1. Satellite Remote Sensing of Global Air Pollution
Randall Martin, Dalhousie and Harvard-Smithsonian
Aaron van Donkelaar, Dalhousie University
Lok Lamsal, Dalhousie University  NASA Goddard
with contributions from
Michael Brauer, UBC
Rob Levy, Ralph Kahn, NASA
Symposium on Air Quality and Health in Atlantic Canada: New Directions and Opportunities
16 February 2011

2. Locations of Publicly-Available Long-Term PM2.5 Monitoring Sites
Large Regions Have Insufficient Measurements for Air Pollution Exposure Assessment
Locations of Publicly-Available Long-Term PM2.5 Monitoring Sites
Aaron van Donkelaar

3. Aerosol Remote Sensing: Analogy with Visibility Effects of Aerosol Loading
Waterton Lakes/Glacier National Park
Pollution haze over East Coast
7.6 ug m-3
22 ug m-3

4. Combined Aerosol Optical Depth (AOD) from MODIS and MISR Instruments for 2001-2006
MODIS/MISR
r = 0.63 (vs. in-situ PM2.5)
van Donkelaar et al., EHP, 2010

5. Chemical Transport Model (GEOS-Chem) Simulation of Aerosol Optical Depth
Aaron van Donkelaar

6. Ground-level “Dry” PM2.5 = η · AOD
η affected by vertical structure, aerosol properties, relative humidity
Obtain η from aerosol-oxidant model (GEOS-Chem) sampled coincidently with satellite obs
GEOS-Chem Simulation of η for
van Donkelaar et al., EHP, 2010

7. Significant Agreement with Coincident In situ Measurements
MODIS τ
0.40
MISR τ
0.54
Combined τ
0.63
Combined PM2.5
0.77
Annual Mean PM2.5 [μg/m3] ( )
Satellite
Derived
Satellite-Derived [μg/m3]
In-situ
In-situ PM2.5 [μg/m3]
van Donkelaar et al., EHP, 2010

8. Global Climatology (2001-2006) of PM2.5
Evaluation with measurements outside Canada/US
Number sites
Correlation
Slope
Bias (ug/m3)
Including Europe
244
0.83
0.86
1.15
Excluding Europe 84
0.91
-2.5
Better than in situ vs model (GEOS-Chem): r= , slope = 0.63 – 0.71
van Donkelaar et al., EHP, 2010

9. US standard: 15 ug/m3 in annual mean
van Donkelaar et al., EHP, 2010

10. van Donkelaar et al., EHP, 2010

11. Long-term Exposure to Outdoor Ambient PM2.5
WHO Guideline & Interim Targets
Long-term Exposure to Outdoor Ambient PM2.5
AQG IT-3 IT-2 IT-1
100 90 80 70 60 50 40 30 20 10
80% of global population exceeds WHO guideline of μg/m3
35% of East Asia exposed to >50 μg/m3 in annual mean
Estimate health effects of PM2.5 exposure
Population [%]
PM2.5 Exposure [μg/m3]
van Donkelaar et al., EHP, 2010

12. Emerging Applications
Villeneuve et al., OEM, submitted Canadian non-smokers more likely to live in areas with higher concentrations of ambient PM2.5. Cigarette smoking will act as a negative confounder in epidemiological studies of long-term ambient air pollution and mortality outcomes in Canada Hystad et al., EHP, submitted, Satellite dataset dominant contributor to national PM2.5 model Evans et al. in prep: Estimate global mortality from PM2.5 Brauer et al. in prep; Estimate global burden of disease attributable to air pollution; uses satellite estimates and global model (TM5) Burnett et al., in prep; appears that satellite estimates better than in situ at predicting mortality

13. Application of Satellite-based Estimates to Moscow Smoke Event
During Fires
Before Fires
MODIS-based
In Situ
van Donkelaar et al., in prep

14. General Approach to Estimate Surface NO2 Concentration
Method: Solar backscatter
NO2 Column
Coincident ModelProfile
In Situ
GEOS-Chem l1 l2
Scattering by
Earth surface
and atmosphere
Idealized
NO2
absorption
spectrum
S → Surface Concentration
Ω → Tropospheric column l1 l2

15. Ground-Level NO2 Inferred From OMI for 2005
Spatial Correlation vs In Situ for North America = 0.78
Lamsal et al., JGR, 2008

16. Encouraging Prospects for Satellite Remote Sensing of Air Pollutants
Challenges
Remote Sensing:
Improved algorithms to increase accuracy and observe other pollutants
Modeling:
Develop representation of processes
Measurements:
More needed for evaluation
Health Applications:
Close interaction to develop appropriate applications
Acknowledgements: Health Canada NSERC NASA