Recalibrated Ozone Profiles from GOME-UV/Vis Nadir spectra Silvia Tellmann, Mark Weber, Vladimir Rozanov, and John Burrows Institute of Environmental Physics/ Institute of Remote Sensing University of Bremen ERS-ENVISAT Symposium, Salzburg, 6-10 Sep 2004

O3 nadir profiling in Bremen Calibration Problems in FURM V5 Improved calibration correction low latitude approach global approach Improved tropospheric retrieval Conclusion Overview

GOME O3 profile retrieval in Bremen Full Retrieval Method (FURM):  Optimal estimation and Kozlov information matrix approach & validation with ozone sonde data R. Hoogen, V.V. Rozanov, J.P. Burrows, Ozone Profiles from GOME Satellite Data: Algorithm Description and First Validation, J. Geophys. Res., 104, , R. Hoogen, V.V. Rozanov, K. Bramstedt, K.-U. Eichmann, M. Weber, and J.P. Burrows, Ozone profiles from GOME satellite data-I: Comparison with ozonesonde measurements, Physics and Chemistry of the Earth 24, ,  Extensive validation of Version 5 with lidar and satellite data K. Bramstedt, K.-U. Eichmann, M. Weber, V. Rozanov, and J. P. Burrows, GOME ozone profiles: A global validation with HALOE measurements, Adv. Space Res. 29, , K. Bramstedt, J. Gleason, D. Loyola, W. Thomas, A. Bracher, M. Weber, and J. P. Burrows, Comparison of total ozone from the satellite instruments GOME and TOMS with measurements from the Dobson network , Atmospheric Chemistry and Physics 3, , G. Hansen, K. Bramstedt, V. Rozanov, M. Weber, and J.P. Burrows, Validation of GOME ozone profiles by means of the ALOMAR ozone lidar, Annales Geophysicae 21, , A. Bracher, M. Weber, K. Bramstedt, S. Tellmann, J. P. Burrows, Long-term global measurements of ozone profiles by GOME validated with SAGE II considering atmospheric dynamics, J. Geophys. Res., accepted, 2004.

GOMEO3 profile retrieval in Bremen (II)  Application in scientific studies: Arctic ozone depletion, international field campaigns (OFP, THESEO2000), ozone miniholes K.-U. Eichmann, K. Bramstedt, M. Weber, R. Hoogen, V.V. Rozanov, and J.P. Burrows, Structure of ozone mini-holes from GOME, European Symposium on Atmospheric Measurements from Space, Proc. ESAMS'99, ESA-WPP-161, , K.-U. Eichmann, K. Bramstedt, M. Weber, V.V. Rozanov, R. Hoogen and J.P. Burrows, O3 profiles from GOME satellite data - II: Observations in the Arctic spring 1997 and 1998, Physics and Chemistry of the Earth 24, , H. Bremer, M. von König, A. Kleinböhl, H. Küllmann, K. Künzi, K. Bramstedt, J. P. Burrows, K.- U. Eichmann, M. Weber, A. P. H. Goede, Ozone depletion observed by ASUR during the Arctic Winter 1999/2000, J. Geophys. Res. 107, 8277, doi: /2001JD000546, K.-U. Eichmann, M. Weber, K. Bramstedt, and J.P. Burrows, Ozone depletion in the NH winter/spring 1999/2000 as measured by GOME-ERS2, J. Geophys. Res. 107, 8280, doi: /2001JD001148, U. Klein, I. Wohltmann, K. Lindner, and K. F. Künzi, Ozone depletion and chlorine activation in the Arctic winter 1999/2000 observed in Ny-Ålesund, J. Geophys. Res., 107 (D20), 8288, doi: /2001JD000543,  Continued development: tropical retrieval (wavelength extension) and cloud/albedo effects, a-priori profile sensitivity S. Tellmann, S., V.V. Rozanov, M. Weber, and J.P. Burrows, Improvements in the tropical ozone profile retrieval from GOME UV/vis nadir spectra, Adv. Space Res. 34, , L. N. Lamsal, M. Weber, S. Tellmann, and J. P. Burrows, Ozone column classified climatology of ozone and temperature profiles based on ozonesonde and satellite data, J. Geophys. Res., accepted, 2004.

calculate ozone on several altitude levels  large number of parameters: n  70 Develop the profile in a sum of eigenfunctions with proper truncation  n  10 Kozlov-Information-matrix-method combined with optimal estimation: FURM inversion scheme O3-eigenvectors in altitude range altitude [km] O3-EV [-] O3-eigenvectors in wavelength range O3-EV [-] Wavelength [nm]

Radiometric calibration problems ratio of GOME solar spectra direct after launch and 5 years later degradation dichroic mirror Ratio [-] etalon Wavelength [nm] outgassing (mainly optical coatings e. g. dichroic mirror) change optical features etalon structures: contamination layers on cooled detectors (ice) varies in time  spectral modulation UV degradation of the instrument: scan mirror is exposed to UV- radiation polarization degradation

FURM V5 empirical calibration wavelength range: 290 – 340 nm broadband calibration correction to allow for UVdegradation  Chebychev Polynomials Channel 1 polynomials [-] wavelength [nm] Chebychev Polynomials Deviations between model and measurement residual [-] wavelength [nm] differential corrections: NOT applied !!!!  V5 restricted to wavelengths

