1. Global Estimates of Ambient PM2.5 Concentrations from Satellite AOD
Aaron van Donkelaar
with contributions from:
Randall Martin, Brian Boys, Crystal Weagle, and Graydon Snider
VIIRS Aerosol Science and Operational Users Workshop
November 21-22, 2013

2. PM2.5 affects human health and longevity
Life expectancy increases 7 months per 10 μg/m3 decrease in long-term exposure
PM2.5 regulation achieved largest gains of all U.S. Federal Regulation
Dominates global environmental mortality by 2030
Particulate Matter
Ground-level Ozone
Unsafe Water Supply and Sanitation
Indoor Air Pollution
Malaria
Deaths (millions of people)
OECD, 2012
2010
2030
2050

3. Locations of Publicly Accessible Long-Term PM2.5 Monitoring Sites
Vast Regions Have Insufficient Measurements for Air Pollution Exposure Assessment
Locations of Publicly Accessible Long-Term PM2.5 Monitoring Sites
Emerging Network
Monitor locations can be driven by compliance objectives
~1 site / 10,000 km2 in continental US & southern Canada

4. Previous Global Burden of Disease Report for 2000 Impaired by Insufficient Global Observations of Fine Particulate Matter (PM2.5)
Estimate air pollution in urban areas causes:
~1 million deaths (~1%)
Could not estimate effects outside of urban areas for 2000 report
Could this be improved with satellite remote sensing?
Cohen et al., 2005

5. AOD is related to PM2.5 …but how to separate surface aerosol from column concentrations?
PM2.5 / AOD ratio is a function of:
vertical structure
aerosol type/hygroscopicity
meteorology
Multiple approaches:
surface monitors calibration
empirical relations
model output
PM2.5 / AOD
[μg/m3]
GEOS-Chem v

6. Significant agreement with coincident ground measurements over NA
MODIS AOD
0.39
MISR AOD
Combined AOD
0.61
Combined PM2.5
0.77 18 16 14 12 10 8 6 4 2
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

7. Satellite-derived PM2.5 shows global agreement
Outside Canada/US
N = 244 (84 non-EU)
r = 0.83 (0.83)
Slope = 0.86 (0.91)
Bias = 1.15 (-2.64) μg/m3
CTM Agreement:
r = 0.63 (0.72)
slope = 0.54 (0.60)
bias = 8.89 (2.45) μg/m3
Satellite-Derived PM2.5 ( ) [μg/m3]
van Donkelaar et al., EHP, 2010

8. Global impact of global data
Global Burden of Disease 2010
488 authors from 303 institutions in 50 countries
Inclusion of rural populations
PM2.5 causal role in 3 million deaths per year
Lim et al., Lancet, 2012
Inform Epidemiological Studies:
Global childhood asthma (Anderson et al., 2012)
Lung cancer in Canada (Hystad et al., 2012)
Mortality in California (Jerrett et al., 2013)
Diabetes (Brook et al., 2013; Chen et al., 2013)
Global adverse birth outcomes (Fleisher et al., in press)
Hypertension (Chen et al., in press)
Low PM2.5 cardiovascular mortality (Crouse et al., 2012)
Crouse et al., EHP, 2012

9. Global in situ monitors are sparse ...and far from AERONET
PM2.5 estimates accuracy impacted by
AOD retrieval
Simulated aerosol vertical profile
Mass to extinction conversion
Sampling (clouds/snow)
Difficult to evaluate error sources
SPARTAN network collocates PM2.5 and AOD measurements
Satellite-derived PM2.5 evaluation, analysis,
Airphoton PM2.5 (Vanderlei Martins)
Filter PM2.5
Filter PM10
3-λ Nephelometer
AOD from CIMEL Sunphotometer (e.g. AERONET)

10. CALIOP allows vertical profile correction
GEOS-Chem
CALIOP
Altitude [km] 5 4 3 2 1
Relative Profile Ratio Relative Profile
Determine profile accuracy:
Compare with CALIOP space-borne lidar
Match optical properties
Long-term ( ) comparisons 2
1.5 1
0.5
𝑒𝑥𝑡 𝑠𝑢𝑟𝑓 𝐴𝑂𝐷 𝐺𝐶 𝑒𝑥𝑡 𝑠𝑢𝑟𝑓 𝐴𝑂𝐷 𝐶𝐴𝐿
June-August
van Donkelaar et al., JGR, 2013

11. Long-term retrievals allow trends combined MODIS, MISR and SeaWiFS-based PM2.5
PM2.5 [μg/m3]
van Donkelaar et al., in prep.

12. Global exposure and trends vary by region
+0.6
Percent of Population [%]
100 80 60 40 20
Annual Mean Exposure [μg/m3]
2012
2005
1998
Year
IT1
IT3
IT2
AQG
exposure trend [μg/m3/yr]
Europe,
Central
-0.2
Asia,
South
+1.0
Western
North America,
High Income
-0.3
East
+1.4
North Africa, Middle East
+0.4
100 80 60 40 20
Percent of Population [%]
Annual Mean Exposure [μg/m3]
van Donkelaar et al., in prep

13. Some Ongoing & Future Activities
Environmental Performance Index
Operational AIRNow Satellite Data Processor
PCW/PHEOS
Chinese PM2.5 Events
PURE Air: Prospective Urban and Rural Epidemiological Study
1 km Optimal Estimation Retrieval
Size Resolved AOD/PM2.5 Calculation
ESCAPE - European Study of Cohorts for Air Pollution Effects

14. Extras

15. Short-term agreement during extreme events – Moscow 2010
120
100 80 60 40 20
PM2.5 [μg/m3]
Before Fires
July 7- July 29, 2010
During Fires
35°E °E °E
MODIS-based
In Situ PM2.5
In Situ PM2.5 from PM10
r =0.92, slope=1.06
1000
800
600
400
200
PM2.5 [μg/m3]
Jul Jul Jul Jul Aug Aug Aug Aug-18
MODIS/Aqua
Aug 7th, 2010
Moscow
50 km
van Donkelaar et al., AE, 2011

16. Error in Smoothed & Bias-corrected (2004, 2006, 2008)
Daily Satellite-based Estimates in North America Benefit from Spatial Smoothing & Bias Correction
Bias Corrected & Smoothed, Jun 27, 2005
Error in Original (2004, 2006,2008)
Error in Smoothed & Bias-corrected (2004, 2006, 2008)
van Donkelaar et al., ES&T, 2012

17. Simulated values can constrain retrievals
Optimal estimation constrains AOD retrieval by error:
GEOS-Chem provides:
AOD/PM2.5 relationship
A priori values
observed TOA
reflectance
a priori AOD
a posteriori AOD
a priori error
observational error
Satellites provide:
High resolution (0.1° × 0.1°)
Observational constraint
Column-integrated value
Available from
OE PM2.5 [μg/m3]
In situ PM2.5 [μg/m3] 40 30 20 10 15 5
OE PM2.5 [μ g/m3]
2005
van Donkelaar et al., JGR, 2013

18. Sampling Station Designed for Nearly Autonomous Operation Filter Cartridges Replaced Every Two Months Nephelometer (1 Hz) Resolves Satellite Overpass vs 24-hr
Solar Capability
8-slot Filter Cartridge
Collect PM2.5 & PM10
Cartridge Protects Filters

19. SPARTAN Activities at Dalhousie
Analysis for Ions, Metals, Black Carbon
(Ion Chromotraphy; Inductively Coupled Plasma Mass Spectrometry; Absorption )
Pre&Post Weigh Filters

20. SPARTAN Activities Beijing, China Dhaka, Bangladesh Kanpur, India
Expansion &
Supersite Development