range from10 km to 90 km with a possible error of 5 to 10 More de-tails about HALOE data analysis and quality are discussedin the following literature (eg Russell et al 1993 Ran-del et al 1995 Bruhl et al 1996 Cunnold et al 1996Natarajan and Callis 1997 Grooss et al 1999 and Roodet al 2000 Remsberg et al 2001) and can be cited athttphaloedatalarcnasagovhomeindexphpsite

The present study uses 15 years (September 1991 toFebruary 2005) of data (version 19) acquired during the pas-sage of HALOE satellite over Reunion (21 S 55 E) withlatitudinal and longitudinal discrepancies ofplusmn5 andplusmn25 The monthly distributions of data are sketched in the Fig 1(shaded bars)

23 SAGE-II satellite data

Stratospheric Aerosol and Gas Experiment II (SAGE-II) wasinitiated into the Earth Radiation Budget Satellite (ERBS)in October 1984 The instrument uses the solar occultationtechnique to measure attenuated solar radiation of the Earthrsquoslimb The transmittance measurements are inverted using theldquoonion-peelrdquo approach to yield 1-km vertical resolution pro-files of aerosol extinction ozone nitrogen dioxide and water

Sivakumar et al Stratosphere ozone climatology over Reunion Page 25 of 34

FIGURE-1

Histogram represents the monthly distribution of Ozonesonde HALOE and SAGE-II

satellite data used for the present study and for the period from 1992 to 2005

Fig 1 Histogram represents the monthly distribution ofozonesonde HALOE and SAGE-II satellite data used for thepresent study and for the period from 1992 to 2005

vapour Extensive validation efforts were made to verify theaccuracy of these measurements and the data sets are nowarchived and available for general scientific use More de-tails on SAGE-II data could be found in Attmannspacher etal (1989) and Cunnold et al (1989)

SAGE-II ozone measurements for the height range from05 km to 705 km and for the period from October 1984to February 1999 (sim15 years) is used here The overallconstructed monthly mean profiles are used to merge withdaily ozonesonde measurement so that the ozone profilesextend from 05 km to 705 km and also to allow for thecomputation of the corresponding total columns of ozoneThe monthly distributions of data are presented in the Fig 1(blank bars)

24 TOMS satellite data

Total Ozone Mapping Spectrometer (TOMS) measures thetotal ozone content of the Earthrsquos atmosphere The instru-ment was first launched on the Nimbus 7 Spacecraft in 1978followed by Meteor and Earth Probe The nominal uncertain-ties of TOMS ozone data vary from 1 to 3 Further detailson the TOMS data are available athttptomsgsfcnasagovadeosadeoshtmland McPeters et al (1993)

We use data corresponding to Reunion site (21 S 55 E)obtained from TOMS for the period from July 1996 to De-cember 2004 and the earlier data obtained from NIMBUS-7from January 1978 to June 1996 The data is used to normal-ize the ozone profiles by integrating the ozone measurementsfrom ozonesonde and SAGE-II data (OAS) and also to makea comparison with SAOZ and the total ozone obtained fromOAS

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2324 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 26 of 34

FIGURE-2

Flow diagram represents the procedure followed to obtain the normalized ozone profile

OAS refers to the combined ozonesonde and SAGE-II profile

Daily ozonesonde data for the height range

from 05 km to 30 km

Daily TOMS data over Reunion

Monthly mean

Daily SAGE-II ozone data for the height range from 05 km to 705 km

Monthly mean Step down the height resolution into 1 km

Merging with SAGE-II gives OAS profile

Calculating the integrated ozone

Ratio between the TOMS and OAS total

ozone= Normalization factor

(NF)

Reconstructing the ozone profile by

multiplying the OAS profile by NF

= Normalized ozone profile

Fig 2 Flow diagram represents the procedure followed to ob-tain the normalized ozon profile OAS refers to the combinedozonesonde and SAGE-II profile

25 SAOZ data

The Systeme drsquoAnalyse par Observation Zenithale (SAOZ)instrument is a broad-band (290ndash640 nm) spectrometer andhas undergone various developments since 1988 (Pom-mereau and Piquard 1994) The earlier documents on inter-comparison with different instruments evidenced that thespread in ozone line-of-sight amount is better than 1 (Pom-mereau and Piquard 1994 Hoffman et al 1995 Vaughan etal 1997 Roscoe et al 1999) The vertical columns of ozoneare obtained from the line-of-sight columns and air-mass fac-tor (AMF) using the following relationship

O3(vert)=

(O3(slant) + O3(ref)

)AMF

(1)

Where O3(ref) is the reference ozone spectrum obtainedfrom the spectrometer on a clear day at low solar zenith an-gle Line-of-sight ozone is identified as slant ozone columnO3(slant) and is derived from a spectral band of 100 nm widecentered at 510 nm Real-time and re-analysis SAOZ pro-grams use the standard AMF which is calculated from radia-tive transfer model The value of AMF is found to vary withlatitude and is typically about 12 (ref Sarkissian 1992)

Here the total columns of ozone obtained by SAOZ fromJanuary 1993 to December 2004 are used for comparisonwith both TOMS and the integrated ozone from OAS

3 Results

31 Normalized ozone profile

A height profile of ozone is constructed for the height re-gion from 05 km to 705 km by combining ozonesonde andSAGE-II measurements which are normalized with total col-umn ozone from TOMS data Such profile has been used asa reference for comparing with the other measurements Theroutine adopted to derive the normalized profile is as follows

ndash Daily ozonesonde data is stepped down into 1 km heightresolution

ndash Using 15 years (October 1984 to February 1999) ofSAGE-II data the monthly mean ozone profiles are ob-tained for the height region from 05 km to 705 km

ndash Similarly the monthly mean total ozone values for Re-union Island are derived from 27 years of TOMS mea-surements (from January 1978 to February 2005)

ndash The ozonesonde and SAGE-II monthly mean pro-files (OAS) are merged appropriately for each pro-file at 3 km down to maximum height extended bythe ozonesonde taking into account the measurementerror at the higher heights The SAGE-II monthlymean profiles are correspondingly selected based onthe ozonesonde observational date The merging region(3 km) uses the mean ozone concentrations from SAGE-II and ozonesonde

ndash The above constructed OAS profiles are individuallyintegrated in order to retrieve the corresponding totalozone in terms of Dobson units The normalization fac-tor is defined as the ratio of the OAS total ozone to thecorresponding monthly mean TOMS values

ndash Thus the normalized ozone profile for the height regionfrom 05 km to 705 km is derived by multiplying theOAS profile by normalization factor

The above explained steps are demonstrated in a simplifiedflow chart (see Fig 2) It is also noted here that the cal-culated normalization factor for the complete datasets fromozonesonde SAGE-II and TOMS data is found to vary from102 to 109 with an overall standard deviations ofsim002

32 Height profile of mean ozone

Height profiles of mean ozone concentrations obtained fromozonesonde HALOE and SAGE-II measurements are pre-sented in Fig 3 This figure illustrates the accuracy ofozone measurements obtained from ozonesonde (in-situ)HALOE and SAGE-II satellite data It also validates theozone measurements and illustrates the respective instrumen-tal error and relative measurement differences Here theozonesonde measurements corresponds to the height region

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2325

from 05 km to 295 km and the HALOE and SAGE-II satel-lite data range from 05 km to 705 km Since the height res-olution of the SAGE-II measurements is 1 km the HALOEand ozonesonde data has also been stepped down to 1 km res-olution for uniformity Utilizing the above data the overallmean ozone profiles are constructed individually for eachinstrument irrespective of the year and month

Figure 3a displays the height profiles of ozone concen-trations obtained from ozonesonde SAGE-II and HALOEThe figure is superimposed with the height profile of nor-malized ozone concentrations which were obtained by theabove illustrated method Few differences in values are no-ticed due to different instruments and techniques The nor-malized ozone profiles illustrate a very close agreement be-tween the ozonesonde and SAGE-II satellite data indicatingthat the measurements are consistent The normalized ozoneprofile is in accordance to the ozonesonde measurements inthe lower troposphere and with SAGE-II and HALOE pro-files in the stratosphere up to about 40 km Above 40 kmthe SAGE-II and HALOE measurements indicate very lit-tle discrepancy in the ozone measurements The maximumozone concentrationsim45times1012 molcm3 is displayed by allthe instruments atsim26 km It also shows a small differencein the estimated ozone concentration by instrument SAGE-II and HALOE show similar values and aresim3 higher thanthe ozonesonde It is also clear from the Fig 3a that SAGE-II and HALOE are underestimating the ozone values in thelower tropospheric height region (below 10 km) as expectedfrom the satellite instruments which measure from top to bot-tom and the error increases downward in the troposphere (seealso Fig 3b) Relatively the SAGE-II measurements pro-vide a reasonable comparison with ozonesonde above 12 kmwhen compared to the HALOE which are in agreement above18 km