Shortcomings in FURM V5 lack of information in upper stratosphere (above km) problems in tropics where ozone maximum is shifted to higher altitudes  wavelengths below 290 nm needed to enhance stratospheric information content  Chebyshev polynomials inadequate at short wavelengths Sensitive to measurement measurement sensitivity Altitude [km] Sum of rows AK-Matrix [-] ozone profiles in tropics Altitude [km] FURM SAGEII Climatology O3-concentration

Tropical calibration correction Diff. error Differential sunnormalized radiance GOME Model wavelength [nm] y_meas [-] wavelength [nm] residual & fit of diff. error GOME - Model 5D-4 3D-4 1D-4 -1D-4 5D-4 3D-4 1D-4 -1D-4 y_meas – y_model [-]  large differential structures below 290 nm  strong filling-in of Fraunhofer lines New corrections by differential fit:  Fit addition error term: a ~1/ irradiance  1/irr & polynomial fit before ozone retrieval (prefit in Ch. 1)

High latitude calibration correction  Ozone maximum in middle and high latitudes shifted to lower altitudes and longer wavelengths  low differential structure of ozone absorption  strong correlations between broadband calibration  corrections and atmospheric parameter  change of broadband calibration correction required below 300 nm  statistical investigation of residuals Mean residuals in comparison with HALOE Residual [-] 285 wavelength [nm]

Results from 1997 tropics Rel. Deviations Old Rel. Deviations New Relative deviations between standard version/new version and independent measurement from SAGE II (Stratospheric Aerosol and Gas Experiment II) Old New 2(SAGE-GOME)/(SAGE+GOME) 50 Altitude [km] Comparison of O3 [ppm] SAGE/FURM altitude [km] latitude [deg] old results new results

Results from 2003 New Results No of Pixel old results No of Pixel Altitude [km] Relative deviations between SAGE II and FURM Comparison of O3 [ppm] SAGE/FURM altitude [km] (SAGE-GOME)/(SAGE+GOME) Old New new results latitude [deg]

Tropospheric retrieval  retrieved tropospheric ozone always quite near to climatological values  averaging kernels (AKs) indicate where information in retrieved height level comes from Aks for retrieval levels in troposphere Averaging Kernels [-] altitude [km] O3 Conc FURM Sonde Climatology altitude [km] Ozone Profile Hohenpeissenberg

Tropospherical investigations Profile fit: spectral window too large to make accurate tropospheric ozone fit Use just channel 2 to improve tropospheric column fit Two step retrieval: 1.Common ozone profile fit to get information about stratospheric constituents. 2. Use fitted profile and investigate residual in channel 2 (~ nm)  troposphere here defined up to ECMWF thermal tropopause  Make new diff. fit of tropospherical ozone column, temperature and Ring (inelastic scattering)

Sensitivity in Channel 2 Residual & Fit Residual Fit all param. Trop. Col. New col. Old col. Temp. Fit Ring Fit Ring WF fit [-] T WF fit [-] O3 WF fit [-] Residual [-] wavelength [nm]

Tropospherical Column Results Relative Deviations between O3–Sonde and climatology as well as FURM Hohenpeissenberg 1997 Rel. deviations Sonde-Climatology [-] Rel. deviations Sonde-FURM [-] troposph. columns from profile retrieval troposph. columns from differential fit in channel 2 regression line for profile fit regression line for step 2 differential fit in channel 2 + in most cases improvements for very small differences to climatological value instabilities in differential fit (noise)

Conclusions  Stratospheric information content can be enhanced by combined calibration concept in short wavelength region using differential „dark current“ approach for tropics/southern anomaly residual fit for middle and high latitudes.  Tropospheric retrieval based upon two step approach accurate stratospheric ozone fit accurate fit of Ring & atm. Parameters realistic climatological ozone profile form  Inclusion of new ozone a-priori climatology (Lamsal et al. 2004)  Reprocessing of GOME in preparation (funding?)  First application to SCIAMACHY (Version 5)

A-priori profile sensitivity  IUP climatology (Lamsal et al., JGR, 2004)  F&K (Fortuin and Kelder, JGR, 1998)  Improvement in the lowermost stratosphere with IUP climatology  see also talk by Lamsal et al. (Abstract 353) for details on IUP O3 climatology 23 August 2002 Hohenpeissenberg 1997

SCIAMACHY nadir application  limb retrieval V1.6 (Savigny et al., JAS, 2004)  FURM nadir retrieval Version 5  there are still outstanding issues regarding calibration  Visit poster by Bramstedt et al. (3P08-6) for more details 23 August 2002

The Global Ozone Monitoring Experiment Launched in april 1995 on ERS-2 Nadir viewing grating spectrometer Measures backscattered Rad and direct radiance Irr between 240 – 790 nm. Spectral resolution ~ nm Measurand: Sunnnormalized Radiance Rad Irr

Basics of Inversion Theory Basic Idea: use forward model and minimize differences between measurement and model Inversion Ozone Profile Ozone Concentration wavelength [nm] Forward Model altitude [km] Sunnormalized Radiance y_meas [-] Model O profile true atmospheric O profile x 3 3

Problems of Inversion Theory 1.Nonlinear dependencies: linearization 2.Contradictory solutions: calculate ‘‘best estimate‘‘ 3. Correlations: less independent information than wanted parameters use additional information from climatology to regularize the retrieval Optimal Estimation Method Measurement - & Clim.-Error-Correlation Matrix