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
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
2010
2030
2050
Unsafe Water Supply
and Sanitation
Indoor Air Pollution
Malaria
0.0
1.0
2.0
Deaths (millions of people)
3.0
4.0
OECD, 2012
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
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
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
20
80
PM2.5 / AOD
[μg/m3]
Multiple approaches:
• surface monitors calibration
• empirical relations
• model output
140
GEOS-Chem v8-01-04
Significant agreement with coincident ground
measurements over NA
r
0.39
MISR AOD
0.39
Combined AOD
0.61
Combined PM2.5
0.77
16
14
12
Satellite-Derived [μg/m3]
Satellite
Derived
10
8
6
4
2
Annual Mean PM2.5 [μg/m3] (2001-2006)
MODIS AOD
18
0
In-situ
In-situ PM2.5 [μg/m3]
van Donkelaar et al., EHP, 2010
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
0
CTM Agreement:
r = 0.63 (0.72)
slope = 0.54 (0.60)
bias = 8.89 (2.45) μg/m3
5
10
15
20
50
Satellite-Derived PM2.5 (2001-2006) [μg/m3]
80
van Donkelaar et al., EHP, 2010
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:
Crouse et al., EHP, 2012
•
•
•
•
•
•
•
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)
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
• Difficult to evaluate error sources
• SPARTAN network collocates PM2.5
and AOD measurements
– Satellite-derived PM2.5 evaluation,
analysis,
• Sampling (clouds/snow)
www.spartan-network.org
Airphoton PM2.5
(Vanderlei Martins)
Filter PM2.5
Filter PM10
3-λ Nephelometer
AOD from
CIMEL
Sunphotometer
(e.g. AERONET)
CALIOP allows vertical profile correction
Altitude [km]
5
GEOS-Chem
CALIOP
4
3
2
1
00 2 4 6 8 0 0.5 1 1.5 1.9
Relative Profile Ratio Relative Profile
Determine profile accuracy:
• Compare with CALIOP
space-borne lidar
• Match optical properties
• Long-term (2006-2011)
comparisons
2
𝑒𝑥𝑡𝑠𝑢𝑟𝑓
𝐴𝑂𝐷
𝑒𝑥𝑡𝑠𝑢𝑟𝑓
𝐴𝑂𝐷
1.5
𝐺𝐶
𝐶𝐴𝐿1
0.5
June-August
2006-2011
van Donkelaar et al., JGR, 2013
Long-term retrievals allow trends
combined MODIS, MISR and SeaWiFS-based PM2.5
PM2.5 [μg/m3]
1998-2012
van Donkelaar et al., in prep.
Global exposure and trends vary by region
1998-2012 exposure trend [μg/m3/yr]
100
AQG
IT3
2005
60
1998
IT2
IT1
20
Global:
+0.6
0
5
North America,
High Income
-0.3
Asia,
East
+1.4
Europe,
Western
-0.2
Asia,
South
+1.0
40
Percent of Population [%]
Percent of Population [%]
80
60
Year
2012
80
40
100
10 15
25 35 50
100
Annual Mean Exposure [μg/m3]
20
0
80
60
40
20
0
80
60
Europe,
Central
-0.2
North Africa,
Middle East
+0.4
40
20
0
5
10 15 253550 100 5
10 15 253550 100
Annual Mean Exposure [μg/m3]
van Donkelaar et al., in prep
Some Ongoing & Future Activities
Environmental
Performance Index
Operational AIRNow Satellite
Data Processor
Chinese PM2.5 Events
PURE Air: Prospective Urban and
Rural Epidemiological Study
1 km Optimal
Estimation Retrieval
ESCAPE - EUROPEAN STUDY OF COHORTS FOR
AIR POLLUTION EFFECTS
Size Resolved
AOD/PM2.5 Calculation
PCW/PHEOS
Extras
65°N
Before Fires
July 7- July 29, 2010
120
100
During Fires
July 7- July 29, 2010
80
60°N
60
40
55°N
50°N
20
0
35°E
45°E
PM2.5 [μg/m3]
1000
55°E
35°E
45°E
55°E
r =0.92, slope=1.06
Moscow
800
MODIS-based
600
In Situ PM2.5 from PM10
400
200
PM2.5 [μg/m3]
Short-term agreement during extreme
events – Moscow 2010
MODIS/Aqua
50 km Aug 7th, 2010
In Situ PM2.5
0
Jul-14
Jul-19
Jul-24
Jul-29
Aug-03
Aug-08
Aug-13
Aug-18
van Donkelaar et al., AE, 2011
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
Simulated values can constrain retrievals
Optimal estimation constrains AOD retrieval by error:
a priori
AOD
a posteriori
AOD
J(AOD) 
 AOD
 AOD
2
σa
a
2
observed TOA
reflectance

 dρ a
ρ  

 dAOD a


2
σε
a priori error

 AOD





2
observational
error
GEOS-Chem provides:
• AOD/PM2.5 relationship
• A priori values
Satellites provide:
• High resolution (0.1° × 0.1°)
• Observational constraint
• Column-integrated value
Available from 2004-2011
15
30
10
20
10
5
0
0
10
20
30 40
In situ PM2.5 [μg/m3]
OE PM2.5 [μ g/m3]
OE PM2.5 [μg/m3]
40
0
2005
van Donkelaar et al., JGR, 2013
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
Cartridge Protects Filters
Collect PM2.5 & PM10
SPARTAN Activities at Dalhousie
Pre&Post Weigh Filters
Analysis for Ions, Metals, Black Carbon
(Ion Chromotraphy; Inductively Coupled Plasma
Mass Spectrometry; Absorption )
SPARTAN Activities
Beijing, China
Dhaka, Bangladesh
Kanpur, India
Expansion &
Supersite Development