The relative percentage of deviation (bias) in the ozonemeasurements by ozonesonde HALOE and SAGE-II withrespect to the normalized ozone profile is calculated usingthe following expression

O3(bias) =

(O3(nor) minus O3(xxx)

)O3(nor)

lowast 1000 (2)

Where ldquoO3(xxx)rdquo refers to the ozone measurements fromozonesonde HALOE or SAGE-II

The calculated bias in ozone measurements is presentedin Fig 3b In other words it displays the relative differ-encesuncertainty in the ozone measurements The figuresubstantiates the underestimation of ozone measurements inthe lower troposphere by HALOE and SAGE-II It showsthat the ozone measurements in the troposphere obtainedfrom ozonesonde are having a lower bias than those obtainedfrom HALOE and SAGE-II Just below the ozone maximumheight SAGE-II shows the highest bias while ozonesondereveals the lowest one

The ozonesonde measurements illustrate that the bias iswithin 4ndash6 in the lower troposphere height region and a

Sivakumar et al Stratosphere ozone climatology over Reunion Page 27 of 34

FIGURE ndash 3

(a) Height profile of overall mean ozone concentration obtained from Ozonesonde SAGE-II

and HALOE The figure is superimposed with a normalized ozone concentration

obtained from Ozonesonde and SAGE-II

(b) Height profile of relative percentage of bias in the ozone concentrations measured by

Ozonesonde SAGE-II and HALOE with respect to the normalized ozone profile The

percentage of bias is the ratio between the difference in ozone values and the normalized

ozone profile

Fig 3 (a)Height profile of overall mean ozone concentration ob-tained from ozonesonde SAGE-II and HALOE The figure is su-perimposed with a normalized ozone concentration obtained fromozonesonde and SAGE-II(b) Height profile of relative percent-age of bias in the ozone concentrations measured by ozonesondeSAGE-II and HALOE with respect to the normalized ozone profileThe percentage of bias is the ratio between the difference in ozonevalues and the normalized ozone profile

higher bias of about 10ndash12 is noticed in the upper tro-posphere and lower stratosphere height region (18ndash32 km)Such differences are also remarkably less in comparison withday to day variations (standard deviation) Whereas boththe satellite (HALOE and SAGE-II) measurements demon-strate almost the same magnitude of relative difference andis more than 40 in the lower troposphere However the biasis lower and of almost the same magnitude in the stratosphereheight region (sim above 20 km) The satellite and ozonesondemeasurements exemplify a high difference in the ozone mea-surement in the lower stratosphere (18ndash32 km) with maxi-mum differences ofminus6 atsim24 km

The earlier reports on SAGE-II measurement illustratedthat the error in ozone retrieval rapidly increases up toapproximately 40 at 10 km (McCormick et al 1989Brinksma et al 2000) which is in accordance with the re-sult presented here Brinksma et al (2000) concluded thatthe SAGE-II ozone measurements become less consistentwith decreasing altitude The inter-comparison study by Luet al (1997) also provided similar results by showing thedifference between HALOE and ozonesonde These differ-ences were found to besim10ndash20 in the 15ndash20 km altituderangesim10 in the 20ndash25 km altitude range andsim1ndash10in the 25ndash30 km altitude range Analogously Cunnold etal (2000) expressed a resembling result when they com-pared the ozonesonde data with SAGE-II and found thatSAGE-II values aresim20ndash30 larger than the ozonesondevalues in the 12ndash15 km altitude range Their observationconcluded that the SAGE-II overestimation is due to aerosolloading in the stratosphere height region and measuremen-tal uncertainties In addition the very low relative differ-ence in ozonesonde data may be due to the lower accuracy ofthe ozone sensor in the stratosphere height region Few pub-lished results on the accuracy of ozonesonde noted that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

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Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

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McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 4: Stratospheric ozone climatology and variability over a southern

2324 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 26 of 34

FIGURE-2

Flow diagram represents the procedure followed to obtain the normalized ozone profile

OAS refers to the combined ozonesonde and SAGE-II profile

Daily ozonesonde data for the height range

from 05 km to 30 km

Daily TOMS data over Reunion

Monthly mean

Daily SAGE-II ozone data for the height range from 05 km to 705 km

Monthly mean Step down the height resolution into 1 km

Merging with SAGE-II gives OAS profile

Calculating the integrated ozone

Ratio between the TOMS and OAS total

ozone= Normalization factor

(NF)

Reconstructing the ozone profile by

multiplying the OAS profile by NF

= Normalized ozone profile

Fig 2 Flow diagram represents the procedure followed to ob-tain the normalized ozon profile OAS refers to the combinedozonesonde and SAGE-II profile

25 SAOZ data

The Systeme drsquoAnalyse par Observation Zenithale (SAOZ)instrument is a broad-band (290ndash640 nm) spectrometer andhas undergone various developments since 1988 (Pom-mereau and Piquard 1994) The earlier documents on inter-comparison with different instruments evidenced that thespread in ozone line-of-sight amount is better than 1 (Pom-mereau and Piquard 1994 Hoffman et al 1995 Vaughan etal 1997 Roscoe et al 1999) The vertical columns of ozoneare obtained from the line-of-sight columns and air-mass fac-tor (AMF) using the following relationship

O3(vert)=

(O3(slant) + O3(ref)

)AMF

(1)

Where O3(ref) is the reference ozone spectrum obtainedfrom the spectrometer on a clear day at low solar zenith an-gle Line-of-sight ozone is identified as slant ozone columnO3(slant) and is derived from a spectral band of 100 nm widecentered at 510 nm Real-time and re-analysis SAOZ pro-grams use the standard AMF which is calculated from radia-tive transfer model The value of AMF is found to vary withlatitude and is typically about 12 (ref Sarkissian 1992)

Here the total columns of ozone obtained by SAOZ fromJanuary 1993 to December 2004 are used for comparisonwith both TOMS and the integrated ozone from OAS

3 Results

31 Normalized ozone profile

A height profile of ozone is constructed for the height re-gion from 05 km to 705 km by combining ozonesonde andSAGE-II measurements which are normalized with total col-umn ozone from TOMS data Such profile has been used asa reference for comparing with the other measurements Theroutine adopted to derive the normalized profile is as follows

ndash Daily ozonesonde data is stepped down into 1 km heightresolution

ndash Using 15 years (October 1984 to February 1999) ofSAGE-II data the monthly mean ozone profiles are ob-tained for the height region from 05 km to 705 km

ndash Similarly the monthly mean total ozone values for Re-union Island are derived from 27 years of TOMS mea-surements (from January 1978 to February 2005)

ndash The ozonesonde and SAGE-II monthly mean pro-files (OAS) are merged appropriately for each pro-file at 3 km down to maximum height extended bythe ozonesonde taking into account the measurementerror at the higher heights The SAGE-II monthlymean profiles are correspondingly selected based onthe ozonesonde observational date The merging region(3 km) uses the mean ozone concentrations from SAGE-II and ozonesonde

ndash The above constructed OAS profiles are individuallyintegrated in order to retrieve the corresponding totalozone in terms of Dobson units The normalization fac-tor is defined as the ratio of the OAS total ozone to thecorresponding monthly mean TOMS values

ndash Thus the normalized ozone profile for the height regionfrom 05 km to 705 km is derived by multiplying theOAS profile by normalization factor

The above explained steps are demonstrated in a simplifiedflow chart (see Fig 2) It is also noted here that the cal-culated normalization factor for the complete datasets fromozonesonde SAGE-II and TOMS data is found to vary from102 to 109 with an overall standard deviations ofsim002

32 Height profile of mean ozone

Height profiles of mean ozone concentrations obtained fromozonesonde HALOE and SAGE-II measurements are pre-sented in Fig 3 This figure illustrates the accuracy ofozone measurements obtained from ozonesonde (in-situ)HALOE and SAGE-II satellite data It also validates theozone measurements and illustrates the respective instrumen-tal error and relative measurement differences Here theozonesonde measurements corresponds to the height region

