1. GEOS-Chem Users Meeting April 12, 2007 U.S. INFLUENCE ON TROPOSPHERIC OZONE AND THE EFFECTS OF RECENT EMISSION REDUCTIONS Modeling: Rynda Hudman*, Lee Murray, Daniel Jacob, Solene Turquety, Dylan Millet, Shiliang Wu NEI 99 Emissions: Alice Gilliland ICARTT Observations: Melody Avery, Tim Bertram, Ron Cohen, Jack Dibb, Frank Flocke, Allen Goldstein, John Holloway, Andy Neuman, Tom Ryerson, Glen Sachse, Hanwant Singh, P J Wooldridge ICARTT Flight Tracks

2. North America  Europe NO x stationary sources 50% Anthropogenic CO 60% 4 2 6 8 Alt (km) 10 O 3 (ppbv) BB NA FF Lightning NO x /flash 4X larger than previously assumed! Export well constrained  effects on O 3 & OPE Northern Hemisphere Burden ICARTT CONSTRAINTS ON SUMMERTIME EMISSIONS & HEMISPHERIC OZONE

3. May-August 2004 NA Fire Inventory [Turquety et. al, 2007] EPA National Emissions Inventory 1999 v1 (w/ modifications to VOCs) Power plant and Industry NOx 50% Anthropogenic CO 60% GEOS-CHEM SIMULATION (v7.02.04 w/ modifications below) NOx Lightning Emissions Lightning X4 over U.S. & distributed to tropopause [Price and Rind, 1992] Modifications from ICARTT constraints in blue (improved) Flash counts (flashes/km 2 /s) CO emissions NO x emission

4. GEOS-CHEM VS. ICARTT Mean comparison along the flight tracks Large UT NO x bias BL bias in CO and NO x Ozone FT bias 5-10 ppbv Measurements (WP-3D, DC-8): CO (J. Holloway, G. Sachse), NO x (T. Ryerson, R. Cohen, W. Brune), PAN (F. Flocke, H. Singh), HNO 3 (A. Neuman, J. Dibb), ozone (T. Ryerson, M. Avery)

5. Observed Simulated Improved Simulation DC-8 Midwest Median NO 2 Median Model / Observed NO x (0-2 km) [ratio] Large overestimate powerplant/industry dominated Midwest and in the South 50% reduction in power and industry source as determined by Frost et al., [2006] improves boundary layer NO 2 simulation ICARTT OBSERVATIONS CONFIRM LARGE DECREASE SINCE 1999 IN INDUSTRY/POWER SOURCE Measurements (WP-3D, DC-8): T. Ryerson (NO 2 ), Ron Cohen/Tim Bertram (NO 2 ) NO 2 (ppbv)

6. OZONE REDUCTIONS RESULTING FROM DECREASE IN NO x EMISSIONS Can we see changes in OPE due NO x emission reductions in dO 3 /dCO in U.S. outflow? Requires good estimate of CO source….. Regional differences in  ozone, can be explained by OPE: OPE Midwest: 2.5-3.5 Southeast: 4-5.5

7. BOTH AIRCRAFT AND SURFACE DATA SUGGEST NEI 99 CO EMISSIONS ARE 2.5 TIMES TOO HIGH Aircraft (0-1.5 km) Chebogue Point (surface) OBSERVED SIMULATED (NEI99 ) SIMULATED (anthro CO reduced by 60%) Measurments: J. Holloway, G. Sachse Measurments: A. Goldstein/ Dylan Millet Hudman et al. [2007b]

8. SCATTERPLOT OF SIMULATED TO OBSERVED CO Parrish [2006] finds on-road source overestimated by 50% in NEI 99 (  ~33% reduction in NEI source due to this bias) CO decrease trend 3.7% yr -1 (1987-2002), (  12% reduction in anthropogenic CO source since 1999 due to trend)  From these estimates 2004 emissions 45% lower than NEI 99 (Our estimate 60%)

9. ANTHROPOGENIC CO SOURCE IN THE UNITED STATES IN SUMMER IS NOW LOWER THAN BIOGENIC SOURCE CO ANTHROPOGENIC EMISSION (11.5, 4.6) CO SOURCE FROM ANTHROPOGENIC VOC OXIDATION (1.8, 1.8) CO SOURCE FROM ISOPRENE OXIDATION (6.7, 6.7) CO SOURCE FROM OTHER BIOGENIC OXIDATION (2.4, 2.4) NEI 99NEI 99 with 60% reduction in CO CO SOURCE FROM OTHER BIOMASS BURNING OVER CONTINENTAL U.S.(0.16, 0.16)  Note: Fires in Canada and Alaska ~19 Tg CO SOURCE TYPE (Tg CO)

10. OZONE-CO CORRELATIONS SHOW DECADAL INCREASE Obs during the early 90s show dO 3 /dCO ~ 0.3 – 0.4 [Chin et al., 1994; Parrish et al., 1998]. Change consistent with decadal changes in emissions and OPE over the Northeaster United States Overestimate of tropical background WINDS FROM W-SE ALL WIND DIRECTIONS Aircraft (0-1.5 km, 11-5pm LT) Chebogue Point

