1. AQUA
AURA
The Berkeley High Spatial Resolution(BEHR) OMI NO2 Retrieval: 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. L Valin et al., Atmos. Chem. Phys. 2011
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 1: DOAS fit to determine slant column
Step 2: Subtract the Stratospheric contribution
Step 3: Convert the tropospheric slant column into a vertical column
Total Slant Column Density
Stratospheric Vertical Column Density
Tropospheric Vertical 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)
NASA standard
BEHR
Terrain pressure
High-res terrain database, center of OMI footprint
High-res terrain database, average over OMI footprint
Terrain reflectivity
Monthly 1° × 1°
MODIS, 8 day 0.05° × 0.05°
NO2 profile shape
Annually 2° × 2.5°
WRF-Chem, Monthly 4 × 4 km2 (CA&NV)
12 x 12 km2 U.S.
Clouds
OMI cloud product
MODIS cloud product
Russell et al., Atmos Chem & Phys 11, , 2011

10. NASA Standard Product June 2008
Terrain Reflectivity (Albedo)
MODIS True Color
OMI Monthly Albedo
MODIS 8 day Albedo
SP NO 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. NO2 profile 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
Standard Product
BEHR
% Difference
Russell et al., Atmos Chem & Phys, 2011

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

16. molecules cm-2
Summer 2011
Russell et 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%).
Russell et al., in press

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

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

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

23. Reductions on weekdays are larger than those on weekends due to reductions in diesel traffic
2005 – – – 2011
Weekday – 6 ± 4% – 9 ± 4% – 4 ± 4%
Weekend – 7 ± 5% – 6 ± 7% – 1 ± 7%
Russell et 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,
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, , 2011
A.R. Russell, et al., A high spatial resolution retrieval of NO2 column densities from OMI: Method and Evaluation, ACP, 11, , 2011.
L.C. Valin, et al., Observation of slant column NO2 using the super-zoom mode of AURA OMI, AMT, 4, , 2011.
A.K. Mebust,, Characterization of wildfire NOx emissions using MODIS fire radiative power and OMI tropospheric NO2 columns , ACP. 11, , 2011.
R.C. Hudman, et al., Interannual variation in soil NOx emissions observed from Space, ACP. 10, , 2010.
Thank you!

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

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

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

30. Large Area+Urban Sources in WRF-Chem

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