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V Sivakumar et al Ozone climatology and variability 2325

from 05 km to 295 km and the HALOE and SAGE-II satel-lite data range from 05 km to 705 km Since the height res-olution of the SAGE-II measurements is 1 km the HALOEand ozonesonde data has also been stepped down to 1 km res-olution for uniformity Utilizing the above data the overallmean ozone profiles are constructed individually for eachinstrument irrespective of the year and month

Figure 3a displays the height profiles of ozone concen-trations obtained from ozonesonde SAGE-II and HALOEThe figure is superimposed with the height profile of nor-malized ozone concentrations which were obtained by theabove illustrated method Few differences in values are no-ticed due to different instruments and techniques The nor-malized ozone profiles illustrate a very close agreement be-tween the ozonesonde and SAGE-II satellite data indicatingthat the measurements are consistent The normalized ozoneprofile is in accordance to the ozonesonde measurements inthe lower troposphere and with SAGE-II and HALOE pro-files in the stratosphere up to about 40 km Above 40 kmthe SAGE-II and HALOE measurements indicate very lit-tle discrepancy in the ozone measurements The maximumozone concentrationsim45times1012 molcm3 is displayed by allthe instruments atsim26 km It also shows a small differencein the estimated ozone concentration by instrument SAGE-II and HALOE show similar values and aresim3 higher thanthe ozonesonde It is also clear from the Fig 3a that SAGE-II and HALOE are underestimating the ozone values in thelower tropospheric height region (below 10 km) as expectedfrom the satellite instruments which measure from top to bot-tom and the error increases downward in the troposphere (seealso Fig 3b) Relatively the SAGE-II measurements pro-vide a reasonable comparison with ozonesonde above 12 kmwhen compared to the HALOE which are in agreement above18 km

The relative percentage of deviation (bias) in the ozonemeasurements by ozonesonde HALOE and SAGE-II withrespect to the normalized ozone profile is calculated usingthe following expression

O3(bias) =

(O3(nor) minus O3(xxx)

)O3(nor)

lowast 1000 (2)

Where ldquoO3(xxx)rdquo refers to the ozone measurements fromozonesonde HALOE or SAGE-II

The calculated bias in ozone measurements is presentedin Fig 3b In other words it displays the relative differ-encesuncertainty in the ozone measurements The figuresubstantiates the underestimation of ozone measurements inthe lower troposphere by HALOE and SAGE-II It showsthat the ozone measurements in the troposphere obtainedfrom ozonesonde are having a lower bias than those obtainedfrom HALOE and SAGE-II Just below the ozone maximumheight SAGE-II shows the highest bias while ozonesondereveals the lowest one

The ozonesonde measurements illustrate that the bias iswithin 4ndash6 in the lower troposphere height region and a

Sivakumar et al Stratosphere ozone climatology over Reunion Page 27 of 34

FIGURE ndash 3

(a) Height profile of overall mean ozone concentration obtained from Ozonesonde SAGE-II

and HALOE The figure is superimposed with a normalized ozone concentration

obtained from Ozonesonde and SAGE-II

(b) Height profile of relative percentage of bias in the ozone concentrations measured by

Ozonesonde SAGE-II and HALOE with respect to the normalized ozone profile The

percentage of bias is the ratio between the difference in ozone values and the normalized

ozone profile

Fig 3 (a)Height profile of overall mean ozone concentration ob-tained from ozonesonde SAGE-II and HALOE The figure is su-perimposed with a normalized ozone concentration obtained fromozonesonde and SAGE-II(b) Height profile of relative percent-age of bias in the ozone concentrations measured by ozonesondeSAGE-II and HALOE with respect to the normalized ozone profileThe percentage of bias is the ratio between the difference in ozonevalues and the normalized ozone profile

higher bias of about 10ndash12 is noticed in the upper tro-posphere and lower stratosphere height region (18ndash32 km)Such differences are also remarkably less in comparison withday to day variations (standard deviation) Whereas boththe satellite (HALOE and SAGE-II) measurements demon-strate almost the same magnitude of relative difference andis more than 40 in the lower troposphere However the biasis lower and of almost the same magnitude in the stratosphereheight region (sim above 20 km) The satellite and ozonesondemeasurements exemplify a high difference in the ozone mea-surement in the lower stratosphere (18ndash32 km) with maxi-mum differences ofminus6 atsim24 km

The earlier reports on SAGE-II measurement illustratedthat the error in ozone retrieval rapidly increases up toapproximately 40 at 10 km (McCormick et al 1989Brinksma et al 2000) which is in accordance with the re-sult presented here Brinksma et al (2000) concluded thatthe SAGE-II ozone measurements become less consistentwith decreasing altitude The inter-comparison study by Luet al (1997) also provided similar results by showing thedifference between HALOE and ozonesonde These differ-ences were found to besim10ndash20 in the 15ndash20 km altituderangesim10 in the 20ndash25 km altitude range andsim1ndash10in the 25ndash30 km altitude range Analogously Cunnold etal (2000) expressed a resembling result when they com-pared the ozonesonde data with SAGE-II and found thatSAGE-II values aresim20ndash30 larger than the ozonesondevalues in the 12ndash15 km altitude range Their observationconcluded that the SAGE-II overestimation is due to aerosolloading in the stratosphere height region and measuremen-tal uncertainties In addition the very low relative differ-ence in ozonesonde data may be due to the lower accuracy ofthe ozone sensor in the stratosphere height region Few pub-lished results on the accuracy of ozonesonde noted that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 5: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2325

from 05 km to 295 km and the HALOE and SAGE-II satel-lite data range from 05 km to 705 km Since the height res-olution of the SAGE-II measurements is 1 km the HALOEand ozonesonde data has also been stepped down to 1 km res-olution for uniformity Utilizing the above data the overallmean ozone profiles are constructed individually for eachinstrument irrespective of the year and month

Figure 3a displays the height profiles of ozone concen-trations obtained from ozonesonde SAGE-II and HALOEThe figure is superimposed with the height profile of nor-malized ozone concentrations which were obtained by theabove illustrated method Few differences in values are no-ticed due to different instruments and techniques The nor-malized ozone profiles illustrate a very close agreement be-tween the ozonesonde and SAGE-II satellite data indicatingthat the measurements are consistent The normalized ozoneprofile is in accordance to the ozonesonde measurements inthe lower troposphere and with SAGE-II and HALOE pro-files in the stratosphere up to about 40 km Above 40 kmthe SAGE-II and HALOE measurements indicate very lit-tle discrepancy in the ozone measurements The maximumozone concentrationsim45times1012 molcm3 is displayed by allthe instruments atsim26 km It also shows a small differencein the estimated ozone concentration by instrument SAGE-II and HALOE show similar values and aresim3 higher thanthe ozonesonde It is also clear from the Fig 3a that SAGE-II and HALOE are underestimating the ozone values in thelower tropospheric height region (below 10 km) as expectedfrom the satellite instruments which measure from top to bot-tom and the error increases downward in the troposphere (seealso Fig 3b) Relatively the SAGE-II measurements pro-vide a reasonable comparison with ozonesonde above 12 kmwhen compared to the HALOE which are in agreement above18 km

The relative percentage of deviation (bias) in the ozonemeasurements by ozonesonde HALOE and SAGE-II withrespect to the normalized ozone profile is calculated usingthe following expression

O3(bias) =

(O3(nor) minus O3(xxx)

)O3(nor)

lowast 1000 (2)

Where ldquoO3(xxx)rdquo refers to the ozone measurements fromozonesonde HALOE or SAGE-II

The calculated bias in ozone measurements is presentedin Fig 3b In other words it displays the relative differ-encesuncertainty in the ozone measurements The figuresubstantiates the underestimation of ozone measurements inthe lower troposphere by HALOE and SAGE-II It showsthat the ozone measurements in the troposphere obtainedfrom ozonesonde are having a lower bias than those obtainedfrom HALOE and SAGE-II Just below the ozone maximumheight SAGE-II shows the highest bias while ozonesondereveals the lowest one

The ozonesonde measurements illustrate that the bias iswithin 4ndash6 in the lower troposphere height region and a

Sivakumar et al Stratosphere ozone climatology over Reunion Page 27 of 34

FIGURE ndash 3

(a) Height profile of overall mean ozone concentration obtained from Ozonesonde SAGE-II

and HALOE The figure is superimposed with a normalized ozone concentration

obtained from Ozonesonde and SAGE-II

(b) Height profile of relative percentage of bias in the ozone concentrations measured by

