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Validation of SCIAMACHY total ozone : ESA/DLR V5(W) and IUP WFDOAS V2(W)

Validation of SCIAMACHY total ozone : ESA/DLR V5(W) and IUP WFDOAS V2(W) . M. Weber, S. Dikty , J. P.Burrows , M. Coldewey-Egbers (1) , V. E. Fioletov (2) , S. M. Frith (3) , and D . Loyola (1) Contact : weber@uni-bremen.de DLR Oberpfaffenhofen Environment Canada NASA GSFC.

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Validation of SCIAMACHY total ozone : ESA/DLR V5(W) and IUP WFDOAS V2(W)

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  1. Validation of SCIAMACHY total ozone: ESA/DLR V5(W) and IUP WFDOAS V2(W) M. Weber, S. Dikty, J. P.Burrows, M. Coldewey-Egbers(1), V. E. Fioletov(2), S. M. Frith(3), and D. Loyola(1) Contact: weber@uni-bremen.de DLR Oberpfaffenhofen Environment Canada NASA GSFC SQWG Meeting, Bremen, Germany, 13-14 June 2013

  2. The datasets • ESA/DLR V5(W) • WFDOAS V2m(W) • with V7 L1 m-factor • WFDOAS V2(W) • without V7 L1 m-factor

  3. Correlativedatasets • WOUDC database (brewer/dobson/filter) • monthlymean zonal meandata (Fioletov et al. 2002) • Daily stationaverages (collocateddata) • SBUV mergeddata V8.6 • Monthlymean zonal meandata(Frith et al., 2012)

  4. Bias anddriftsof SCIA WFDOAS wrt GOME Drift (%/decade) Bias (% in 2002) w/o m-factors with m-factors

  5. Bias anddriftsof SCIA WFDOAS wrt GOME • GOME stableover a 16 yearperiod • m-factors (Bramstedt et al., 2009 mainlyreducesthedriftsat lowlatitudes, littlechangesabove50° • however, thedriftandbiaspatternlooks a bitmorecomplicated (e.g. someseasonaleffects) Drift (%/decade) Bias (% in 2002) with m-factors

  6. Zonal meancomparisonswith WOUDC • ESA/DLR higherthan WFDOAS (~1.5%), but both in verygoodagreementwith WOUDC (within ~1-2%, ~3-6 DU) • Small (negative) drift evident in ESA/DLR and WFDOAS with m-factorwrtto WOUDC • nosystematicdriftsbetween ESA andWFDm

  7. Zonal meancomparisonswithSBUV V8.6 • Verygoodagreementwith SBUV mergedforboth WFD V2m and ESA V5 (within 2%) • at polar latitudes (high SZA) negative biases in ESA/DLR • gradient in thebiasbetween SCIA and SBUV fromtropicsto high latitudes (biasdecreases) • weak positive driftwith time in thetropics

  8. Collocationwithgrounddata • Collocationcriteria: • 300 km • distanceweighted SCIA averages (withincollocationradius) • Separate comparisonwithdobsonsandbrewers • Seasonalcycle in differencesto Dobson generally larger thantobrewers • constantT in groundretrievals • temperaturesensitivitylower in brewers WFD(m) WFD ESA/DLR Example: comparisonwith Brewer atHohenpeissenberg, Germany (47°N)

  9. Station-by-station comparison • x WFDm: -0.7% WFDm: 0% ESA: +0.5% ESA: +1.0%

  10. Dependenceby SZA WFDm-dobson WFDm-brewer • x ESA-brewer ESA-dobson • Little SZA dependence • SZA dependence in Dobson comparisonrelatedtoseasonalvariations (T issues)

  11. Combinedozoneand SZA dependency: ESA V5 • Low illuminationconditions: high ozoneand/or high SZA: • Bias togroundincreases (straylightissueswithbothgroundandsatellitedata) • Special conditions: ozone hole conditions (verylowozone): • Grounddatatendtounderestimatebyupto 4% (Bernhard et al., 2005)

  12. Combinedozoneand SZA dependency: WFDOAS V2 • Low illuminationconditions: high ozoneand high SZA • Specualconditions: ozone hole conditions (verylowozone

  13. Summary & Conclusion • Verygoodagreementbetween SCIAMACHY (ESA & IUP) and WOUDC & SBUV merged (mostlywithin 1%) • Someissueswith ESA/DLR at polar latitudes (lowbias) • Small differences in biasandseasonalpatterns (ESA/DLR, WFDOAS) in differencesto SBUV and WOUDC aretheresultofslightlydifferingsettings (different scalingsof Bogumil cross-sections, choiceofozoneprofileclimatology, different algorithmapproach, and so on) • The m-factorapproachfor L1 V7 successfullyremovesthedrift in SCIAMACHY total ozonedata (still someissues in thefirstyearofthedatarecord) • WFDOAS V2 with m-factoragreesbetterthan ESA V5, withthenew GTO mergeddataset (based upon GODFIT, Lerot et al. 2014, Chiou et al., 2013) • RECOMMENDATION: GODFIT asthefuture ESA V6 will be an improvementover SGP 5 (see also Lerot et al. 2014)

  14. APPENDIX

  15. DOAS total ozoneretrievalandozonetemperature Weighting function DOAS • DOAS satelliteretrievals (OMI, GOMEs, SCIAMACHY) • 325-335 nm (WFDOAS: 326.6-334.5 nm) • U Bremen retrieval: Weightingfunction DOAS (Coldewey-Egbers et al., 2005, Weber et al., 2005, Lee et al., 2008) • scalartemperatureshift in the a-priori temperatureprofile • effectiveozonetemperature TO3 • Both total ozoneandtemperaturedependon ozonecross-sectionchoice Coldewey-Egbers et al., 2005 Radiation transfer model retrieved total ozone retrieved ozonetemperature

  16. Ozoneandtemperaturetermsin WFDOAS equation GOME • Anti-correlationbetweenozoneandozonetemperatureterm • Depending on fittingwindowsizeandpositioncorrelationrangesbetweenr = -0.4 and -0.6 Coldewey-Egbers et al., 2005

  17. WFDOAS total ozonedatasets& cross-sectionused • WFDOAS appliedto GOME (1995-2011), SCIAMACHY (2002-2012), and GOME-2 (since 2006) • GOME1/ERS : Burrows et al. 1999 (GOME FM), shift: +0.017 nm • SCIAMACHY/ENVISAT: Bogumil et al., 2003 (SCIA FM), scaled 5.3%, shift: +0.008 nm • GOME2/METOP A: Burrows et al., 1999, convolved, shift: +0.017nm • agreementtowithin 1% with WOUDC breweranddobsons • Nevertheless: useof a singlecross-sectiondatafor all instrumentsareneededtobetterunderstandcalibrationdifferencesbetweeninstruments merged WFDOASdatarecord (Weber et al. 2011, 2012 )

  18. Satellitevsground

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