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

21st Annual International Society of Exposure Science Conference

24 October 2011

Large Regions Have Insufficient Measurements for Air Large Regions Have Insufficient Measurements for Air Pollution Exposure AssessmentPollution Exposure Assessment

Locations of Publicly-Available Long-Term PM2.5 Monitoring Sites (2001-2006)

Monitor locations can be driven by compliance objectives

~1 site / 10,000 km2 in continental US & southern Canada

Aerosol Remote Sensing: Analogy with Visibility Aerosol Remote Sensing: Analogy with Visibility Effects of Aerosol LoadingEffects of Aerosol Loading

PM2.5 = 7.6 ug m-3

Pollution haze over East Coast

Waterton Lakes/Glacier National Park

PM2.5 = 22 ug m-3

Combined AOD from MODIS and MISRCombined AOD from MODIS and MISRRejected Retrievals for Land Types with Monthly Error vs AERONET >0.1 or 20%Rejected Retrievals for Land Types with Monthly Error vs AERONET >0.1 or 20%

MODISr = 0.39

(vs. in-situ PM2.5)

MISRr = 0.39

(vs. in-situ PM2.5)

CombinedMODIS/MISR

r = 0.61 (vs. in-situ PM2.5)

0.3

0.25

0.2

0.15

0.1

0.05

0

AO

D [u

nitle

ss]

van Donkelaar et al., EHP, 2010

Calculate Coincident PMCalculate Coincident PM2.52.5/AOD with Chemical /AOD with Chemical

Transport Model (GEOS-Chem)Transport Model (GEOS-Chem)

Aaron van Donkelaar

Significant Agreement with Coincident In situ MeasurementsSignificant Agreement with Coincident In situ Measurements

SatelliteDerived

In-situ

Sat

ellit

e-D

eriv

ed

[μg/

m3]

In-situ PM2.5 [μg/m3]

Ann

ual M

ean

PM

2.5 [

μg/

m3]

(200

1-20

06)

r

MODIS τ 0.39

MISR τ 0.39

Combined τ 0.61

Combined PM2.5 0.77

van Donkelaar et al., EHP, 2010

Evaluation with measurements outside Canada/US

Global Climatology (2001-2006) of PMGlobal Climatology (2001-2006) of PM2.52.5

Better than in situ vs model (GEOS-Chem): r=0.52-0.62, slope = 0.63 – 0.71

Number sites Correlation Slope Offset (ug/m3)

Including Europe 244 0.83 0.86 1.15

Excluding Europe 84 0.83 0.91 -2.5

van Donkelaar et al., EHP, 2010

Error in Satellite-Derived PMError in Satellite-Derived PM2.52.5 has Three Primary Sources has Three Primary Sources

Satellite• Error limited to 0.1 + 20% by

AERONET filter

• Implication for satellite PM2.5

determined by η

Satellite-derived PM2.5 = 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

2.5PM

AOD Model

τa(z)/τa(z=0)

Alti

tud

e [k

m]

Evaluate GEOS-Chem Evaluate GEOS-Chem Vertical Profile with Vertical Profile with

CALIPSO ObservationsCALIPSO Observations

• Coincidently sample model and CALIPSO extinction profiles

– Jun-Dec 2006

• Compare % within boundary layer

Model (GC)CALIPSO (CAL)

Optical depth above altitude zTotal column optical depth

Error EstimateError Estimate• Estimate error from bias in profile and

AOD ±(1 μg/m3 + 15%) • Contains 68% (1 SD) of North

American data

• Total uncertainty 25% (with sampling)• Global population-weighted mean

uncertainty 7 μg/m3

van Donkelaar et al., EHP, 2010

Sat

ellit

e-D

eriv

ed

[μg/

m3]

In-situ PM2.5 [μg/m3]

van Donkelaar et al., EHP, 2010

van Donkelaar et al., EHP, 2010

Emerging ApplicationsEmerging Applications

• Estimate global outdoor air pollution exposure for global burden of disease (WHO) (Brauer et al., ES&T, submitted)

• Significant association of long-term PM2.5 exposure and cardiovascular mortality at low PM2.5 levels (Crouse et al., EHP, submitted)

• Satellite dataset dominant contributor to Canada-wide PM2.5 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)

Wildfires near Moscow in Summer 2010Wildfires near Moscow in Summer 2010

MODIS/Aqua: 7 Aug 2010

Relaxed Cloud Screening Needed for this Extreme EventRelaxed Cloud Screening Needed for this Extreme Event

van Donkelaar et al., AE, 2011

Spatial and Temporal Variation in Satellite-Based PMSpatial and Temporal Variation in Satellite-Based PM2.52.5

during Moscow 2010 Firesduring Moscow 2010 Fires

van Donkelaar et al., AE, 2011

Satellite-based Estimates of PMSatellite-based Estimates of PM2.52.5 in Moscow in Moscow

Before Fires During Fires

van Donkelaar et al., 2011

MODIS-based

In Situ PM2.5

In Situ from PM10

r2 =0.85, slope=1.06

ChallengesChallengesRemote 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 Encouraging Prospects for Satellite Remote Sensing of Air PollutantsSensing of Air Pollutants

Acknowledgements:Acknowledgements: Health Canada Health Canada NSERC NSERC NASA NASA

Health Applications:Close interaction to develop appropriate applications