1. Vertical ozone change workshop, Geneva, 2011 SCIAMACHY 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 ozone Geneva, January 25 – 27, 2011

2. 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

3. 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

4. Vertical ozone change workshop, Geneva, 2011 O 3 profile retrieval algorithm

5. Vertical ozone change workshop, Geneva, 2011 Simultaneous retrieval in Hartley, Huggins and Chappuis bands (Currentversion 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 O 3 absorption cross section Burrows et al. [1999])

6. Vertical ozone change workshop, Geneva, 2011 Step 1: Tangent height Normalization Methodology Step 2: Form Chappuis-triplet (Flittner, 2000; von Savigny, 2002) Wavelengths (nm)264267.5273.5283286288290305525602675 TH low (km)52 45 35999 TH ref (km)71 6865 615541 Then construct retrieval vector: I: Limb radiance TH: tangent height TH ref :reference tangent height k: wavelength index (k  [1,11])

7. Vertical ozone change workshop, Geneva, 2011 FeatureAdditional remarks Retrieved quantityO 3 concentration Altitude gridRegular 1 km grid (10 – 80 km) Inversion schemeIterative Gauss-NewtonWeak statistical contraint and smoothness constraint Radiative Transfer ModelSCIATRAN version 3.1 Weighting function calculation Analytically in single-scattering mode Vertical resolutionAbout 4 km between 15 and 65 km altitude Averaging kernels for every retrieved profiles available Level 1 data usedVersion 6.03 or higherIncluding AUX_FRA platform attitude correction files as well as SCIAMACHY extra misalignment correction Background atmosphere6-hourly pressure & temperature data from ECMWF analyses Stratospheric 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 dataMatthews [1984] data base O 3 X-sectionsBogumil Version 2.0SCIAMACHY FM X-sections Pointing correctionNo additional pointing correction Cloud flaggingTropospheric, stratospheric and mesospheric clouds are detected Cloud flags provided in O 3 Level 2 data Features of version 2.3 O 3 profiles

8. 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 retrieval But:Basic sensitivities are similar for SCIAMACHY Comprehensive sensitivity analysis for extended SCIAMACHY retrieval currently underway within ESA-CCI project

9. 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 O 3 profile retrievals

10. Vertical ozone change workshop, Geneva, 2011 SCIAMACHY IUP O 3 profile data set (version 2.0) was already used in 2 ozone trend studies

11. 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 O 3

12. 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 O 3

13. Vertical ozone change workshop, Geneva, 2011 Determination of “instrument drift” for each instrument : “Instrumental drifts” established by Jones et al. [2009]

14. Vertical ozone change workshop, Geneva, 2011 Tangent height retrievals from SCIAMACHY limb- radiance profile observations in the UV

15. 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 O 3. Technical features of TRUE (vs 1.8): IUP dynamical O 3 climatology [Lamsal et al., 2003] together with EP-TOMS and OMI Total ozone column (TOC) data for each day and location. Climatological O 3 profiles scaled to TOC value. Use of ECMWF background atmosphere for date, time and coordinates of every SCIAMACHY limb state analyzed

16. Vertical ozone change workshop, Geneva, 2011 Monthly mean tropical (25° S – 25° N) TH offsets Definition: TH offset = Level 1 TH – TRUE TH

17. Vertical ozone change workshop, Geneva, 2011 Monthly mean tropical L1 version 7.03 TH offsets Trend:  -54 m/year

18. 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 (Level 1) – TH (retrieved) [km] Year Data provided by Klaus Bramstedt (IUP Bremen)

19. Vertical ozone change workshop, Geneva, 2011 Current validation and trend study results

20. 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 submitted to JGR [2011] Version 6.2 Version 2.2 Version 1.07 Thermal IR Version 19

21. Vertical ozone change workshop, Geneva, 2011 Mieruch et al., [2011] Validation of SCIAMACHY vs. 2.1 ozone profiles

22. 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 Mieruch et al., [2011] No statistically significant trends detected for 2004 – 2008 ! Trends in % / year

23. Vertical ozone change workshop, Geneva, 2011 Conclusions IUP SCIAMACHY O 3 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 ESA’s Ozone-CCI Compilation of comprehensive error budget for IUP Bremen SCIAMACHY limb ozone profile data set ongoing within ESA’s Ozone-CCI project Comparisons with independent satellite data sets and trend analyses indicate anomalous trend in SCIAMACHY O 3 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.