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

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?

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

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

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)

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

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

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

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

What have we learned -- about the ocean product? -excellent validation of the inversion -beginning to validate the product (aot and size) 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

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

What have we learned about global aerosols?

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

Elimination of Snow Contamination Li et al. (2005)

What do we still need to do?

We intend to be ready with a final new algorithm within weeks. Then we need to negotiate intercepting the Collection 005 reprocessing. OldNew Testbed mean AOT Testbed negative07.5% Testbed x < % Golden mean AOT Golden negative022% Golden x < % Testbed =100 images, several days Golden=1 complete day (November)

How do we use the product? Remer and Kaufman (2006) 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

In just the past 6 weeks, there have been 5 papers either 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