Ozonesonde SAGE-II and HALOE with respect to the normalized ozone profile The

percentage of bias is the ratio between the difference in ozone values and the normalized

ozone profile

Fig 3 (a)Height profile of overall mean ozone concentration ob-tained from ozonesonde SAGE-II and HALOE The figure is su-perimposed with a normalized ozone concentration obtained fromozonesonde and SAGE-II(b) Height profile of relative percent-age of bias in the ozone concentrations measured by ozonesondeSAGE-II and HALOE with respect to the normalized ozone profileThe percentage of bias is the ratio between the difference in ozonevalues and the normalized ozone profile

higher bias of about 10ndash12 is noticed in the upper tro-posphere and lower stratosphere height region (18ndash32 km)Such differences are also remarkably less in comparison withday to day variations (standard deviation) Whereas boththe satellite (HALOE and SAGE-II) measurements demon-strate almost the same magnitude of relative difference andis more than 40 in the lower troposphere However the biasis lower and of almost the same magnitude in the stratosphereheight region (sim above 20 km) The satellite and ozonesondemeasurements exemplify a high difference in the ozone mea-surement in the lower stratosphere (18ndash32 km) with maxi-mum differences ofminus6 atsim24 km

The earlier reports on SAGE-II measurement illustratedthat the error in ozone retrieval rapidly increases up toapproximately 40 at 10 km (McCormick et al 1989Brinksma et al 2000) which is in accordance with the re-sult presented here Brinksma et al (2000) concluded thatthe SAGE-II ozone measurements become less consistentwith decreasing altitude The inter-comparison study by Luet al (1997) also provided similar results by showing thedifference between HALOE and ozonesonde These differ-ences were found to besim10ndash20 in the 15ndash20 km altituderangesim10 in the 20ndash25 km altitude range andsim1ndash10in the 25ndash30 km altitude range Analogously Cunnold etal (2000) expressed a resembling result when they com-pared the ozonesonde data with SAGE-II and found thatSAGE-II values aresim20ndash30 larger than the ozonesondevalues in the 12ndash15 km altitude range Their observationconcluded that the SAGE-II overestimation is due to aerosolloading in the stratosphere height region and measuremen-tal uncertainties In addition the very low relative differ-ence in ozonesonde data may be due to the lower accuracy ofthe ozone sensor in the stratosphere height region Few pub-lished results on the accuracy of ozonesonde noted that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

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2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

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V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

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2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

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V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

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Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

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aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

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Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

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2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 6: Stratospheric ozone climatology and variability over a southern

2326 V Sivakumar et al Ozone climatology and variabilitySivakumar et al Stratosphere ozone climatology over Reunion Page 28 of 34

FIGURE ndash 4

(a) Height-Month-mean ozone concentration plot and (b) percentage of deviation

obtained from ozonesonde measurements The percentage of deviation is the ratio

between the obtained standard deviation and the respective monthly mean value

Fig 4 (a) Height-Month-mean ozone concentration plot and(b)percentage of deviation obtained from ozonesonde measurementsThe percentage of deviation is the ratio between the obtained stan-dard deviation and the respective monthly mean value

accuracy of ECC sonde isplusmn5 in the stratosphere region(Beekman et al 1994 Komhyr et al 1995 WMO 1998Logan 1999)

33 Seasonal variation of ozone from ozonesonde data

Since the objective of the paper is to present the stratosphereozone climatology and its variability at a subtropical site(Reunion Island) the monthly mean ozone variations arepresented for the height region from 15 km to 30 km Themonthly mean ozone values are obtained by grouping theozonesonde data in terms of month and irrespective of theyear We also segregated the ozonesonde data by subjectingqualitative analysis (ie withinplusmn2σ ) Hence the data hasbetter accuracy and the obtained monthly mean profiles areaway from the unusual spectacular events (like high ozoneduring STE cyclone planetary wave breaking)

Figure 4a displays the monthly mean variations of ozoneconcentration obtained from ozonesondes for the height re-gion from 15 km to 30 km The vertical ozone variations arein the range from 05times1012 to 45times1012 molcm3 The ozoneconcentration increases gradually to a maximum in the heightrange from 24 to 28 km and then decreases as expected Theannual or semi-annual variation at any particular height re-

gion is not distinguishable but mostly it exhibits an annualvariation with maximum and minimum ozone concentrationsduring springwinter and autumnsummer respectively Inthe Upper troposphere the obtained seasonal variation is inagreement with the earlier reported troposphere ozone clima-tology over Reunion with high- and low-ozone concentra-tions during spring and autumn (Randriambelo et al 2000and Thompson et al 2003b) The result from southern mid-latitude station Lauder (45 S 170 E) also observed the an-nual cycle in upper troposphere ozone densities and statedthat due to ozone production by photochemistry and the min-imum ozone during winter is due to low solar radiation (Fu-jiwara et al 2000) They also stated that the local dynami-cal activities such as monsoon circulations equatorial grav-ity waves Kelvin waves and planetary waves may enhancethe troposphere ozone concentrations The seasonal varia-tion of Reunion stratospheric ozone illustrating increase inspring (see Fig 4a) might be related to wave propagationinto the stratosphere (when winds are westerly) The rela-tion between the ozone concentration and QBO phase (east-erlywesterly) are delineated in detail in the Sect 36 Fur-ther the Fig 4a exemplifies the width of the maximum ozoneconcentration region (sim45times1012 molcm3) which is broadand becomes thinner by September

The ozone variability in terms of percentage of deviationis presented in Fig 4b The percentage of deviation is cal-culated in terms of ratio between the standard deviation andthe respective monthly mean ozone value Broadly the ob-tained seasonal variations in terms of deviations are in therange from 0 to 15 A very low deviation of less than 5 isrecorded for all the months in the height region from 25 kmto 28 km High deviations of aboutsim10ndash15 are obtained inthe height region from 15 to 21 km This height region (15 to21 km) is corresponding to the ozone tropopause where muchvariability in ozone concentration is expected (Sivakumar etal 2006) Above in the middle stratosphere the percentageof deviation is found to be low and a very low deviation (nearto 0) is seen from 25 km to 28 km over all the months Itmay relate to the less fluctuation in ozone concentrations atthis height range

Moreover it is known that variability of stratosphericozone depends on chemical and dynamical processes In-deed with regard to Reunion geographical position inthe southern subtropics nearby dynamic barriers such astropopause and subtropical barrier ozone in the strato-sphere is expected to show high variability due to dynam-ical processes such as stratosphere-troposphere exchangesand meridian exchanges between the stratospheric tropicalreservoir and mid-latitudes as reported by Baray et al (19992000) Bencherif et al (2003) Portafaix et al (2003) andSemane et al (2006) Both of these transport mechanisms(vertical transport through the tropical tropopause and isen-tropic transport nearby the southern subtropical barrier) maybe induced by gravity waves and Rossby planetary wavesbreaking

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V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

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V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

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Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 7: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2327

34 Seasonal variation of ozone HALOE data

The archived 15 years (January 1991 to February 2005)of ozone measurements from HALOE satellite overpassesnearby Reunion Island (21 S 55 E) is grouped in terms ofmonths irrespective of the year Thereafter the correspondingmonthly mean ozone concentrations and the respective rela-tive standard deviations are derived and presented in Fig 5aand b The monthly distribution of data used for constructingthe mean ozone value is displayed in the Fig 1 Figure 5arepresents the monthly variation of ozone nearly similar asdepicted from the ozonesonde measurements (Fig 4a) Heretoo the high ozone value is displayed in the height regionfrom 24 km to 28 km Generally the monthly variations arefound to be smooth in comparison to the ozonesonde mea-surements It could be due to the height resolution of theHALOE data which is high (has an initial vertical resolu-tion of sim37 km) Further the difference in HALOE andozonesonde measurement may be due to the HALOE over-pass location which has the discrepancies ofplusmn5 andplusmn25Above 27 km the estimated ozone concentrations are higherthan the ozonesonde measurements A more detailed sig-nificance of differences in the ozone measurements betweenozonesonde and HALOE are sketched in the following sec-tion (see Sect 35)

