Aura NO2 talk

1
Satellite Remote Sensing of a Multipollutant Air
Quality Health Index
Randall Martin, Dalhousie and Harvard-Smithsonian
Lok Lamsal, Aaron van Donkelaar, Dalhousie
University Xiong Liu, NASA Goddard OMI NO2
Team SEARCH NO2 Team
2
Multipollutant Air Quality Health Index (AQHI)

• Use Canadian AQHI (Stieb et al., JAWMA, 2008)

AQHI
Excess Mortality Risk ()
Retrievals of Aerosol and NO2 Most Sensitive to
Boundary Layer
Weak Thermal Contrast with Surface
Strong Rayleigh Scattering
O3
O3
Aerosol
NO2
9.6
2.2
4.7
0.52
0.62
0.75
0.30
0.36
0.43
Wavelength (µm)
3
Relative Vertical Profile Affects Boundary-Layer
Information in Satellite ObservationsNormalized
Simulated (GEOS-Chem) Annual Mean Profiles over
North America
S(z) shape factor C(z) concentration O
column
Aerosol Extinction
SO2
NO2
O3
CO
HCHO
Martin, AE, 2008
4
General Approach to Estimate Surface Concentration
Coincident Model Profile
Daily Observed Column

• S ? Surface Concentration
• O ? Tropospheric column

5
Combine MODIS and MISR AOD by Performance vs
AERONET
MODIS
MISR
Retain Retrievals with Low Bias (lt20 or 0.1) vs
AERONET AOD for Land Type
Annual mean 2001-2006
Combined
white space lt10 obs/year
Aaron van Donkelaar
6
Evaluate Combined Surface PM2.5 Estimate with In
Situ
Annual Mean 2001-2006
r0.78, slope 0.81
n898
MODIS alone r0.66 MISR alone r0.68
Aaron van Donkelaar
7
Large Differences Between OMI NO2 Products
Direct Validation Has Not Arbitrated
Standard Product
1015 molec cm-2
Near-Real Time Product
Collection 3
Lok Lamsal
8
Multiple Indirect Validation Approaches Yield
Similar Conclusions
Corrected surface NO2 AQ Network
SEARCH True Surface NO2
Eastern NA 34 rural sites
Southeast US 3 rural sites
Eastern North American Emissions
(NEI1999 scaled to 2005)
Emissions over SEARCH Domain
Lok Lamsal
Collection 3
9
Surface O3 Estimate from OMI Tropospheric O3
Column and GEOS-Chem O3 Profile (Shape Factor)
GEOS-Chem Shape Factors
OMI Tropospheric O3 (Xiong Liu)
Tropospheric O3 Column (DU)
North America (Summer 2005)
10
Evaluation of Surface O3 Estimate with AQ Network
r0.64 w/o California
North America (Summer 2005) Change to May-Sept
11
Why is the OMI-derived Surface O3 Estimate So
Good?
Strong Relationship Between Tropospheric O3
Column and Surface O3 Concentration During Summer
North America (Summer)
12
Significant Spatial Correlation in
Satellite-derived and In Situ AQHI (OMI-derived
NO2 and O3, MODIS/MISR-derived PM2.5)
Mean values over May September 2005 for North
America
AQHI
13
Significant Correlation of Satellite-derived and
In Situ AQHI
Temporal Correlation Between In Situ and
Satellite-derived AQHI (May Sept 2005)
Correlation Coefficient
14
Challenges
Encouraging Prospects for Satellite Remote
Sensing of Air Quality
Remote Sensing Community Boundary-layer
ozone Resolve inter-retrieval differences
Higher spatial resolution obs (urban scales,
cloud-free, validation)
Modeling Community Develop representation of
vertical profile Comprehensive assimilation
capability

• Measurement Community
• Develop robust validation networks
• vertical profile
• span satellite footprint
• full year
• research quality (e.g. NO2)

15
Extra
16
Promising Relationship Between Modeled and
In-Situ NO2 Profiles
In Situ GEOS-Chem
Texas AQS
Martin et al., 2004
Eastern North America
New England
In Situ GEOS-Chem
ICARTT
Martin et al., 2006