vertical ozone change workshop, geneva, 2011 sciamachy limb ozone profiles c. von savigny, a....

Vertical ozone change workshop, Geneva, 2011

SCIAMACHY limb ozone profilesSCIAMACHY limb ozone profiles

C. von Savigny, A. Rozanov, M. Weber, S. Mieruch, N. Rahpoe, H. Bovensmann and J. P. Burrows

Institute of Environmental Physics, University of Bremen, Bremen, Germany

Contact: [email protected]

Workshop on Past Changes in the vertical distribution of ozoneWorkshop on Past Changes in the vertical distribution of ozoneGeneva, January 25 – 27, 2011


SCIAMACHY on Envisat

• Launch date: February 28, 2002• Polar, sun-synchronous orbit • Descending node: 10:00 LST• Altitude: 800 (783) km

Features:• UV/Vis/NIR grating spectrometers:

220 - 2380 nm• Moderate spectral resolution:

0.2 – 1.5 nm• Measurement Geometries:

SCIAMACHY = SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY


• Tangent height range: 0 to 92 (105) km

• Tangent height step size: 3.3 km

• Vertical FOV: 2.6 km

• Observations optimised for limb-nadir matching

• Duration of Limb sequence: 60 s

• Observed is limb scattered solar radiation and terrestrial airglow emissions

• On the Earth’s night side limb emissions are observed in a dedicated mesosphere/ thermosphere observation mode with tangent height between 75 and 150 km.

SCIAMACHY Limb observations

Illustration of the limb-scattering geometry


O3 profile retrieval algorithm


• Simultaneous retrieval in Hartley, Huggins and Chappuis bands (Current version Stratozone 2.3)

• Wavelength triplet in Chappuis-bands: 525 nm, 600 nm 675 nm [Flittner et al., 2000; von Savigny, 2002]

• Wavelet singlets in Hartley-Huggins-bands [Rohen,2006]

Methodology

(GOME FM O3 absorption cross section Burrows et al. [1999])


Step 1: Tangent height Normalization

Methodology

Step 2: Form Chappuis-triplet (Flittner, 2000; von Savigny, 2002)

Wavelengths (nm) 264 267.5 273.5 283 286 288 290 305 525 602 675THlow (km) 52 52 52 45 45 45 45 35 9 9 9THref (km) 71 71 71 68 65 65 61 55 41 41 41

Then construct retrieval vector:

I: Limb radianceTH: tangent heightTHref: reference tangent heightk: wavelength index (k [1,11])


Feature Additional remarksRetrieved quantity O3 concentrationAltitude grid Regular 1 km grid (10 – 80 km)Inversion scheme Iterative Gauss-Newton Weak statistical contraint and

smoothness constraintRadiative Transfer Model SCIATRAN version 3.1Weighting function calculation

Analytically in single-scattering mode

Vertical resolution About 4 km between 15 and 65 km altitude

Averaging kernels for every retrieved profiles available

Level 1 data used Version 6.03 or higher Including AUX_FRA platform attitude correction files as well as SCIAMACHY

extra misalignment correctionBackground atmosphere 6-hourly pressure & temperature

data from ECMWF analysesStratospheric aerosol extinction profiles

ECSTRA aerosol extinction data base [Bingen and Fussen, 2000]

Using climatological NCEP tropopause height

Stratospheric aerosol phase function

Henyey-Greenstein with g 0.7

Surface albedo data Matthews [1984] data baseO3 X-sections Bogumil Version 2.0 SCIAMACHY FM X-sectionsPointing correction No additional pointing correctionCloud flagging Tropospheric, stratospheric and

mesospheric clouds are detected Cloud flags provided in O3 Level 2 data

Features of version 2.3 O3 profiles


What are the main error sources?von Savigny et al. [2005]

Uncertainties in knowledge of stratospheric aerosols

Tangent height errors

Note: Sensitivity studies done for OSIRIS Chappuis-band retrievalBut: Basic sensitivities are similar for SCIAMACHY

Comprehensive sensitivity analysis for extended SCIAMACHY retrieval currently underway within ESA-CCI project


Open issues / features to be implemented

• TH registration issues not completely solved ( more on following slides)

• Implementation of effective albedo retrieval underway

• Stratospheric aerosol extinction profile retrieval from SCIAMACHY limb observations implemented, testing ongoing.

