Global Climatology of Fine Particulate Matter Concentrations Estimated from Remote-Sensed Aerosol Optical Depth

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Global Climatology of Fine Particulate Matter
Concentrations Estimated from Remote-Sensed
Aerosol Optical Depth
Aaron van Donkelaar1, Randall Martin1,2, Ralph
Kahn3 and Robert Levy3 AGU Fall Meeting December
13-18, 2009 1Dalhousie University
2Harvard-Smithsonian 3NASA Goddard
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Approach
We relate satellite-based measurements of aerosol
optical depth to PM2.5 using a global chemical
transport model
Following Liu et al., 2004
Estimated PM2.5 ? t
Combined MODIS/MISR Aerosol Optical Depth
GEOS-Chem
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MODIS and MISR t
Mean t 2001-2006 at 0.1º x 0.1º

• MODIS t
• 1-2 days for global coverage
• Requires assumptions about surface reflectivity

MODIS
r 0.40 vs. in-situ PM2.5

• MISR t
• 6-9 days for global coverage
• Simultaneous surface reflectance and aerosol
  retrieval

MISR
r 0.54 vs. in-situ PM2.5
0 0.1 0.2 0.3
t unitless
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Agreement varies with surface type
July
MODIS
MISR
9 surface types, defined by monthly mean surface
albedo ratios, evaluation against AERONET AOD
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Combining MODIS and MISR improves agreement
0.3 0.25 0.2 0.15 0.1 0.05 0
t unitless
Combined MODIS/MISR r 0.63 (vs. in-situ PM2.5)
MODIS r 0.40 (vs. in-situ PM2.5)
MISR r 0.54 (vs. in-situ PM2.5)
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Global CTMs can directly relate PM2.5 to t
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Significant agreement with coincident ground
measurements over NA
r
MODIS t 0.40
MISR t 0.54
Combined t 0.63
Combined PM2.5 0.78
Annual Mean PM2.5 µg/m3 (2001-2006)
Satellite Derived
Satellite-Derived µg/m3
In-situ
In-situ PM2.5 µg/m3
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Method is globally applicable

• Annual mean measurements
• Outside Canada/US
• 244 sites (84 non-EU)

• r 0.83 (0.91)
• slope 0.86 (0.84)
• bias 1.15 (-2.52) µg/m3

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WHO Guideline
High global PM2.5 exposure
AQG IT-3 IT-2 IT-1
100 90 80 70 60 50 40 30 20 10 0

• Satellite-PM2.5 population map ? exposure
• 80 of world population exceeds WHO guideline of
  10 µg/m3
• 49 of eastern Asia exceeds 35 µg/m3

Population
5 10 15 25 35 50
100
PM2.5 Exposure µg/m3