Figure 5b renders the obtained standard deviation fromHALOE measurements The percentage of deviations is pre-sented in-terms of ratio between the obtained standard devi-ation and the corresponding monthly mean ozone value Thedeviations are found to be in the range from 0 to 35 Thedeviations are large for height region from 15 km to 20 kmparticularly from 15 km to 18 km The deviation is rela-tively high during January April July and November Atand above 20 km the deviations are smaller in comparisonwith the ozonesonde deviation (Fig 4b) The similarity in themagnitude of the deviation (sim0ndash5) which is noted above21 km as illustrated by ozonesonde measurement furtherproves the accuracy of both instruments The observed largedeviation in the lower height region from 15 km to 18 kmmay be due to the lower accuracy of ozone estimation byHALOE (also see Fig 3b) It is consistent with the report byBorchi et al (2004) revealing that the HALOE measurementsare not reliable for tropical upper troposphere especially be-low 22 km This is also true for the SAGE-II measurements(Morris et al 2002) Bruhl et al (1996) determined that theHALOE ozone mixing ratio may have measurement errors ofabout 30 at 100 hpa and about 8 at 1 hpa pressure levelsAn earlier study on quality of HALOE ozone measurementsin the stratosphere reveals that the uncertainty in measure-ments is due to the forward model which is used to correctozone concentrations retrieval and remove aerosol interfer-ence (Bhatt et al 1999)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 29 of 34

FIGURE ndash 5 same as figure -4 but for the HALOE satellite data Fig 5 Same as Fig 4 but for the HALOE satellite data

35 Difference between ozonesonde and HALOE measure-ments

The percentage of difference between the measured ozoneconcentrations is obtained from ozonesonde and HALOE ob-servations The percentage of difference is calculated withrespect to the ozonesonde observations ie

O3(bias) =

(O3(Sonde) minus O3(Haloe)

)O3(Sonde)

lowast 1000 (3)

Figure 6 represents the obtained percentage of difference be-tween the ozonesonde and HALOE measurements It showsthat for almost all the months the differences vary fromminus20 to +60 with positive and high values between 15 kmand 175 km It further confirms the result obtained from thenormalized profile as depicted in Fig 3b showing the lowaccuracy of HALOE ozone measurements in the upper tro-posphere Lu et al (1997) compared ozone measurementsfrom ozonesonde SAGE-II and HALOE They found a sim-ilar kind of difference in the measurements Their resultepitomized an increase in relative differences with respect toozonesonde with decreasing altitude The differences werefound to be high in the height region from 15 and 20 kmIt might be due to different techniques followed by satelliteand ozonesonde Also their observations illustrated that the

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 8: Stratospheric ozone climatology and variability over a southern

2328 V Sivakumar et al Ozone climatology and variability

Sivakumar et al Stratosphere ozone climatology over Reunion Page 30 of 34

FIGURE - 6

The monthly mean percentage of differences in between HALOE and ozonesonde with respect

to the ozonesonde value

Fig 6 The monthly mean percentage of differences in betweenHALOE and ozonesonde with respect to the ozonesonde value

HALOE data obtained by version 18 is better than that ob-tained by version 17 We have used version 19 of HALOEdata which may further improved the estimation

36 Monthly evolution of ozone and its relation with QBO

The monthly mean ozone concentrations for the periodfrom 1992 to 2004 have been derived from ozonesonde andHALOE data The height-time cross-section of monthlymean ozone concentrations from ozonesonde and HALOEmeasurements are displayed in Fig 7andashb and their corre-sponding percentages of difference with respect to the over-all monthly mean values are presented in Fig 7d and eThe HALOE measurements are presented for the 15ndash45 kmheight region while the ozonesonde measurements are givenbetween 15- and 30-km Generally the mean ozone con-centration from ozonesonde and HALOE are increasing withheight from 15 to 24 km and then decreases above 27 kmThe high ozone concentration is displayed fromsim21 km to27 km with localized maximum value at about 27 km Incomparison to the ozonesonde measurement the HALOEsatellite measurements show modest difference in ozone con-centrations values less thanplusmn5 The low ozone values ob-tained from ozonesonde at higher height regions could bedue to lower measuremental accuracy and the accuracy in-creases with decrease in height The monthly evolutions ofozone concentration represent annual oscillation with max-imum and minimum during May and December monthsIt is also apparent from the figure that the monthly varia-tions of HALOE ozone values are not much different forthe height region from 18 to 21 km when compared with theheight region between 24 and 27 km This may be relatedto (1) the fact that satellite measurements are made follow-ing a downward scan (from top to bottom) (2) to the cor-responding uncertainty increases with decreasing height (3)

Sivakumar et al Stratosphere ozone climatology over Reunion Page 31 of 34

FIGUREndash7 (a-b) Height-time-Monthly evolution of ozone concentrations obtained from the ozonesonde and HALOE measurements

(c) QBO phase illustrated from the zonal mean wind over equator (d-e) the ozone anomalies with respect to the overall monthly mean obtained from the Ozonesonde and HALOE measurements for the period from January 1992 to December 2004

Fig 7 (andashb)Height-time-Monthly evolution of ozone concentra-tions obtained from the ozonesonde and HALOE measurements(c) QBO phase illustrated from the zonal mean wind over equator(dndashe)the ozone anomalies with respect to the overall monthly meanobtained from the ozonesonde and HALOE measurements for theperiod from January 1992 to December 2004

to the relative satellite low resolution and (4) to the possi-ble aerosol interference in O3 values retrieval It is also evi-dent from the Fig 6 that the HALOE under estimates ozoneconcentration in the upper troposphere Though there aregap in the measurements during some yearsmonth and forthe ozonesonde and HALOE both clearly display descend-ingascending trends of in the 20ndash30 km height region Suchvariations are clearer from HALOE measurements than fromozonesonde and it might be caused by quasi-biennial oscilla-tion (QBO) modulation In order to compare the monthlymean ozone values and the ozone anomalies with quasi-biennial oscillation (QBO) structures the zonal mean winddata for the corresponding period is plotted in Fig 7c Weuse zonal wind data obtained at an equatorial site Singapore(130 N 10385 E) The zonal wind data over equator is

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 9: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2329

generally accepted as a representative of the QBO structureand applied by the researchers (see Naujokat 1986) The as-cending descending structure of ozone by ozonesonde mea-surements are found to be related to the easterlywesterlyphase of QBO in some years The years 1999 and 2004 in-dicate the descending structure of ozone with westerly phaseof QBO The year 1998 illustrates the ascending structure ofozone with easterly phase of QBO For all the other yearsthe structure is not very clear from the ozonesonde measure-ment It is almost similar for the HALOE measurements butdue to non-availability of ozone data for intermittent monthsin a year it is not easy to investigate

The percentage of deviations or anomalies is obtained foreach individual month from the monthly mean ozone val-ues with respect to the corresponding monthly climatologicalvalues of ozone With increasing height the percentage ofanomalies is less and highly reduced atsim24 km also both theHALOE and ozonesonde measurements show less bias val-ues withinplusmn10 Both Ozonesonde and HALOE measure-ments show positivenegative deviations for the heights be-lowabove 21 km It is also clear from the figure that the ob-served high anomalies below 21 km are concurrent with thementioned high deviation in the monthly mean ozone valueas demonstrated from Fig 4b Further the positivenegativepercentage of deviations of ozone might be in connectionto the QBO with westerlyeasterly phases It is clearer forthe HALOE measurements than the ozonesonde measure-ments The earlier report from SHADOZ data by Thompsonet al (2003b) observed that the stratospheric ozone profilesdo exhibit QBO cycle

It is also apparent from the figure that neither HALOE norSAGE-II satellite data do not undertake the local-disturbingevent (like convection activities cyclones and etc) whichperturb highly the ozone concentrations Since the main ob-jective of the paper is to provide a picture of the climatolog-ical variation of ozone with height we have not discussedthese events in detail

37 Total ozone and comparison with TOMS and SAOZmeasurements

Here the integrated ozone columns have been obtainedfrom the normalized (the combined ozonesonde and SAGE-II measurement) ozone profile The total ozone time-seriesare presented in Fig 8a and the relative percentages of dif-ferences with respect to the TOMS values are shown inFig 8b The relative percentage of difference is calculatedfor SAOZ and the integrated ozone from OAS with respectto the TOMS data ie

O3(bias) =

(O3(TOMS) minus O3(xxx)

)O3(TOMS)

lowast 1000

The monthly variations in total ozone obtained from the nor-malized profiles (OAS) are mostly closer to TOMS within

Sivakumar et al Stratosphere ozone climatology over Reunion Page 32 of 34

FIGURE ndash 8

(a) Monthly mean evolution of integrated ozone values obtained for the period from

