global estimates of ambient fine particulate matter...
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Global Estimates of Ambient Fine Particulate Matter Concentrations from Satellite-Based Aerosol Optical Depth: Development and Application
Aaron van Donkelaar1, Randall V. Martin1,2, Michael Brauer3, Ralph Kahn4, Robert Levy4, Carolyn Verduzco1, and Paul J. Villeneuve5,6
van Donkelaar et al., Environmental Health Perspectives118(6), 2010
This work was supported by Health Canada.
SummaryWe develop a 0.1º x 0.1º global climatology of PM2.5 by combining satellite retrievals from the MODIS and MISR instruments with modelled aerosol properties from 2001-2006. We find significant agreement with surface measurements (r=0.77) and estimate that 80% of the world’s population exposure to PM2.5 exceeds Air Quality Guideline of 10 μg/m3.
Combining AOD for improved accuracy and coverage
Aerosol Optical Depth (AOD) is a measure of light extinction through the atmospheric column due to the presence of aerosol. We use the MODIS and MISR instruments onboard the Terra satellite to obtain global AOD coverage. We compare satellite and AERONET AOD within surface reflectance-based land types and remove satellite AOD over surfaces with error exceeding 0.1 or 20%. This filtration significantly improves agreement with PM2.5.
Relating AOD to PM2.5
The relationship between AOD and ground level PM2.5depends on many factors, and is predominately affected by the aerosol’s vertical structure and composition. We use a chemical transport model (GEOS-Chem) to relate AOD to PM2.5.
1,0570.771.066Satellite-derived PM2.5
1,0570.610.017Combined AOD1,2360.440.015Average AOD3530.390.010MISR AOD
1,2180.390.020MODIS AODnrSlopeRetrieval
Com
bine
dM
OD
ISM
ISR
AO
D [
unitl
ess]
0.3
0.25
0.2
0.15
0.1
0.05
0.0Table 1: Comparison of coincidently sampled 6-year
mean measurements of daily 24-hr average PM2.5 with AOD and satellite-derived PM2.5
PM2.5 / AOD [μg/m3]
Comparing satellite-derived PM2.5 with surface
measurementsApplication of simulated AOD-PM2.5 factors to the filtered AOD retrievals yields significant agreement with coincidently sampled ground measurements over North America (r=0.77). Lack of data prohibits a global coincident comparison, but a non-coincident comparison shows similar agreement (r=0.83).
Assessing ambient PM2.5 exposureWe combine our satellite-derived PM2.5 with the global population distribution to estimate ambient exposure. 80% of the world’s population lives in excess of the World Health Organization’s Air Quality Guideline (WHO AQG) of 10 μg/m3. 50% of the east Asian population exceeds the WHO AQG-1 of 35 μg/m3.
1Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada2Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA
3School of Environmental Health, University of British Columbia, British Columbia, Canada
4NASA Goddard Space Flight Center, Greenbelt, Maryland, USA5Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
6Population Studies Division, Health Canada, Ottawa, Ontario, Canada
Satellite-Derived PM2.5 [μg/m3]0 5 10 15 20 50 80
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Pop
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5 10 15 25 35 50 100PM2.5 Exposure [μg/m3]
AQG IT-3 IT-2 IT-1WHO Air Quality Guideline and Interim Targets
Population Density Surface Elevation
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Sat
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181614121086420
20 40 60 80 100 120 140
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IntroductionLong-term exposure to fine aerosol with aerodynamic diameter < 2.5 μm (PM2.5) is associated with adverse human health impacts, yet monitoring of this pollutant is sparse in many regions of the world. Satellite-derived estimates of PM2.5 offer a valuable tool with which to assess the impact of these aerosol.