1. Folkert Boersma Collaborators: Daniel J. Jacob, Miri Trainic, Yinon Rudich, Ruud Dirksen, and Ronald van der A Comparison of NO 2 air pollution in Israeli cities measured from the ground and from SCIAMACHY and OMI Dutch OMI NO 2 product DOMINO (www.temis.nl)

2. Motivation Trends in emissions Can we use satellite measurements of NO 2 to obtain better estimates of NO x emissions? Monitoring of a target polluter Is tropospheric NO 2 a proxy for near-surface NO 2 ? Boersma et al., Atmos. Environ., 2008

3. Comparison of surface and satellite NO 2 Different quantities and error budgets: near-surface concentrations vs. trop. columns point measurements vs. spatial average interference from NO z vs. AMF errors BUT: Validation still sparse, especially on larger spatial and longer temporal scales Allows for validation of diurnal cycle Interference Ground-based instruments with molybdenum converter overestimate NO 2 Interference from HNO 3, PAN, alkyl nitrates Effect largest in summer (photochemistry) for regions downwind of sources Schaub et al., ACP, 2006

4. 8 urban stations in Israel 8 urban stations in Israel Half-hourly NO 2 & O 3 concentrations Half-hourly NO 2 & O 3 concentrations Molybdenum converters Molybdenum converters

5. Known issues with in situ NO2 Summarize Dunlea et al. Dunlea et al., (ACP, 2007)

6. Very little interference at 10:00 (fresh emissions, little photochemical processing yet) Interference modest at 13:30 Interference correlates with ambient O 3 concentration, but O 3 itself does not represent an interference What does this mean for urban, in situ NO 2 ? slope = 0.1 Israeli cities: no specific NO 2 measurements available, but we have in-situ observed O 3

7.  O 3 = O 3 [13:30] – O 3 [10:00] Dunlea et al.: interference = 0.1  O 3 Two limiting cases: –no correction at all –correcting NO 2 at 13:45 as follows: Interference correction based on in situ O 3 slope = 0.09slope = 0.24 slope = 0.10

8. Δlat,lon < 0.1° OMI VZA < 35° f clrad < 50%

9. No correction Δlat,lon < 0.1° OMI VZA < 35° f clrad < 50% r = 0.61 (n=396) RMA: y = -1.28 + 0.90x

10. No correction Δlat,lon < 0.1° OMI VZA < 35° f clrad < 50% r = 0.54 (n=396) RMA: y = -0.68 + 0.92x Uniform correction (-8%)

11. Assume well-mixed boundary-layer Extrapolate surface NO 2 throughout the BL depth Seasonal variation in noontime BL depths over Israel from Dayan et al. [1988, 2002] Boundary-layer columns from surface NO 2 1091 790 608 DJF MAM, SON JJA NO 2 (ppb) z (m) Summertime subtropical high is associated with subsidence of FT air, “capping” the BL.

12. Boundary-layer columns from surface NO 2 Column-column comparison No interference correction: y = -0.86 + 0.90 x Interference correction: y = -0.35 + 0.94 x Surface – OMI vs.BL column - OMI No correction

13. Seasonal variation in surface and OMI NO 2 columns

14. Weekly cycle in surface and OMI NO 2 columns Beirle et al. (ACP, 2004)

15. Diurnal cycle in NO 2 columns? NO 2 NO 2 : NO x E k NO 2 +OH+M  HNO 3 +M Boersma et al., JGR, 2008

16. Diurnal cycle in surface-based and satellite NO 2 n = 26 Δlat,lon < 0.1° f clrad < 50%

17. Diurnal cycle in surface-based and satellite NO 2

18. MAM

21. Diurnal cycle in surface-based and satellite NO 2

22. END Dutch OMI NO 2 product DOMINO (www.temis.nl)

23. NO x emission inventories in need of verification New set of emission inventories EDGAR (global) Streets et al. 2006 EMEP (Europe) Lin Zhang et al. (2008) Konovalov et al., ACPD, 2008 GOME, SCIAMACHY (1996-2005) EMEP (1996-2005)

24. Trend 1996-2006 from GOME, SCIAMACHY Figure NO x emissions show trends in the Middle East Cairo+ 1.3%/yr Tehran+ 6.1%/yr Calcutta+ 2.2%/yr Delhi+ 7.4%/yr 1996-2006

25. NO x emissions show trends in the Middle East 1996-20021996-2006 Richter et al., 2005van der A et al., 2008

26. Effect of averaging kernel a: scattering weights x TM4 : TM4 NO 2 profile b:forward model parameters MIGEOS-Chem with AK GEOS-Chem direct

27. Effect of averaging kernel N GC = ∑x GC, l GEOS-Chem with AK N GC,AK = ∑A l ·x GC, l N OMI = ∑A l ·x true, l OMI

28. Effect of averaging kernel OMI GEOS-Chem with AK GEOS-Chem direct r (gc,omi)= 0.71 r (gc_ak,omi)= 0.75 N gc = 0.87 N gc_ak = 0.93 (+7%) N omi = 1.09 GEOS-Chem direct

29. Write N GC,AK > N GC differently: Definition of tropospheric air mass factor: Substitute tropospheric air mass factor: Or ( S GC = scatt. weights · GEOS-Chem NO2 profile ): What does N GC,AK > N GC mean?

30. Mean NO 2 profiles over Middle East for 1-7 February 2006 from TM4 and GEOS-Chem

31. Correcting for background NO 2 Can we simply subtract UT NO2 at mid-latitudes? Lin Zhang et al., 2008 Rynda Hudman et al., JGR, 2007 Randall Martin, 2006

32. Checking GEOS-Chem background NO 2 with OMI

33. Qinbin paper Duncan paper

34. Comparison of ground-based to GOME NO 2 Ordonez et al. (ACP, 2006) Compares 7 years of data over Po Valley to GOME NO2 Regional comparison (~10.000 km2) Struggles with interference for ground-based stations

35. Comparison of ground-based to SCIAMACHY NO 2 Blond et al. (2006) Compares 1 year of data over northwestern Europe to SCIAMACHY NO 2 Regional comparison (1.800 km 2 ) No interference correction for ground-based stations Best agreement for rural stations All stations Rural stations Differences attributed to (lack of) spatial representativity of stations Annual mean 2003

36. Boundary-layer columns from surface NO 2 y = -0.35 + 0.70 x If Δlat,lon < 0.1° as for OMI: r = 0.65, n = 32 y = -0.47 + 0.93x Surface – SCIAMACHY vs. BL column - SCIAMACHY No correction y = -0.32 + 0.82 x n = 135 Δlat,lon < 0.25°