1992 to 2004 by TOMS OAS and SAOZ measurements

(b) The normalized percentage of difference obtained from OAS and SAOZ

measurements with respect to TOMS

Fig 8 (a)Monthly mean evolution of integrated ozone values ob-tained for the period from 1992 to 2004 by TOMS OAS and SAOZmeasurements(b) The normalized percentage of difference ob-tained from OAS and SAOZ measurements with respect to TOMS

plusmn5 The total ozone follows an easy-to-spot annual cy-cle with a maximum during spring (SeptemberndashOctober) anda minimum by early winter (May) Such seasonal varia-tions are consistent with other reported results for southernhemisphere sites (Logan and Kirchhoff 1986 Fishman etal 1990 Kirchhoff et al I991 Kim and Newchurch 1996Fujiwara et al 2003)

The ozonesonde measurement during the initial periodfrom September 1992 to December 1993 shows low ozoneconcentrations (see Fig 8a) It is also noted from Fig 8b(TOMS-OAS differences) that during 1992ndash1995 there is aquite regular decrease Taking into account the latitudinalspread of Pinatubo aerosols notably in the Southern Hemi-sphere and their effects on ozone in the stratosphere one canspeculate that ozone profiles recorded at Reunion highlightthe ozone reduction due to Pinatubo aerosol loading

The SAOZ total ozone measurements nearly follow thatof TOMS but the values are less than TOMS and OAS Theabsence of SAOZ values during September 1996 to August1997 is due to technical changes software and spectrome-ter upgrade The TOMS observation is found to be higherthan the SAOZ and the in-situ observations are in agreementwith earlier documented result from southern high latitudes(Newchurch et al 2000 Kita et al 2000 Bodeker et al2001 Masserot et al 2002) Earlier works indicated thatthe TOMS measurements are approximately 1 higher thanthe average of 30 northern mid-latitude ground-based sta-tions and the discrepancy is higher at southern mid-latitudes(WMO 1999)

Newchurch et al (2000) and Masserot et al (2002) founda significant excess of total ozone of 10ndash15 DU in TOMSmeasurement during cloudy conditions and also investigatedthe incorrect tropospheric ozone climatology dynamical andchemical influences instrument calibration error and the al-gorithm assumption could be the reason for observed excessin TOMS total ozone

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 10: Stratospheric ozone climatology and variability over a southern

2330 V Sivakumar et al Ozone climatology and variability

The Fig 8b illustrates that the percentage of difference iswithin plusmn10 and shows that OAS is in better agreement withTOMS than SAOZ except the post-Pinatubo period (early1992 to 1993 During the initial period of time from 1992to 1994 the OAS expresses a high negative bias more thansim10 (ie the TOMS value is higher than the OAS values)and later we find a nearly positive bias Comparatively theSAOZ measurements display difference in the range ofsim2ndash8 for most of the cases The overall mean difference be-tween TOMS and OAS issim2 DU and for TOMS and SAOZis sim4 DU Thereby it is evident that the OAS is in betteragreement with TOMS than SAOZ This is in accordancewith the statements mentioned in a review article by Stae-helin et al (2001) and a report by Pommereau and Goutail(1988) that the SAOZ measurements are better in the po-lar regions than in the equator as it does not require directsolar radiation and the visible absorption by ozone is muchless temperature dependent than UV absorption A compara-tive study between SAOZ and other techniques reported thatSAOZ is clearly 10ndash15 DU lower than other techniques andattributed the differences to the used AMFrsquos factors (Vaughanet al 1997 Sarkissian et al 1997) The TOMS ozonemeasurement illustrating high values of 1ndash2 DU with OASis in good agreement with the earlier result from WMO (seeWMO 1999) where they found that TOMS measurement is1ndash2 higher in southern low- and mid-latitude regions (Stae-helin et al 2001)

4 Summary and concluding remarks

We presented the general climatalogical characteristics ofstratosphere ozone for a southern sub-tropical site (Re-union Island 21 S 55 E) using large databases of in-situ(ozonesonde and SAOZ) and satellite (HALOE SAGE-II

and TOMS) measurements The ozone measurements byozonesonde HALOE and SAGE-II are in agreement withtheir stated level of uncertainties The largest relative dif-ferences between the satellite and ozonesonde measurementsare found in the height region from 15 km to 20 km sug-gesting the underestimation of ozone by HALOE in the tro-posphere height regions Unambiguously both ozonesondeand HALOE satellite measurements revealed the maximumand minimum ozone concentrations during the springwinterand the autumnsummer months respectively Such depictedmonthly variations of ozone at heights above and below26 km are found to illustrate an opposite cyclic behaviour ofmaximum and minimum ozone concentrations The relativedifference between the HALOE and ozonesonde measure-ments demonstrates a positivenegative values for heightsbelowabove 20 km The monthly temporal variation of theozone concentration for the height region from 15ndash30 kmshows descendingascending trends and which are in rela-tion to the easterlywesterly QBO phase The time evolu-tion of total column ozone obtained from TOMS SAOZozonesonde and SAGE-II (OAS) follows an annual cy-cle with maximum during May-June months Relativelythe total column ozone by TOMS displays a high value incomparison with the SAOZ and the integrated ozone fromozonesonde and SAGE-II The measured OAS total columnozone values are in better agreement with TOMS than SAOZThe above realized results are found to be in better agree-ment with other reported results for southern hemispherersquosmid- and high-latitude stations The added appendix at theend provides the monthly mean ozone concentration and itsstandard deviation for Reunion which can be further consid-ered as a monthly representative one

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 11: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2331

Appendix A

Ozone value for Reunion

Table A1 Monthly mean (times1012molcm3)

Height Jan Feb March April May June July Aug Sep Oct Nov Dec(km)

1 043 044 045 053 057 067 066 063 068 064 053 0472 044 047 047 054 058 067 069 070 070 067 056 0563 057 060 057 059 059 067 066 076 083 084 077 0714 070 058 067 071 058 067 069 084 086 095 093 0795 062 061 068 066 061 067 067 083 086 095 089 0866 063 066 067 069 057 067 066 086 083 091 083 0867 062 064 063 064 057 065 073 069 076 081 085 0748 068 058 054 060 057 058 070 068 072 082 081 0689 064 059 049 054 053 052 059 063 070 078 074 06810 047 047 044 049 052 053 054 057 064 069 072 06011 048 040 039 047 046 049 047 046 056 051 058 05212 038 037 038 045 045 045 036 044 053 055 053 04313 039 037 038 042 040 042 035 039 042 048 050 04614 039 041 038 041 037 042 040 040 039 051 050 04015 042 045 045 040 039 043 039 044 041 049 049 04316 045 039 045 043 039 048 049 052 048 050 052 04917 052 052 049 050 044 049 055 062 066 063 062 05518 082 079 072 067 065 069 072 081 097 096 098 08919 137 131 128 123 120 143 146 156 171 172 161 15520 201 182 191 198 192 208 223 238 247 259 254 23821 274 255 252 268 257 295 307 300 295 315 304 30722 332 310 316 307 313 339 360 373 349 371 355 34623 378 370 362 369 385 380 408 411 382 414 406 39824 409 412 407 420 421 438 443 454 437 446 439 43125 434 441 439 450 442 444 454 443 435 452 445 43926 437 444 446 445 445 438 433 424 424 438 438 44527 436 431 443 436 435 421 399 390 391 423 424 43228 408 410 416 397 405 371 358 349 357 385 404 40429 378 382 376 362 345 325 340 316 328 368 364 35830 328 345 332 321 296 273 292 280 300 326 333 327

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 12: Stratospheric ozone climatology and variability over a southern

2332 V Sivakumar et al Ozone climatology and variability

Table A2 (b) Standard deviation (times1012molcm3)

Height Jan Feb Mar April May June July Aug Sep Oct Nov Dec(km)

