1. Satellite Remote Sensing of the Air Quality Health Index Randall Martin, Dalhousie and Harvard-Smithsonian Aaron van Donkelaar, Lok Lamsal, Dalhousie University Xiong Liu, NASA Goddard

2. Satellite Observations Complement Ground- Based Measurements Large Regions Have Insufficient In Situ Measurements for Air Quality Assessment ~1 site / 10,000 km 2 in continental US & southern Canada In situ NO 2 measurements contaminated with NO z

3. Major Nadir-viewing Space-based Measurements of AQHI Species SensorGOMEMISRMODISSCIA- MACHY TESOMIPARA- SOL GOME -2 IASI Platform (launch)ERS-2 (1995) Terra Aqua (1999) (2002) Envisat (2002) Aura (2004) PARA- SOL (2004) MetOp (2006) Equator Crossing10:30 10:30 1:3010:001:451:309:30 Typical Res (km)320x4018x1810x1060x308x5>24x1318x1680x4012x12 Global Obs (w/o clouds) 3726n/a1110.5 AerosolXXXXXXX NO 2 XXXX OzoneXXXXXX Solar Backscatter & Thermal Infrared

4. Retrievals of Aerosol and NO 2 Most Sensitive to Boundary Layer 0.300.360.43 0.52 0.62 2.2 4.7 O 3 Aerosol O 3 NO 2 0.75 9.6 Wavelength (μm) Strong Rayleigh Scattering Weak Thermal Contrast with Surface

5. Relative Vertical Profile Affects Boundary-Layer Information in Satellite Observations Normalized Simulated (GEOS-Chem) Summer Mean Profiles over North America S(z) = shape factor C(z) = concentration Ω = column NO 2 Aerosol Extinction O3O3 Martin, AE, 2008

6. OMI Tropospheric NO 2 Column Proxy for Surface Concentration NO / NO2   with altitude October 2004 – September 2007 Inclusive

7. Promising Relationship Between Modeled and In-Situ NO 2 Profiles Martin et al., JGR, 2004 Texas AQS ICARTT Martin et al., JGR, 2006 In Situ GEOS-Chem In Situ GEOS-Chem Eastern North America New England

8. General Approach to Estimate Surface Concentration Daily Observed Column S → Surface Concentration Ω → Tropospheric column In Situ GEOS-Chem Coincident GEOS-Chem Profile MODIS/MISR AOD OMI NO 2 (DOMINO) OMI O 3 (Xiong Liu)

9. Significant Spatial Correlation from NO 2 and PM 2.5 (OMI-derived NO 2, MODIS/MISR-derived PM 2.5 ) Mean over Jun – Aug 2005 Partial AQHI (NO 2 and PM 2.5 ) y=1.4x-0.57 r=0.87 In Situ Partial AQHI Satellite-derived Partial AQHI

10. Evaluation of Surface O 3 Estimate with AQ Network O 3 Mixing Ratio (ppbv) OMI-Derived Surface O 3 for North America (Jun – Aug 2005) GEOS-Chem simulates strong correlation (r=0.9) between tropospheric O 3 Column and surface O 3 concentration during summer r=0.77 y=0.89 + 20.0

11. Significant Spatial Correlation in Satellite-derived and In Situ AQHI (OMI-derived NO 2 and O 3, MODIS/MISR-derived PM 2.5 ) Mean values over June – August 2005 for North America AQHI 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 In Situ AQHI Satellite-derived AQHI r=0.85 y=1.1x+0.47

12. Temporal Variation in the AQHI In Situ Satellite

13. Significant Correlation of Satellite-derived and In Situ AQHI Jun – Aug 2005 Correlation Coefficient

14. Challenges Remote Sensing Community: Boundary-layer ozone 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. NO 2 ) Encouraging Prospects for Satellite Remote Sensing of Air Quality