1. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 A combined retrieval, modelling and assimilation approach to estimate tropospheric NO2 from OMI measurements Ruud Dirksen, Folkert Boersma 1, Henk Eskes, Ronald van der A, Pepijn Veefkind, Pieternel Levelt, Ellen Brinksma, Eric Bucsela 2, Ed Celarier 2, Jim Gleason 2 KNMI, the Netherlands 1 Harvard, USA 2 NASA, USA

2. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Eleven years of NO2 data GOME, 1996 - 2003 SCIAMACHY, 2003 - present KNMI - IASB retrieval OMI, 2004 - present KNMI - NASA retrieval Images and detailed data products, including averaging kernels and error estimates, available on the TEMIS and PROMOTE web sites www.temis.nl www.gse-promote.org

3. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 OMI instrument overview Nadir viewing imaging spectrometer Wide swath (2600km) & high spatial resolution (13x24/48 km2) => Daily global coverage 2D-CCD detectors: instantaneous recording of FOV and spectrum Spectral range 270-500nm (0.4 – 0.6nm resolution) Data products: O3 column & profile, NO2, aerosols, clouds, SO2, BrO, OClO, HCHO EOS-AURA platform, launched 15 July 2004 Sun-synchronous orbit, equator overpass time 13:40

4. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 There are two OMI products: 1. Operational product (NASA-KNMI) 2. Near-real time product (KNMI-NASA) To provide users with near-real time air pollution monitoring environmental agencies, air quality forecasters EU GEMS project: - NRT comparison OMI with regional AQ models over Europe To generate a long-term consistent dataset from GOME, SCIAMACHY, OMI, GOME-2 Near real time OMI data publicly available since October 2006 via www.temis.nl Boersma et al. Atmos.Chem.Phys. 7, 2103, 2007 OMI near-real time product: Purpose

5. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 NO2 retrieval developed at KNMI Combined retrieval- modelling- assimilation-approach Boersma et al. JGR, D04311, 2004

6. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 NO2 retrieval: error contributions Typical 30-50% error for individual pixels Boersma et al. JGR 2004

7. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Ingredient 1: Daily chemical forecast with OMI NO2 assimilation Large uncertainty on slant columns with estimated high tropospheric column

8. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Ingredient 2: Near-real time OMI tropospheric NO2 retrieval NASA/KNMI DOAS algorithm Processing time < 2 mins

9. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Reprocessing status L1b reprocessing of entire mission completed L2 reprocessing will commence within a few weeks DOMINO reprocessing follows immediately after completion of L2 reprocessing (~2 months) Changes No de-striping (optional - after the retrieval) HDF-EOS5 output format to be consistent with other OMI products

10. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Reprocessing changes Better handling of flagging in L2 algorithm (filtering of e.g. saturated pixels) less spurious pixels Annual mean solar irradiance spectrum => reduction of stripes, improved S/N Better dark current correction => reduction of stripes. Stripe at least factor 3 smaller

11. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Reprocessing changes v3 (2007 reprocessing) v2

12. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Reprocessing changes v3 with stripe filtering v3 (2007 reprocessing)

13. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 GOME NO2 intercomparison IPCC context Van Noije et al., ACP 2006 NO2 products: Univ. Bremen (A. Richter) Harvard, Dalhousie (R. Martin) IASB / KNMI

14. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 GOME NO2 intercomparison IUP BremenDalhousieKNMI/BIRA NsNs 425 – 455 nm425-450 nm426.3 – 451.3 nm N s,st Ref. sector scaled to SLIMCAT strat. Ref. SectorData-assimilation in TM4 Cloud fraction (albedo) FRESCO 0.2 cloud fraction; only cloud selection, no further correction GOMECAT (Kuruso)FRESCO (0.8) Cloud pressure Not usedGOMECATFRESCO Albedo GOME (Koelemeijer) TOMS/GOME (1  x1  ) Profile shape MOZART-2 run for 1997, monthly averages on 2.8 x 2.8 ° GEOS-CHEM TM4 (3  x2  ) Temperature correction No?Yes, ECMWF T- profiles

15. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Validation with surface measurements Schaub et al., ACP 6, 2006 Cloud free Cloudy Daniel Schaub, EMPA

16. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 SCIAMACHY vs. Chimère: yearly mean 2003 Blond et al., JGR 112, 2007

17. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 KNMI OMI near-real time NO2, 13-16 Oct 2005 SundaySaturday

18. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Chimere model @ OMI overpass time, 13-16 Oct 2005

19. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Tropospheric NO 2 by OMI, May 2006

20. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Recent results: Greek forest fires August 2007

21. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Mediterranean Apr 2006May 2006 Sep 2006Oct 2006

22. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 OMI - SCIAMACHY, May & July 2006 Differences due to diurnal variation in emission Boersma et al. submitted to JGR Boersma et al., submitted to JGR

23. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Dandelions, OMI L2 and OMI NRT

24. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Dandelions, OMI L2 and OMI NRT

25. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 GOME / SCIA / OMI experience retrieval improvements should focus on cloud/aerosol treatment, surface albedo, stratospheric background, profile shape Comparison algorithms: KNMI-NASA-IUP-BIRA-Dal-UHei 2007 reprocessing major improvement SCIA + OMI : morning vs afternoon Comparison with regional-scale models to exploit resolution Future: Use of NRT-OMI (GOME-2) for air-quality applications Conclusions

26. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 1. Find window with smallest variation in initial columns 2. Compute mean column vs. across track viewing angle 3. FFT analysis to smooth Stripe correction

27. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 SCIAMACHY - OMI, October 2004

28. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 SCIAMACHY, October 2004

29. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 OMI, October 2004

30. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 SCIAMACHY - OMI, October 2004

31. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Trend over China GOME, 1997SCIA, 2004 R.J. van der A et al., JGR 111, 2006

32. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Van der A et al., 2006 Trend in NO2 column over China

33. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Van der A et al., 2006 Trend NO2 concentration worldwide

34. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Seasonal dependence, GOME en SCIAMACHY

35. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Seasonal dependence, TM4 model

36. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 Source attribution

37. Henk Eskes, NO2 workshop KNMI, 10 Sep 2007 OMI - SCIAMACHY, average