1

Satellite Remote Sensing of Particulate

Matter Air Quality

ARSET-AQApplied Remote SEnsing

Training

A project of NASA Applied Sciences

Pawan GuptaOriginally presented at

LADCO, March 12-15, 2012

Estimation of PM2.5 mass concentration at surface (µg m-3) while utilizing satellite derived Aerosol

Optical Depth (AOD – unitless quantity) at a visible wavelength

OBJECTIVE

Sensitive groups should avoid all physical activity outdoors; everyone else should avoid prolonged or heavy exertion

Sensitive groups should avoid prolonged or heavy exertion; everyone else should reduce prolonged or heavy exertion

Sensitive groups should reduce prolonged or heavy exertion

Unusually sensitive people should consider reducing prolonged or heavy exertion

None

Cautionary Statements

201-300

151-200

101-150

51-100

0-50

IndexValues

PM10

(ug/m3)

PM2.5

(ug/m3)

Category

355-424

255-354

155-254

55-154

0-54

150.5-250.4

65.5-150.4

40.5-65.4

15.5-40.4

0-15.4Good

Very Unhealthy

Unhealthy

Unhealthy for Sensitive Groups

Moderate

What are we looking for ?

Surface

Aerosol

Rayleigh Scattering

Water vapor + other gases (absorption)

Ozone

10km

Satellite

Sun

ColumnSatelliteMeasurement

Particle size Composition Water uptake Vertical Distribution

Satellite retrieval issues - inversion (e.g. aerosol model, background).

Seven Seven MODIS MODIS bandsbandsare are utilized to utilized to derivederiveaerosol aerosol propertiesproperties

0.470.47, , 0.55, 0.55, 0.650.65, , 0.86, 0.86, 1.24, 1.24, 1.64, 1.64, and and 2.132.13 µmµm

10X10 10X10 kmkm22 Res.Res.

dzAOT ext )(

What Do Satellites Provides?

Measurement Techniques

AOD – Column integrated value (top of the atmosphere to surface) - Optical measurement of aerosol loading – unitless. AOD is a function of shape, size, type and number concentration of aerosols

PM2.5 – Mass per unit volume of aerosol particles less than 2.5 µm in aerodynamic diameter at surface (measurement height) level

What satellites provide and how to get it?

DRAFT

May 11, 2007

May 12, 2007

May 13, 2007

May 14, 2007

May 15, 2007

May 16, 2007

MODIS-Terra True Color Images

DRAFT

May 11, 2007

May 12, 2007

May 13, 2007

May 14, 2007

May 15, 2007

May 16, 2007

MODIS-Terra Aerosol Optical Thickness

AOT to PM

Hoff and Christopher, 2009

AOD to PM2.5 - Theoretical

PM2.5 Estimation: Popular Methods

AOT

PM

2.5

Y=mX + c5D+

2D+

1

1D+

and Empirical Methods, Data Assimilation etc. are under utilized

AOT-PM

Chu et al., 2003

Wang et al., 2003

Gupta, 2008

AOT-PM2.5 Relationship

Limitation: Major Unsolved Issue

All three Statistical models (TVM, MVM, ANN) underestimate high PM2.5 loadings

Vertical Distribution

Engel-Cox et al., 2006Al-Saadi et al., 2008

Aug 17Aug 18Aug 19

Aug 20Aug 21Aug 22Aug 23

Aug 25Aug 28

5 km

(courtesy of Dave Winker, P.I. CALIPSO)

What Satellites can provide for vertical What Satellites can provide for vertical information? - CALIPSOinformation? - CALIPSO

Questions to Ask: Issues

How accurate are these estimates ?

Is the PM2.5-AOT relationship always linear?

How does uncertainty in AOT retrievals affect estimation of air quality

Does this relationship change in space and time?

Does this relationship change with change in aerosol type?

How does meteorology drive this relationship?

How does vertical distribution of aerosols in the atmosphere affect these estimates?

TVM MVM

Advantages of using reanalysis meteorology along with satellite

TVM

MVM ANN

Spatial Comparison

MODIS-Terra, July 1, 2007

Satellite-derived PM2.5 fills the gap in surface measurements

All three methods underestimate the higher PM2.5 concentrations.

Gupta et al., 2010, to be submitted

Combination of model and satellite observations

van Donkelaar et al., 2010