1. Using Satellite Data to Infer Surface Emissions and Boundary Layer Concentrations of NO x (and SO 2 ) Randall Martin With contributions from: Xiong Liu, Chris Sioris, Kelly Chance (Harvard-Smithsonian Center for Astrophysics) Rob Pinder, Robin Dennis (EPA/NOAA)

2. Satellite Instruments With the Capability of Remote Sensing of Tropospheric NO 2 and SO 2 Columns Nadir-viewing solar backscatter instruments including visible (NO 2 ) and ultraviolet (SO 2 ) wavelengths GOME/ERS-2 1995-2002 Spatial resolution 320x40 km 2 Global coverage in 3 days SCIAMACHY/Envisat 2002-present Spatial resolution 60x30 km 2 Global coverage in 6 days OMI/Aura 2004-present Spatial resolution 24x13 km 2 Daily global coverage

3. Spectral Fit of NO 2 Scattering by Earth surface and by atmosphere Backscattered intensity I B Solar I o Distinct NO 2 Spectrum Nonlinear least-squares fitting Ozone NO 2 O 2 -O 2 Albedo A Martin et al., 2002, 2006

4. Total NO 2 Slant Columns Observed from SCIAMACHY Dominant stratospheric background (where NO 2 is produced from N 2 O oxidation) Also see tropospheric hot spots (fossil fuel and biomass burning) May-October 2004 Retrieval Uncertainty Spectral fit 5-10x10 14 molec cm -2 Stratospheric removal 2-10x10 14 molec cm -2

5. Perform an Air Mass Factor (AMF) Calculation to Account for Viewing Geometry and Scattering  RcRc RoRo I B,o I B,c PcPc RsRs GOMECAT (Kurosu) & FRESCO Clouds Fields [Koelemeijer et al., 2002] Surface Reflectivity [Koelemeijer et al., 2003] LIDORT Radiative Transfer Model [Spurr et al., 2002] GEOS-CHEM NO 2 & aerosol profiles dd IoIo Palmer et al., 2001; Martin et al., 2002, 2003 Cloud Radiance Fraction I B,c / (I B,o + I B,c ) AMF Uncertainty 40%

6. Cloud-filtered Tropospheric NO 2 Columns Retrieved from SCIAMACHY May 2004 – Apr 2005 Martin et al., 2006 Mean Uncertainty ±(5x10 14 + 30%)

7. Tropospheric NO 2 Columns More Sensitive to Lower Tropospheric NOx NO NO 2 NOx lifetime < day Nitrogen Oxides (NO x ) Boundary Layer NO / NO2   with altitude hv NO NO 2 O 3, RO 2 hv HNO 3 NOx lifetime ~ week Ozone (O 3 ) Upper Troposphere Ozone (O 3 ) HNO 3 O 3, RO 2

8. ICARTT Campaign Over and Downwind of Eastern North America in Summer 2004 Aircraft Flight Tracks and Validation Locations Overlaid on SCIAMACHY Tropospheric NO 2 Columns NASA DC-8NOAA WP-3D Martin et al., 2006

9. Significant Agreement Between Coincident Cloud-Filtered SCIAMACHY and In-Situ Measurements r = 0.77 slope = 0.82 1:1 line Ryerson (WP-3D) Cohen (DC-8) Cloud-radiance fraction < 0.5 In-situ measurements below 1 km & above 3 km Assume constant mixing ratio below lowest measurement Add upper tropospheric profile from mean obs Horizontal bars show 17 th & 83 rd percentiles Martin et al., 2006

10. Error weighting Conduct a Chemical Inversion For NOx Emissions A posteriori emissions x Top-Down Emissions 10 15 molec N cm -2 A Priori NOx Emissions (x a ) SCIAMACHY NO 2 Columns (y) 10 11 molec N cm -2 s -1 GEOS-CHEM model F(x) min cost function SySy SaSa 1998 2004- 2005

11. Significant Agreement Between A Priori and A Posteriori Largest Discrepancy in East Asia r=0.91 Martin et al., 2006

12. A Posteriori NOx Emissions from East Asia Exceed Those from Either North America or Europe A posteriori (46 Tg N/yr) A priori (38 Tg N/yr)

13. CMAQ SCIAMACHY On-going efforts: Model Evaluation (2004) Test and Improve NOx Emission Inventories molec/cm 2 Evaluation of Modeled Spatial Distributions NO 2 Columns: Summer 2004 Rob Pinder, Robin Dennis

14. Similar discrepancies at surface Comparable spatial distributions SCIAMACHY higher in rural areas  higher regional background  missing source (lightning) or  NOx  NOy too rapid CMAQ higher downwind of urban areas (e.g., Atlanta, St. Louis), Point sources  air mass factor from GEOS-CHEM  NOx lifetime difference due to resolution Evaluation of NO 2 Spatial Distributions (contd.) Rob Pinder, Robin Dennis CMAQ Evaluation CMAQ -SCIAMACHY

15. Can Satellite Measurements of Tropospheric NO 2 Columns Provide a Proxy for Surface NO 2 In Regions Without In Situ Measurements? Highest NO 2 maximum quarterly mean by county, 2001

16. Relationship Between Surface NO 2 and GOME NO 2 Columns Northern Italy Ordonez et al., JGR, 2006 Fall/Winter Spring/Summer In Situ Measurements Corrected for NOy Contamination

17. Relationship Between Simulated (GEOS-Chem) and Measured NO 2 Profiles over Land Martin et al., 2004 Texas AQS ICARTT Martin et al., 2006 In Situ GEOS-Chem (standard) (lightning x 4) In Situ GEOS-Chem

18. CMAQ SCIAMACHY molec/cm 2 Infer Surface NO 2 from Tropospheric NO 2 Column Using Model Vertical Profile ( Courtesy: R. Martin ) Rob Pinder, Robin Dennis ppm

19. Satellite Retrieval of SO 2 Challenging! (Ozone Interference, Rayleigh Scattering <330 nm) TOMS: detect volcanic eruptions (detection limit: 4-6 DU) [Krueger, 1983; Krueger et al., 1995] GOME: detect both volcanic & anthropogenic SO 2 [Eisinger & Burrows, 1998; Khokhar et al., 2005] using the DOAS technique (detection limit: 0.5-1 DU)

20. Global Distribution of SO 2 Columns Retrieved from GOME Missing Source from Nyamuragira Volcano in October 1998 Retrieval Issues in July? GOME GEOS-Chem Xiong Liu Dobson Units Oct98 Jul97

21. Conclusions Top-down information from satellites can be applied to improve NOx emission inventories OMI will provide this capability at higher resolution Additional model development necessary for application at local scale Encouraging prospect of inferring surface NO 2 from satellite/model