1. Applications of Satellite Remote Sensing to Estimate Global Ambient Fine Particulate Matter Concentrations Randall Martin, Dalhousie and Harvard-Smithsonian with contributions from Aaron van Donkelaar, Dalhousie University Rob Levy, Ralph Kahn NASA Michael Brauer, UBC Michal Krzyzanowski, WHO Aaron Cohen, HEI 21 st Annual International Society of Exposure Science Conference 24 October 2011

2. Large Regions Have Insufficient Measurements for Air Pollution Exposure Assessment Locations of Publicly-Available Long-Term PM 2.5 Monitoring Sites (2001-2006) Monitor locations can be driven by compliance objectives ~1 site / 10,000 km 2 in continental US & southern Canada

3. Aerosol Remote Sensing: Analogy with Visibility Effects of Aerosol Loading PM 2.5 = 7.6 ug m -3 Pollution haze over East Coast Waterton Lakes/Glacier National Park PM 2.5 = 22 ug m -3

4. Combined AOD from MODIS and MISR Rejected Retrievals for Land Types with Monthly Error vs AERONET >0.1 or 20% MODIS r = 0.39 (vs. in-situ PM 2.5 ) MISR r = 0.39 (vs. in-situ PM 2.5 ) Combined MODIS/MISR r = 0.61 (vs. in-situ PM 2.5 ) 0.3 0.25 0.2 0.15 0.1 0.05 0 AOD [unitless] van Donkelaar et al., EHP, 2010

5. Calculate Coincident PM 2.5 /AOD with Chemical Transport Model (GEOS-Chem) Aaron van Donkelaar

6. Significant Agreement with Coincident In situ Measurements Satellite Derived In-situ Satellite-Derived [ μ g/m3] In-situ PM 2.5 [μg/m 3 ] Annual Mean PM 2.5 [ μ g/m 3 ] (2001-2006) r MODIS τ 0.39 MISR τ 0.39 Combined τ 0.61 Combined PM 2.5 0.77 van Donkelaar et al., EHP, 2010

7. Evaluation with measurements outside Canada/US Global Climatology (2001-2006) of PM 2.5 Better than in situ vs model (GEOS-Chem): r=0.52-0.62, slope = 0.63 – 0.71 Number sitesCorrelationSlopeOffset (ug/m 3 ) Including Europe2440.830.861.15 Excluding Europe840.830.91-2.5 van Donkelaar et al., EHP, 2010

8. Error in Satellite-Derived PM 2.5 has Three Primary Sources Satellite Error limited to 0.1 + 20% by AERONET filter Implication for satellite PM 2.5 determined by η Satellite-derived PM 2.5 = AOD Model Affected by aerosol optical properties, concentrations, vertical profile, relative humidity Most sensitive to vertical profile [van Donkelaar et al., 2006] Sampling Biases Satellite retrievals are at specific time of day for cloud-free conditions

9. τ a (z)/τ a (z=0) Altitude [km] Evaluate GEOS-Chem Vertical Profile with CALIPSO Observations Coincidently sample model and CALIPSO extinction profiles –Jun-Dec 2006 Compare % within boundary layer Model (GC) CALIPSO (CAL) Optical depth above altitude z Total column optical depth

10. Error Estimate Estimate error from bias in profile and AOD ±(1 μg/m 3 + 15%) Contains 68% (1 SD) of North American data Total uncertainty 25% (with sampling) Global population-weighted mean uncertainty 7 μg/m 3 van Donkelaar et al., EHP, 2010 Satellite-Derived [ μ g/m3] In-situ PM 2.5 [μg/m 3 ]

11. van Donkelaar et al., EHP, 2010

13. Emerging Applications Estimate global outdoor air pollution exposure for global burden of disease (WHO) (Brauer et al., ES&T, submitted) Significant association of long-term PM 2.5 exposure and cardiovascular mortality at low PM 2.5 levels (Crouse et al., EHP, submitted) Satellite dataset dominant contributor to Canada-wide PM 2.5 model (Hystad et al., EHP, 2011) Cigarette smoking is a negative confounder in epidemiological studies of long-term ambient air pollution and mortality outcomes in Canada (Villeneuve et al., OEM, 2011)

14. Wildfires near Moscow in Summer 2010 MODIS/Aqua: 7 Aug 2010

15. Relaxed Cloud Screening Needed for this Extreme Event van Donkelaar et al., AE, 2011

16. Spatial and Temporal Variation in Satellite-Based PM 2.5 during Moscow 2010 Fires van Donkelaar et al., AE, 2011

17. Satellite-based Estimates of PM 2.5 in Moscow Before Fires During Fires van Donkelaar et al., 2011 MODIS-based In Situ PM 2.5 In Situ from PM 10 r 2 =0.85, slope=1.06

18. Challenges Remote Sensing: Improved algorithms to increase accuracy and resolution Modeling: Develop representation of vertical profile Measurements: More needed for evaluation throughout the world Encouraging Prospects for Satellite Remote Sensing of Air Pollutants Acknowledgements: Health Canada NSERC NASA Health Applications: Close interaction to develop appropriate applications