Lorraine Remer, Yoram Kaufman, Didier Tanr

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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
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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?
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What have we learned -- about the product?
Excellent validation, globally, with collocated
data.
(when both AERONET and MODIS report)
Remer et al. (2005)
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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)
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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)
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What have we learned -- about the ocean product?
Fine mode fraction also correlates well
against two derivations from AERONET.
Kleidman et al. (2005)
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What have we learned -- about the ocean product?
N486
Terras and Aquas estimate of global AOT agree
to better than 1
Remer, Kaufman, Kleidman
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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.

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MODIS vs. POLDER
Coarse mode, non-Spherical, gt70
Fine mode gt70
Coarse mode, Spherical, gt70
OVER OCEAN Gerard et al. 2005
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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

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

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Elimination of Snow Contamination
Li et al. (2005)
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What do we still need to do?
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What do we still need to do?
Old New
Testbed mean AOT 0.27 0.19
Testbed negative 0 7.5
Testbed x lt -0.05 0 2
Golden mean AOT 0.16 0.07
Golden negative 0 22
Golden x lt -0.05 0 11
Testbed 100 images, several days Golden1
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.
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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)
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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