1 007 007 007 006 004 005 006 003 003 006 009 0092 005 007 005 007 003 004 005 007 006 005 007 0093 010 010 007 010 007 006 009 016 010 006 008 0134 012 006 009 008 007 008 011 008 013 006 007 0145 010 010 011 012 007 009 007 011 012 005 010 0126 012 010 010 007 007 010 008 009 013 005 010 0087 009 012 009 006 006 011 009 010 013 006 007 0128 011 010 007 005 008 008 006 007 010 008 006 0139 010 010 009 008 008 008 008 006 009 008 008 01110 011 009 007 005 014 009 009 009 009 010 003 01111 011 008 004 008 009 006 007 010 007 013 005 01012 008 009 008 011 012 005 007 004 007 006 004 00713 008 008 008 009 009 005 006 006 008 008 008 00914 008 006 007 004 006 005 005 008 004 004 003 00815 006 005 007 006 004 005 006 006 005 005 004 00816 007 004 004 005 004 005 008 004 005 007 005 00717 008 006 007 007 003 007 007 009 007 008 012 00918 009 009 011 009 006 011 010 006 015 011 011 01419 021 015 013 011 006 020 023 019 008 013 011 01920 019 011 015 023 016 036 027 028 024 022 021 03221 015 015 013 019 018 034 024 027 034 027 023 02622 020 013 013 012 017 036 014 028 031 026 022 02823 019 014 014 012 022 022 024 030 038 019 016 02024 022 019 016 017 024 013 021 016 031 016 016 01825 018 011 015 014 014 013 013 013 015 014 012 01826 016 011 017 017 015 022 022 016 015 015 010 01527 016 010 013 015 017 020 025 018 015 023 011 01428 015 016 016 028 021 027 018 015 018 030 013 01829 017 014 020 029 033 017 029 009 021 027 016 01730 015 015 021 025 028 018 030 006 036 027 022 020

AcknowledgementsLaboratoire de lrsquoAtmosphere et des Cyclones(LACy) is supported by the French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) and the Conseil Regional de la Reunion INSUCNRSand SHADOZNASA programs financially support the Radiosondelaunching One of the authors VSK acknowledges ConseilRegional de la Reunion and French Centre National de la RechercheScientifique (CNRS)Institut National des Sciences de lrsquoUnivers(INSU) for the financial grant obtained under the post-doctoral fel-lowship scheme We are also grateful to the LACy radio-soundingteam (especially F Posny J-M Metzger and G Bain) for their con-stant co-operation in launching radiosondes Authors are thankfulto the Upper Atmosphere Research Satellite (UARS) Project (Code916) and the Distributed Active Archive Center (Code 902) at theGoddard Space Flight Center Greenbelt MD 20771 for provid-ing HALOE satellite data through the web sitehttphaloedatalarcnasagovhomeindexphp We also express our thanks to SAGE-IITOMS and SAOZ data centres for providing access to the data

Topical Editor F DrsquoAndrea thanks two anonymous referees fortheir help in evaluating this paper

References

Attmannspacher W Noe J Muer D Lenoble J Megie GPelon J Pruvost P and Reiter R European Validation ofSAGE II Ozone Profiles J Geophys Res 94 8461ndash8466 1989

Baldy S Ancellet G Bessafi M Badr A and Lan Sun Luk DField observations of the vertical distributions of troposphericozone at the island of la reunion (southern tropics) J GeophysRes 101 23 835ndash23 849 1996

Baray J-L Ancellet G Randriambello T and Baldy S Trop-ical cyclone marlene and stratosphere-troposphere exchange JGeophys Res 104 13 953ndash13 970 1999

Baray J-L Daniel V Ancellet G and Legras B Planetary-scale tropopause folds in the southern subtropics Geophys ResLett 27 353ndash356 2000

Barnes R A Bandy A R and Torres A L Electrochemicalconcentration cell ozonesonde accuracy and precision J Geo-phys Res 90 7881ndash7887 1985

Bencherif H Portafaix T Baray J-L Morel B Baldy S Lev-eau J Hauchecorne A Keckhut P Moorgawa A MichaelisM and Diab R Lidar observations of lower stratospheric

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 13: Stratospheric ozone climatology and variability over a southern

V Sivakumar et al Ozone climatology and variability 2333

aerosols over South Africa linked to large scale transport acrossthe southern subtropical barrier J Atmos Solar Terr Phys 65707ndash715 2003

Beekmann M Ancellet G Megie G Smit J H G and KleyD Inter comparison campaign including electrochemicals son-des of ECC and Brewer-Mast type and a ground based UV-differential absorption lidar J Atmos Chem 19 259ndash2881994

Bhatt P P Remsberg E E Gordley L L McInerney J MBracket V G and Russel III J M An evaluation of the qualityof Halogen Occultation Experiment ozone profiles in the lowerstratosphere J Geophys Res 104 9261ndash9275 1999

Bodeker G E Scott J C Kreher K and McKenzie R LGlobal ozone trends in potential vorticity coordinates usingTOMS and GOME intercompared against the Dobson network1978ndash1998 J Geophys Res 19 23 029ndash23 042 2001

Borchi F Pommereau J-P Garnier A and Pinharanda MEvaluation of SHADOZ sondes HALOE and SAGE II ozoneprofiles at the tropics from SAOZ UV-Vis remote measurementsonboard long duration balloons Atmos Chem Phys Discuss4 4945ndash4997 2004httpwwwatmos-chem-phys-discussnet449452004

Brinksma E J Bergwerff J B Bodeker G E Boersma K FBoyd I S Connor B J Hann J F Hogervorst W HovenierJ W Parrish A Tsou J J Zawodny J M and Swart D PJ Validation of 3 years of ozone measurements over Networkfor the Detection of Stratospheric Change station Lauder NewZealand J Geophys Res 105 17 291ndash17 306 2000

Brinksma E J Ajtic J Bergwerff J B Bodeker G EBoyd I S Haan J F Hogervorst W Hovernier J W andSwart D P J Five years of observations of ozone profilesover Lauder New Zealand J Geophys Res 107(D14) 4216doi1010292001JD000737 2002

Bruhl C Drayson S R Russell III J M Crutzen P J McIn-erney J Purcell P N Claude H Gernand H McGee TMcDermid I and Gunson M R HALOE Ozone Channel Val-idation J Geophys Res 101 10 217ndash10 240 1996

Chandra S Varotsos C and Flynn L E The mid-latitude totalozone trends in the northern hemisphere Geophys Res Lett 23555ndash558 1996

Chandra S Ziemke J R Bhartia P K and Martin RV Tropical tropospheric ozone Implications for dynam-ics and biomass burning J Geophys Res 107(D14) 4188doi1010292001JD000447 2002

Cunnold D M Chu W P Barnes R A McCormick M P andVeiga R E Validation of SAGE II Ozone Measurements JGeophys Res 94 8447ndash8460 1989

Cunnold D M Froidevaux L Russell III J M Connor B Jand Roche A E Overview of UARS Ozone Validation BasedPrimarily on Intercomparisons Among UARS and SAGE II Mea-surements J Geophys Res 101 10 335ndash10 350 1996

Cunnold D M Newchurch M J Flynn L E Wang H J Rus-sell J M McPeters R Zawodny J M and Froidevaux LUncertainties in upper stratospheric ozone trends from 1979 to1996 J Geophys Res 105 4427ndash4444 2000

Dorokhov V M Khaikin S M and Igantiev D V Observationsof ozone variability over eastern Siberia Yakutsk 1992ndash2002Air pollution research report 79 Proceedings of the 6th Euro-pean symposium 128ndash131 2002

Fishman J Watson C E Larsen J C and Logan J A Dis-tribution of tropospheric ozone determined from satellite data JGeophys Res 95 3599ndash3617 1990

Fujiwara M Kita K Ogawa T Kawakami S Sano T Ko-mala N Saraspriya S and Suripto A Seasonal variations oftropospheric ozone in Indonesia revealed by 5-year ground-basedobservations J Geophys Res 105 1879ndash1888 2000

Fujiwara M Tomikawa Y Kita K Kondo Y Komala NSaraspriya S Manki T Suripto A Kawakami S OgawaT Kelana E Suhardi B Harijono S W B Kudsy M Sribi-mawati T and Yamanaka M D Ozonesonde observations inthe Indonesian maritime continent a case study on ozone richlayer in the equatorial upper troposphere Atmos Environ 37353ndash362 2003

Grooss J-U Mueller R Becker G McKenna D S andCrutzen P J The upper stratospheric ozone budget An up-date of calculations based on HALOE data J Atmos Chem34 171ndash183 1999

Hoffman D J Bonasoni P De Maziere M et al Intercom-parison of UVvisible spectrometers for measurements of strato-spheric NO2 for the Network for the Detection of StratosphericChanges J Geophy Res 100 16 765ndash16 791 1995

Kim J H and Newchurch M J Climatology and trends of tro-pospheric ozone over the eastern Pacific Ocean The influencesof biomass burning and tropospheric dynamics Geophys ResLett 23 3723ndash3726 1996

Kirchhoff V W J H Barnes R A and Torres A L Ozoneclimatology at Natal Brazil from in situ ozonesonde data JGeophys Res 96 10 899ndash10 909 1991

Kita K Fujiwara M and Kawakami S Total Ozone increaseassociated with forest fires over the Indonesian region and its re-lation to the EI Nino-Southern Oscillation Atmos Environ 342681ndash2690 2000

