1. Braak et al., OMI Science Team Meeting 6 June 2007 OMI Multiwavelength Aerosol Product Validation Status Remco Braak, Ben Veihelmann, Pepijn Veefkind

2. Braak et al., OMI Science Team Meeting 6 June 2007 Aerosols are different from molecules! Aerosols vary wildly: Size (5 parameters) Composition (2 parameters) Veihelmann: 2-4 pieces of information in OMI -> underdetermined Every ozone molecule is the same

3. Braak et al., OMI Science Team Meeting 6 June 2007 OMI Multiwavelength Aerosol Product (OMAERO) 50 aerosol models (weakly absorbing, biomass burning, desert dust) Aerosol optical thickness AOT from fit to OMI spectrum (up to 19 ’s) Best-fit model ‘wins’ – further constrained by aerosol climatology NEW: Collection 3 reprocessed up to September 2006  Provisionally released Following presents first comparisons of OMAERO collection 3 with other data sets

4. Braak et al., OMI Science Team Meeting 6 June 2007 OMAERO Data Example – Namibia MODIS-Aqua, 10 July, 2005 OMAERO AOT at 483.5 nm

5. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET AErosol RObotic NETwork -CIMEL Sunphotometers -About 120 stations active worldwide -AOT (340-1020 nm) every 15 minutes

6. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET – Comparison Procedure OMAERO: Pixel 13 x 24 km 2 minimum Alta Floresta AERONET: Much more localized More honest comparison: OMAERO 50-km-radius average AERONET 1-hour average

7. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 Heligoland – Best result!

8. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 Ilorin – notable for three aerosol types

9. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 Birdsville – surface albedo problems over deserts

10. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 MD Science Center – good correlation, but OMAERO overestimates

11. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 Dhadnah – bias also for desert dust regions

12. Braak et al., OMI Science Team Meeting 6 June 2007 AERONET Comparison Examples – 2005 Alta Floresta – bias also for biomass burning regions

13. Braak et al., OMI Science Team Meeting 6 June 2007 MODIS Moderate-Resolution Imaging Spectroradiometer ~15 minutes ahead of OMI in the A-Train Swath slightly narrower than OMI’s 10 x 10 kilometer resolution

14. Braak et al., OMI Science Team Meeting 6 June 2007 MODIS – Comparison Procedure Intersecting MODIS pixels sought for each OMAERO pixel MODIS AOT* averaged using overlap areas (sq. deg.) as weights *MYD04 collection 5

15. Braak et al., OMI Science Team Meeting 6 June 2007 MODIS Examples – August 2005 Sahara (desert dust) r = 0.86 High correlation (Only ocean pixels – MODIS does not retrieve over desert)

16. Braak et al., OMI Science Team Meeting 6 June 2007 MODIS Examples – August 2005 East US (weakly absorbing) r = 0.59 Much poorer correlation OMI overestimates

17. Braak et al., OMI Science Team Meeting 6 June 2007 MODIS Examples – August 2005 Amazon (weakly abs. + biomass b.) Biomass burning Weakly absorbing r = 0.93 BB: r = 0.93 WA: r = 0.74 Type-dependent correlation

18. Braak et al., OMI Science Team Meeting 6 June 2007 Other OMAERO Validation Tim Vlemmix (KNMI) – GLOBE John Livingston (NASA-Ames) – Aircraft measurements Virginie Buchard (LOA) – Photometer Villeneuve d’Ascq Alex Kokhanovsky (Uni Bremen) – MISR/MODIS-Terra/AATSR Lyana Curier (TNO-FEL) – MODIS/AERONET

19. Braak et al., OMI Science Team Meeting 6 June 2007 Alex Kokhanovsky Good correlation (despite time and location differences) AATSR overestimates – fixed with higher single-scattering albedo Instrument intercomparison over Germany, 13 October 2005

20. Braak et al., OMI Science Team Meeting 6 June 2007 Lyana Curier Higher correlation and closer to 1-1 over sea than over land Comparison OMI-MODIS over Western Europe, June 2005 MODIS AOT at 470 nm OMI AOT at 471 nm OceanLand

21. Braak et al., OMI Science Team Meeting 6 June 2007 Conclusions Appreciable correlation between OMAERO and AERONET, and between OMAERO and other satellite instruments OMAERO product is used outside OMI team Outlook Investigate overestimation  Possible candidates: type misattribution, clouds, aerosol altitude Apply more quality constraints Application of OMI’s own surface albedo climatology Use additional correlative data: CALIPSO, PARASOL

22. Braak et al., OMI Science Team Meeting 6 June 2007 Availability OMAERO data are provisionally released  send an e-mail to Ben Veihelmann ( veihelma@knmi.nl ). Expected public release: summer 2007