Global Aerosol Climatology Using MODIS Observations

1. Towards a global aerosol climatology using MODIS observations Mean Terra AOT Oct 2000 -Oct 2005, courtesy GDAAC MOVAS web site Lorraine Remer, Yoram Kaufman, Didier Tanré Shana Mattoo, Richard Kleidman, Robert Levy Vanderlei Martins, Allen Chu, Charles Ichoku, Rong-Rong Li, Ilan Koren

2. February 2006 marks the 6th anniversary of our first look at MODIS aerosol products. What have we learned? - about the product - about global aerosols What do we still need to do? How do we use an aerosol climatology in the larger context of predicting climate change?

3. Offset over land Issues with aerosol models What have we learned -- about the product? Excellent validation, globally, with collocated data. (when both AERONET and MODIS report) Remer et al. (2005)

4. What have we learned -- about the ocean product? MOD - AER increases with cloud fraction But MODIS and AERONET AngExp track together Cirrus contamination over oceans contributes ~ 0.015 in AOT Kaufman et al. (2005)

5. What have we learned -- about the ocean product? Even without the benefits of collocation in time AOT is well-correlated with AERONET Kaufman et al. (2005)

6. What have we learned -- about the ocean product? Fine mode fraction also correlates well against two derivations from AERONET. Kleidman et al. (2005)

7. What have we learned -- about the ocean product? N=486 Terra’s and Aqua’s estimate of global AOT agree to better than 1% Remer, Kaufman, Kleidman

8. What have we learned -- about the ocean product? • POLDER/ADEOS-2 and MODIS/TERRA comparison • Equator Crossing Time = +/- 5mns apart between both instruments (10 days every month). • 30 coincident orbits (40 000 points) from May to October 2003. • Representative of typical geographical zones. • POLDER resolution = 20km2 ; MODIS resolution = 10km2.

9. MODIS vs. POLDER Coarse mode, non-Spherical, >70% Fine mode >70% Coarse mode, Spherical, >70% OVER OCEAN Gerard et al. 2005

10. What have we learned -- about the ocean product? • excellent validation of the inversion • -beginning to validate the product (aot and size) • -0.015 of the global aot over ocean is cirrus • -other cloud contamination is less obvious • -excellent agreement between Terra and Aqua (1%) • -excellent agreement between MODIS and POLDER • for spherical particles and less so for non-spherical

11. What have we learned -- about global aerosols? AOT 90% Ang mean FF 33% 10% Kleidman,Kaufman,Remer

12. What have we learned about global aerosols?

13. What have we learned about global aerosols?

14. What do we still need to do? LAND • new inversion scheme for better fine mode weighting • - new aerosol models and distribution (Dubovik 2002) • - new land surface parameterization (MVI and geometry) • - allowing negative retrievals

15. Elimination of Snow Contamination Li et al. (2005)

16. What do we still need to do?

17. What do we still need to do? Testbed =100 images, several days Golden=1 complete day (November) We intend to be ready with a final new algorithm within weeks. Then we need to negotiate intercepting the Collection 005 reprocessing.

18. How do we use the product? Using MODIS retrievals consistently as input to a RT model, we can accurately estimate aerosol direct radiative effect. Ocean DRE ~ -5.0 to -5.5 Wm-2 Remer and Kaufman (2006)

19. In just the past6 weeks, there have been5 paperseither just published or just accepted that use MODIS aerosol products to make estimates of the aerosol direct radiative effect or forcing on climate. Bellouin et al., in Nature Kaufman et al., in GRL Chung, Ramanathan et al., in JGR Yu et al., in ACP Remer and Kaufman, in ACP Atmospheric physics:Reflections on aerosol cooling p1091 of the NY Times “By changing the composition of Earth's atmosphere, human activity has both a warming and a cooling effect on the planet. According to new calculations, that latter influence is large, but it is likely to be declining.” Jim Coakley