vertical ozone change workshop, geneva, 2011 sciamachy limb ozone profiles c. von savigny, a....
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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: csavigny@iup.physik.uni-bremen.de
Workshop on Past Changes in the vertical distribution of ozoneWorkshop on Past Changes in the vertical distribution of ozoneGeneva, January 25 – 27, 2011
Vertical ozone change workshop, Geneva, 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
Vertical ozone change workshop, Geneva, 2011
• 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
Vertical ozone change workshop, Geneva, 2011
O3 profile retrieval algorithm
Vertical ozone change workshop, Geneva, 2011
• 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])
Vertical ozone change workshop, Geneva, 2011
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])
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
SCIAMACHY IUP O3 profile data set (version 2.0) was already used in 2 ozone trend studies
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
• Determination of “instrument drift” for each instrument :
“Instrumental drifts” established by Jones et al. [2009]
Vertical ozone change workshop, Geneva, 2011
Tangent height retrievals from SCIAMACHY limb-radiance profile observations in the UV
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
Monthly mean tropical (25° S – 25° N) TH offsets
Definition: TH offset = Level 1 TH – TRUE TH
Vertical ozone change workshop, Geneva, 2011
Monthly mean tropical L1 version 7.03 TH offsets
Trend: -54 m/year
Vertical ozone change workshop, Geneva, 2011
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)
Vertical ozone change workshop, Geneva, 2011
Current validation and trend study results
Vertical ozone change workshop, Geneva, 2011
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
Vertical ozone change workshop, Geneva, 2011
Mieruch et al., [2011]
Validation of SCIAMACHY vs. 2.1 ozone profiles
Vertical ozone change workshop, Geneva, 2011
• 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
Vertical ozone change workshop, Geneva, 2011
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.
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