Komhyr W D Barnes R A Brothers G B Lathrop JA and Opperman D P Electrochemical concentration cellozonesonde performance evaluation during STOIC 1989 J Geo-phys Res 100 9231ndash9244 1995

Lelieveld J and Dentener F J What controls troposphericozone J Geophys Res 105 3531ndash3551 2000

Logan JA and Kirchhoff VWJH Seasonal variations of tropo-spheric ozone at Natal Brazil J Geophys Res 91 7876-78811986

Logan J A An analysis of ozonesonde data for the lower strato-sphere Recommendations for testing models J Geophys Res104 16 151ndash16 170 1999

Lu J Mohnen V A Yue G K Atkinson R J and MatthewsW A Intercomparison of stratospheric ozone profiles obtainedby stratospheric aerosol and gas experiment II Halogen Occulta-tion Experiment and ozonesondes in 1994ndash95 J Geophys Res102 16 137ndash16 144 1997

Marufu L Dentener F Lelieveled J Andreae M O andHelas G Photochemistry of the African troposphere Influenceof biomass burning emission J Geophys Res 104 14 513ndash14 530 2000

Masserot D Lenoble J Brogniez C Houet M KrotkovN and McPeters R Retrieval of ozone column from globalirradiance measurements and comparison with TOMS dataA year of data in the Alps Geophys Res Lett 29 1309doi1010292002GL014823 2002

wwwann-geophysnet2523212007 Ann Geophys 25 2321ndash2334 2007

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007

Page 14: Stratospheric ozone climatology and variability over a southern

2334 V Sivakumar et al Ozone climatology and variability

McPeters R D Kruegar A J Bharatia P K Herman JR Ozkes A Ahmad Z Cebula R P Schlesinger B MSwissler T Taylor S L Torres O and Wellemeyer C GNimbus-7 total ozone mapping spectrometer (TOMS) data prod-ucts userrsquos guide NASA Ref Pub 1323 1993

McCormick M P Zawodny J M Veiga R E Larsen J Cand Wang P H An overview of SAGE I and SAGE II ozonemeasurements Planet Space Sci 37 1567ndash1586 1989

Morris G A Gleason J F Russell III J M Schoeberl MR and McCornick M P A comparison of HALOE V19 withSAGE II V600 ozone observations using trajectory mapping JGeophys Res 107 4177 doi1010292001JD000847 2002

Moxim W J and Levy II H A model analysis of tropical SouthAtlantic Ocean tropospheric ozone maximum The interaction oftransport and chemistry J Geophys Res 104 17 393ndash17 4152000

Naujokat B An update of the observed quasi-biennial oscillationof the stratospheric winds over the tropics J Atmos Sci 431873ndash1877 1986

Natarajan M and Callis L B Ozone Variability in the High Lati-tude Summer Stratosphere Geophys Res Lett 24 1191ndash11941997

Newchurch M J Bishop L Cunnold D et al Upper-stratospheric ozone trends 1979ndash1998 J Geophys Res 10514 625ndash14 636 2000

Pommereau J P and Goutail F O3 and NO2ground-basedmeasurements by visible spectrometry during arctic winter andspring 1988 Geophys Res Lett 15 891ndash894 1988

Pommereau J P and Piquard J Ozone nitrogen dioxide andaerosol vertical distribution by UV-visible solar occultation fromballoons Geophys Res Lett 21 1227ndash1230 1994

Portafaix T Morel B Bencherif H Baldy S Godin-Beekmann S and Hauchecorne A Fine-scale study of athick stratospheric ozone lamina at the edge of the south-ern subtropical barrier J Geophys Res 108(D6) 4196doi1010292002JD002741 2003

Randel W J Wu F Russell III J M Waters J W and Froide-vaux L Ozone and Temperature Changes in the StratosphereFollowing the Eruption of Mt Pinatubo J Geophys Res 10016 753ndash16 764 1995

Randriambelo T Baray J-L and Baldy S Effect of biomassburning convective venting and transport on tropospheric ozoneover the Indian Ocean Reunion Island field observations J Geo-phys Res 105 11 813ndash11 832 2000

Remsberg E Bhatt P and Deaver L E Ozone changes in thelower stratosphere from the halogen occultation experiment for1991 through 1999 J Geophys Res 106 1639ndash1653 2001

Rood R B Douglass A R Cerniglia M C Sparling L C andNielsen J E Seasonal variability of middle-latitude ozone inthe lowermost stratosphere derived from probability distributionfunctions J Geophys Res 105 17 793ndash17 805 2000

Roscoe H K Johnston P V Van Roozendael M et al Slantcolumn measurements of O3 and NO2 during the NDSC inter-comparison of zenith-sky UV-visible spectrometers in june 1996J Atmos Chem 32 281-314 1999

Russell III J M Gordley L L Park J H Drayson S R Hes-keth W D Cierone R J Tuck A F Frederick J E HarriesJ E and Crutzen P J The Halogen Occultation Experiment J

Geophys Res 98 10 777ndash10 797 1993Sarkissian A Observation depuis le sol des nuages et des

poussieres dans lrsquoatmosphere Applications a la stratospherepolaire et a lrsquoatmosphere de Mars These de Doctorat delrsquoUniversite Paris 6 1992

Sarkissian A Vaughan G Roscoc H K Bartlett L M ConnorF M O Drew D G Hughes PA and Moore D M Accu-racy of measurements of total ozone by a SAOZ ground-basedzenith sky visible spectrometer J Geophys Res 102 1379ndash1390 1997

Semane N Bencherif H Morel B Hauchecorne A and DiabR D An unusual stratospheric ozone decrease in the southernhemisphere subtropics linked to isentropic air-mass transport asobserved over Irene (255 S 281 E) in mid-May 2002 AtmosChem Phys 6 1927ndash1936 2006httpwwwatmos-chem-physnet619272006

Shiotani M Fujiwara M Hashizume H Vomel H Oltmans SJ and Watanabe T Ozonesonde Observations in the EquatorialEastern Pacific ndash the Soyo-Maru Survey J Met Soc Japan 88897ndash909 2002

Sivakumar V Baray J-L Baldy S and Bencherif HTropopause characteristics over a southern sub-tropical site Re-union Island (21 S 55 E) using RadiosondeOzonesonde dataJ Geophys Res 111 D19111 doi1010292005JD0064302006

Staehelin J N Harris R P Appenzeller C and Eberhard JOzone trends A review Rev Geophys 39 231ndash290 2001

Thompson A M Witte J C McPeters R D Oltmans S JSchmidlin F J Logan J A Fujiwara M Kirchhoff V WJ H Posny F Coetzee G J R Hoegger B Kawakami SOgawa T Johnson J B Vomel H and Labow G SouthernHemisphere Additional Ozonesondes (SHADOZ) 1998ndash2000tropical ozone climatology 1 Comparison with Total OzoneMapping Spectrometer (TOMS) and ground-based measure-ments J Geophys Res 108 8238 doi1010292001JD0009672003a

Thompson A M Witte J C Oltmans S J Schmidlin F JLogan J A Fujiwara M Kirchhoff V W J H Posny FCoetzee G J R Hoegger B Kawakami S Ogawa T For-tuin J P F and Kelder H M Southern Hemisphere AdditionalOzonesondes (SHADOZ) 1998ndash2000 tropical ozone climatology2 Tropospheric variability and the zonal wave-one J GeophysRes 108 8241 doi1010292002JD002241 2003b

Tiao G C Reinsel G C Pedrick J H Allenby G M MateerC L Miller A J and DeLuisi J J A statistical trend analysisof ozonesonde data J Geophys Res 91 13 121ndash13 136 1986

Vaughan G Roscoe H K Bartlett L M et al An intercom-parison of ground-based UV-visible sensors of ozone and NO2J Geophys Res 102 1411ndash1422 1997

WMO (World Meterological Organisation) SPARCIOCGAWAssessment of trends in the vertical distribution of ozone editedby Harris N Hudson R and Phillips C SPARC report N1WMO Ozone research and monitoring project Rep 43 1998

WMO Scientific Assessment of Ozone Depletion 1998 Rep 44Global Ozone Res and Monit Proj Geneva 1999

Ziemke J R and Chandra S Seasonal and interannual vari-abilities in tropical tropospheric ozone J Geophys Res 10421 425ndash21 442 1999

Ann Geophys 25 2321ndash2334 2007 wwwann-geophysnet2523212007