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

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

Aaron van Donkelaar

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

7.6 ug m-3

22 ug m-3

Pollution haze over East Coast

Waterton Lakes/Glacier National Park

Combined Aerosol Optical Depth (AOD)Combined Aerosol Optical Depth (AOD) from MODIS and from MODIS and MISR Instruments for 2001-2006MISR Instruments for 2001-2006

CombinedMODIS/MISR

r = 0.63 (vs. in-situ PM2.5)

van Donkelaar et al., EHP, 2010

Chemical Transport Model (GEOS-Chem) Chemical Transport Model (GEOS-Chem) Simulation of Aerosol Optical Depth Simulation of Aerosol Optical Depth

Aaron van Donkelaar

Ground-level “Dry” PMGround-level “Dry” PM2.52.5 = = ηη · AODAOD

η affected by vertical structure, aerosol properties, relative humidityObtain η from aerosol-oxidant model (GEOS-Chem) sampled coincidently with satellite obs

GEOS-Chem Simulation of η for 2001-2006

van Donkelaar et al., EHP, 2010

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 0.40

MISR τ 0.54

Combined τ 0.63

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 Bias (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

van Donkelaar et al., EHP, 2010

van Donkelaar et al., EHP, 2010

• 80% of global population exceeds WHO guideline of 10 μg/m3

• 35% of East Asia exposed to >50 μg/m3 in annual mean

• Estimate health effects of PM2.5 exposure

PM2.5 Exposure [μg/m3]

Long-term Exposure to Long-term Exposure to Outdoor Ambient PMOutdoor Ambient PM2.52.5

van Donkelaar et al., EHP, 2010

100

90

80

70

60

50

40

30

20

10

0

AQG IT-3 IT-2 IT-1

Pop

ulat

ion

[%]

5 10 15 25 35 50 100

WHO Guideline & Interim Targets

Emerging ApplicationsEmerging 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

Application of Satellite-based Estimates to Moscow Application of Satellite-based Estimates to Moscow Smoke EventSmoke Event

Before Fires During Fires

van Donkelaar et al., in prep

In Situ

MODIS-based

General Approach to Estimate Surface NOGeneral Approach to Estimate Surface NO22 Concentration Concentration

NO2 Column

S → Surface Concentration

Ω → Tropospheric column

In Situ

GEOS-Chem

Coincident ModelProfile

OM

MO S

S

Method: Solar backscatter

Scattering by Earth surface and atmosphere

IdealizedNO2

absorptionspectrum

Ground-Level NOGround-Level NO2 2 Inferred From OMI for 2005 Inferred From OMI for 2005

Lamsal et al., JGR, 2008

Spatial Correlation vs In Situ for North America = 0.78

ChallengesChallengesRemote Sensing: Improved algorithms to increase accuracy and observe

other pollutants

Modeling: Develop representation of processes

Measurements: More needed for evaluation

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