Eventually, these aerosol retrievals will be used for the O3 profile retrievals


SCIAMACHY IUP O3 profile data set (version 2.0) was already used in 2 ozone trend studies


Adapted from Steinbrecht et al., Ozone and temperature trends in the upper stratosphere at five stations of the Network for the Detection of Atmospheric Composition Change, Int. J. Rem. Sens. [2009]

Long-term trends in stratospheric O3


SCIAMACHY

OSIRIS/Odin

SMR/Odin

HALOE

SAGE I + II

SBUV/2

All instrument average

Jones et al., Evolution of stratospheric ozone and water vapour time series studied with satellite measurements, Atmos. Chem. Phys. 9, 6055 – 6075, 2009.

Long-term trends in stratospheric O3


• Determination of “instrument drift” for each instrument :

“Instrumental drifts” established by Jones et al. [2009]


Tangent height retrievals from SCIAMACHY limb-radiance profile observations in the UV


TRUE = Tangent height Retrieval by UV-B Exploitation

• TRUE [Kaiser et al., 2004] exploits the maximum (”knee”) in the UV limb radiance profiles caused by the absorption in the Huggins- and Hartley-bands of O3.

Technical features of TRUE (vs 1.8):• IUP dynamical O3 climatology [Lamsal et al., 2003] together with EP-TOMS and

OMI Total ozone column (TOC) data for each day and location. Climatological O3 profiles scaled to TOC value.

• Use of ECMWF background atmosphere for date, time and coordinates of every SCIAMACHY limb state analyzed


Monthly mean tropical (25° S – 25° N) TH offsets

Definition: TH offset = Level 1 TH – TRUE TH


Monthly mean tropical L1 version 7.03 TH offsets

Trend: -54 m/year


Tangent height trends derived from solar occultations

• Solar occultation observations only at mid/high northern latitudes (50° – 70° N)

• Tangent height offset derived from position retrievals using scans across solar disk

• Linear trend from 2002 to mid-2006: about -20 m /year

TH (L

evel

1) –

TH

(ret

rieve

d) [k

m]

Year

Data provided by K

laus B

ramstedt (IU

P B

remen)


Current validation and trend study results


Validation of SCIAMACHY vs. 2.1 ozone profiles

MLS

SAGE II

ACE-FTS

SABER

HALOE

Mieruch et al., about to be subm

itted to JGR

[2011]

Version 6.2

Version 2.2

Version 2.2

Version 1.07Thermal IR

Version 19


Mieruch et al., [2011]

Validation of SCIAMACHY vs. 2.1 ozone profiles


• Model includes: constant term, linear trend, annual, semi-annual and QBO- components• Thick black lines indicate areas where trends are significant at the 95%

confidence level (Following Weatherhead et al. [1998])

Note: SAGE (2002 – 2005), HALOE (2002 – 2005), ACE-FTS (2004 – 2008) do not show statistically significant trends (with very few exceptions)

Trend analysis M

ieruch et al., [2011]

No statistically significant trends detected for 2004 – 2008 !

Trends in % / year


Conclusions

• IUP SCIAMACHY O3 profile data set (15 – 70 km) available since August 2002 to date and accessible through: www.iup.uni-bremen.de/scia-arc/

• Overall agreement with SAGE II, HALOE and ACE-FTS within 10% between 20 and 50 km altitude• Compilation of comprehensive error budget for IUP Bremen SCIAMACHY limb

ozone profile data set ongoing within ESA’s Ozone-CCIESA’s Ozone-CCI project• Comparisons with independent satellite data sets and trend analyses indicate

anomalous trend in SCIAMACHY O3 concentrations, likely related to trends in pointing information• Characterization and correction of pointing trends ongoing• ESA currently plans to shut down Envisat in December 2013 (summer 2014 at latest)• Further continuation of Envisat chemistry observations highly desirable

Acknowledgements

SCIAMACHY is jointly funded by Germany, the Netherlands and Belgium. SCIAMACHY Level 1 data were provided by ESA. Funding for the presented investigations is provided by ESA, the German Ministry of Education and Research BMBF, the German Aerospace Center DLR and the University of Bremen. We are indebted to all members of the SCIAMACHY team whose efforts made this analysis possible.

vertical ozone change workshop, geneva, 2011 sciamachy limb ozone profiles c. von savigny, a....

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