Dale Allen (University of Maryland; AOSC) Lisa Silverman (UMD; Civil & Environmental Eng)

1. Evaluation of CMAQ soil-NO emissions via comparison of CMAQ output and satellite-retrieved NO2 columns Dale Allen (University of Maryland; AOSC) Lisa Silverman (UMD; Civil & Environmental Eng) Sheryl Ehrman (UMD ; Chemical & Biomolecular Eng) Ken Pickering (NASA-GSFC) Heidi Plata (UMD; Chemical & Biomolecular Eng)

2. Objectives • Develop a better understanding of soil based sources of nitrogen oxides • Evaluate whether satellite observations of NO2 can be used to improve emissions estimates for soil derived NOx over the United States • Use this understanding and satellite observations to improve model estimates of NOx emissions in BEIS3, which is the biogenic emissions module used in CMAQ

3. NOx Emissions Sources over the U.S. (approximate values)

4. BEIS-3 Biogenic NO emissions (YL method) • E = R2.5 x Tadj x Padj x Fadj x Cadj • E = Time varying NO emission flux • R2.5 = Baseline NO emission flux (assumes 2.5% of fertilizer N is emitted as NO during growing season) • Tadj = temperature adjustment factor • Padj = precipitation adjustment factor (1-15). Heavy rain activates nitrifying bacteria • Fadj = fertilizer adjustment factor (1 during April and then decreases over growing season) • Cadj = canopy adjustment factor (1 during April and then decreases linearly to 0.5) Yienger & Levy (1995)

5. Magnitude and duration of YL precipitation pulse is function of rainfall amount For showers & heavy rain, substantial enhancement even 4 days after event >1.5 cm day-1 0.5<P<1.5 0.1<P<0.5 Yienger and Levy(1995)

6. Evaluation of soil NO source • Comparisons of models and satellite observations reveal a factor of 2-4 underestimate of soil-NO emissions wrt to the YL a priori estimate (Martin et al., 2003; Jaegle et al., 2005; Wang et al., 2007; Boersma et al., 2008) • YL scheme overestimates pulse duration and underestimates role of soil moisture (Hudman et al., 2010;Yan et al., 2005) • Mean 8-hr O3 enhancement of 3-5 ppbv over agricultural Great Plains during June; Hudman et al., 2010 • CMAQ simulations were performed for March – May 2006 • nosoilNO emissions • YL (standard) soilNO emissions • Doubled YL soilNO emissions Resulting tropospheric NO2 columns are compared to columns from the OMI instrument aboard the Aura satellite

7. OMI tropospheric NO2 products 1. v1.0 OMI standard product [Bucsela et al., 2008; Celarier et al., 2008] 2. v2.0 DOMINO product [Boersma et al., 2007; Boersma et al., 2011] Each algorithm begins with same slant columns (red lines) Different methods used to remove stratospheric columns Different methods used to convert tropospheric slant cols to overhead cols  Yield different tropospheric vertical column amounts tropopause

8. CMAQ nosoilNO OMI NASA Std product CMAQ YL soilNO CMAQ Dbl YL soilNO LNOx contribution est using output from GMI model (Allen et al., 2010)

9. OMI DOMINO CMAQ nosoilNO CMAQ Dbl-YL Soil-NO CMAQ YL Soil-no LNOx contribution est using output from GMI model (Allen et al., 2010)

10. Percent of tropospheric NO2 column with a soil-NO source (April-May 2006 mean) Standard YL Source (peak Contribution ~35%) Lightning-NO contribution to column from GMI model (Allen et al., 2010) Doubled YL Source (peak Contribution ~60%)

11. Model columns and 30% threshold calculated w/o LNOx

12. LNOx contribution estimated using NASA’s GMI model (Allen et al., 2010)

13. Soil-NO emissions were examined following precipitation events in the Great Plains and Midwest Screen out events if: Lightning influenced (HYSPLIT & NLDN) Biomass burning (OMI AI > 1) soilNO/totalNO emissions < 0.5

14. 16 Cases and Their Locations

15. Locations of Cases

16. Soil Moisture Precip CMAQ Column soilNO YL soil emissions CMAQ Column OMI NASA CMAQ Column Not surprisingly, cloud cover often hinders analysis

17. Soil moisture PRECIP CMAQ Column soilNO YL soil emissions OMI Column NASA product CMAQ column

18. Impact of precipitation pulsing on tropospheric NO2 columns was examined using mean time series from the 16 case studies Time series examined: Precipitation soil-NO emissions Tropospheric NO2 column (NASA standard and DOMINO) Tropospheric NO2 column (YL and doubled YL emissions) Time period examined: Day preceding precipitation event (day-1), day precipitation began (day0) to 4-days after event (day4)

21. OMI NASA cols days3-4 exceed NASA cols days0-2 by ~0.7 pmol cm-2 Considerable noise as cloud cover reduces number of cases

22. DOMINO column days 3&4 exceed DOMINO col days 0-2 by ~0.5 pmol cm-2 Considerable noise as cloud cover reduces number of cases

23. CMAQ column with std YL emissions increases by ~0.3 pmol cm-2 between days 0-1 and 2-4 (Noisy!)

24. CMAQ column with dbl YL emissions increases by ~0.5 pmol cm-2 between days 0-1 and 2-4

25. Conclusions • Soil-NO adds 8-22% to tropospheric NO2 column over US (east of 110°W) • Doubling YL soil-NO source decreases bias between model and satellite tropospheric NO2 cols over US (e of 110°W) from ~-10% to ~-2% (Effect of smoothing by averaging kernel not considered) • Over central Plains, peak soil-NO contribution to column ranges from 35-60% • Examining 16 precipitation events over central Plains regions, precipitation-pulsing increases satellite-retrieved columns by ~0.5 to 0.7 peta molecules cm-2. CMAQ columns increase by 0.3 to 0.5 (0.5 to 0.7) peta molecules cm-2 for standard YL (doubled-YL) source. However, uncertainty bars on changes are large.

26. Acknowledgements • Thomas Pierce of EPA • George Pouliot of EPA • Ana Prados of UMBC • Funding from NASA’s DSS Applied Science Air Quality Program

28. References Eskes, Henk, et al. “A combined retrieval, modelling and assimilation approach to estimate tropospheric NO2 from OMI measurements .” KNMI, De Bilt, The Netherlands. 10-12 Sept. 2010. Troposperic NO2 Measured by Satellites. J. J. Yienger and H. Levy II. “Empirical Model of Global Oil-biogenic NOx emissions.” Journal of Physical Research. 100.D6:11,447-11,464. 1995. Plata, Heidi. “Evaluating Satellite Observations to Improve Soil NOx Emissions Estimates.” 2010. Research Report. Plata, Heidi. “Towards improved emission inventories of soil NOx via model/satellite measurement intercomparisons.” 2010. Powerpoint Presentation.

30. Percent of tropospheric NO2 column with a soil-NO source

38. V1.0 NASA Std OMI product nosoilNO YL soilNO Dbl YL soilNO Note: Low-bias at least partially due to lack of lightning-NO emissions

39. nosoilNO V2.0 DOMINO Dbl YL soilNO YL soilNO Low-bias at least partially due to lack of lightning-NO emissions (LNOx) Avg kernel not applied as model profile unrealistic due to lack of LNOx

40. Percent of CMAQ’s mean April-May 2006 tropospheric NO2 column with a soil-NO source YL source Doubled YL source Note: Addition of LNOx would reduce mean percent contribution values by ~25%

41. Soil Moisture Precip Soil-NO Emission CMAQ Col soilNO CMAQ Col (total) OMI Col (NASA)