The Be rkeley H igh Spatial R esolution(BEHR) OMI NO 2 Retrieval: Recent Trends in NO 2

1. AQUA AURA The Berkeley High Spatial Resolution(BEHR) OMI NO2Retrieval: Recent Trends in NO2 Ronald C. Cohen University of California, Berkeley $$ NASA

2. Air Quality Applications Of OMI NO2 • Key elements: • total columns • trends over time • differences and ratios in space • the noontime chemical lifetime of NO2 of ~1-4hrs implies an e-folding distance of order 25km • OH changes will be approximately equal to NO2 changes—a significant effect on lifetimes

3. Four Corners Power Plants: WRF-Chem L Valin et al., Atmos. Chem. Phys. 2011

4. Los Angeles: WRF-Chem

5. OMI NO2 Riyadh 8 hours 6 hours

6. Deriving NO2 column densities from space-based reflectance measurements

7. Summary of the NO2 retrieval process Step 3: Convert the tropospheric slant column into a vertical column Step 2: Subtract the Stratospheric contribution Step 1: DOAS fit to determine slant column Stratospheric Vertical Column Density Tropospheric Vertical Column Density Total Slant Column Density

8. Step 3: Convert the tropospheric slant column into a vertical column Atmosphere Absorption and Scattering by aerosols and molecules Absorption, Scattering, and Transmission through a cloud Absorption and Scattering by the surface Modified image from Richter, U Bremen Surface • AMFs are sensitive to • Viewing geometry • Terrain pressure and reflectivity • Shape (not magnitude) of the NO2 vertical profile • Clouds AMF = Vertical Column Slant Column

9. Berkeley High Resolution Retrieval (BEHR) Russell et al., Atmos Chem & Phys11, 8543-8554, 2011

10. Terrain Reflectivity (Albedo) MODIS 8 day Albedo MODIS True Color OMI Monthly Albedo SP NO2 June 18, 2008 NASA Standard Product June 2008 BEHR June 2008 Russell et al., Atmos Chem & Phys, 2011

11. Terrain Reflectivity (Albedo) PDF of systematic errors Russell et al., Atmos Chem & Phys, 2011

12. Terrain Pressure PDF of systematic errors Russell et al., Atmos Chem & Phys, 2011

13. NO2profile shape PDF of systematic errors Russell et al., Atmos Chem & Phys, 2011

14. The BEHR product is generally higher in urban regions and lower in rural regions than the operational products % Difference Standard Product BEHR Russell et al., Atmos Chem & Phys, 2011

15. molecules cm-2 Summer 2005 Russellet al., ACPD in press

16. molecules cm-2 Summer 2011 Russellet al., in press

17. Trends for select cities and power plants –– Weekdays - - Weekends –– All days Russell et al., in press

18. Trends in cities are similar while trends at power plants are more variable 47 cities, 23 power plants! Russell et al., in press

19. 2005 – 2011 reductions in urban regions of the US are similar (–32 ± 7%). Russellet al., in press

20. The impact of the economic recession on emissions is observed by OMI 2005 – 2007 Russellet al., in press

21. The impact of the economic recession on emissions is observed by OMI 2005 – 2007 2007 – 2009 Russellet al., in preparation

22. The impact of the economic recession on emissions is observed by OMI 2005 – 2007 2007 – 2009 2009 – 2011 2005 – 2007 Russellet al., in press

23. Reductions on weekdays are larger than those on weekends due to reductions in diesel traffic Weekdays: –34 ± 8% Weekends: –27 ± 10% 2005 – 2007 2007 – 2009 2009 – 2011 Weekday – 6 ± 4% – 9 ± 4% – 4 ± 4% Weekend– 7 ± 5% – 6 ± 7% – 1 ± 7% Russellet al., in press

24. Conclusions • The BEHR product reduces biases in the NO2 column due to coarse resolution terrain and profile parameters. We can make it available upon request, rccohen@berkeley.edu. • Analysis of 2005–2011 trends for cities and power plants in the US show how improved vehicle technology and the economic downturn have influenced emissions.

25. Ashley Russell Luke Valin(PhD May 2012) (PhD soon)

26. A.R. Russell, et al, Trends in OMI NO2 observations over the United States: Effects of emission control technology and the economic recession, ACPD. in press June 2012. L.C. Valin, et al, Effects of model resolution on the interpretation of satellite NO2 observations, ACP. 11, 11647-11655, 2011 A.R. Russell, et al., A high spatial resolution retrieval of NO2 column densities from OMI: Method and Evaluation, ACP, 11, 8543-8554, 2011. L.C. Valin, et al., Observation of slant column NO2 using the super-zoom mode of AURA OMI,AMT, 4, 1929-1935, 2011. A.K. Mebust,, Characterization of wildfire NOx emissions using MODIS fire radiative power and OMI tropospheric NO2 columns, ACP. 11, 5839-5851, 2011. R.C. Hudman, et al., Interannual variation in soil NOx emissions observed from Space, ACP. 10, 9943-9952, 2010. Thank you!

27. Update: Trends in urban regions of CA, 2005-2011 - 36% - 30% - 44% - 30% Russell et al., 2010 (updated)

28. CLOUDS SAMPLE (N) POLISHED MIRROR LIGHT SOURCE (Io) MOLECULES ℓ PARTICLES Beer-Lambert Law: I = Io e - σℓ N DETECTOR (I) Entangled

29. WRF-CHEM 1km – 4-Corners Plume NO2 column OH Column

30. Large Area+Urban Sources in WRF-Chem

31. NOx Lifetime By Mass τ=Mobs / Erate Integrated Observation By Decay Gradient e-kx; x = ut; τ=k-1 Resolved Observation