11. SUMMERTIME NORTH AMERICAN OZONE ENHANCEMENTS Biomass Lightning Anthropogenic Simulated Observed All North American Source NO x Emission (Tg N) Ozone Production Efficiency Hemispheric ozone enhancement (Tg, %) Lightning0.2832.59.1 (5.1%) Biomass burning 0.3217.5 5.6 (3.1%) Fossil fuel0.721510.9 (6.1 %) All1.32 19 25.6 (14.3 %) NA Enhancement to Hemispheric Ozone ICARTT DC-8 ~ Equal contributions for lightning and anthropogenic emissions in free troposphere and to NH burden

13. OBSERVED dO 3 /dCO INCREASE OVER THE PAST DECADE CONSISTENT WITH UNDERSTANDING OF OPE AND SOURCES dO 3 /dCO  OPE (dO 3 /dNOx) * NO x /CO source ratio (dNO x /dCO ) Consider NE U.S., July 1 – August 15, 2004 (With ICARTT Constraints) Anthro = 1.2 Tg CO, 0.10 Tg N Biogenic = 0.87 Tg CO July 1 – August 1994 4.9% anthro decrease/year in urban air [Parrish, 2006]  Total CO 26% higher 22% stationary NO x reduction [Hudman et al., 2007]  Anthro NO x 15% higher  OPE lower by ~9%  NO x /CO source ratio lower by ~19% ~28% increase in dO 3 /dCO expected 0.3-0.4 (90s)  0.4-0.5 (present) Multiply dO 3 /dCO * ECO  1.5 Gmol ozone d -1 ( Ozone flux consistent with 1990s estimates)

14. Fuel - based inventory + CO & CO/NO x ambient trends  inferred emissions [Parrish et al., 2006] EVALUATION OF EPA NEI99 ON-ROAD TRANSPORT EMISSIONS On-road emission estimates *Note: 2004 trends report is same as NEI99 On-Road transport inventories (1995) On-road CO emissions too high by 50%

15. UNITED STATES NO x REGULATIONS AIMED AT REDUCING OZONE SMOG 1998 - The EPA NO x SIP Call mandated that 22 eastern states & DC revise their SIPs to meet NO x emissions reductions by 2003 (Phase 1) and further reduction by 2007 (Phase 2). 2003 - All 22 states reduced NO x point source emissions to their Phase 1 levels. 2004 - Frost et al., [2006] determined that as a result emission rates of power plant NO x have decreased approximately 50% between 1999 and 2003. 2005 - NOx levels in the U.S. will likely continue to drop. In March 2005, the EPA issued the Clean Air Interstate Rule, which will, permanently reduce NO x emissions to 60% of 2003 levels in 25 eastern states, and the DC. 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 50% NOx PP reduction Frost et al., [2006] NOx SIP SIP Phase 1 SIP Phase 2 CAIR

16. Frost et al., [2006]

17. CO OVERESTIMATE IS NOT CAUSED BY INSUFFICIENT VENTILATION OR BIOGENIC SOURCE Boundary layer ventilation is constrained by vertical profile of short-lived VOCs Biogenic VOCs are well- constrained by successful simulation of formaldehyde Propane: E. Atlas CH 2 O: Alan Fried

18. [Provided by D. Millet] CHEBOGUE POINT CO TIMESERIES Bias still exists during outflow events 7/18/1

19. UT NO x OBSERVATIONS POINT TO A LARGER THAN EXPECTED LIGHTNING NO x SOURCE Hudman et al. [2007a] GEOS-Chem (Lightning X4)Observed NO x (8-12 km) [ppbv] DOESN’T APPEAR TO BE A NO x LIFETIME ISSUE NO: W. Brune, NO 2 : R. Cohen/T Bertram

20. Lightning parameterization (flashes/km 2 /s): Land : ~CTH 4.9, Ocean: ~CTH 1.73 CTH= Cloud Top Height Price and Rind [1992] GEOS-Chem Vertical Distribution GEOS-Chem NLDN [ Flashes km 2 s] FLASH RATES WELL SIMULATED POINTING TO A LARGER YIELD/FLASH AT NORTHERN MIDLATITUDES Flash Comparison Pickering et al., [1998]

21. [Huntrieser et al., 2005] PEAK CURRENT AS A FUNCTION OF LATITUDE

22. [Ken Pickering] NO PRODUCTION RATE CALCULATED FROMR RECENT CAMPAIGNS Standard GEOS-Chem mean flash rate was 125 mol flash -1 (Improved  X4  500 mol flash -1 )

23. OZONE COMPARISON INTEX-NA SOUTHEAST U.S. Increase in lightning yield X4 to 500 mol/flash has ~10 ppbv effect on ozone NO 2 O3O3 Hudman et al. [2007a] …suggests great sensitivity of ozone to climate change Observed Simulated Improved Simulation 2004 was not an anomalous lightning year

24. Hudman et al. [2007b] NORTH AMERICAN ENHANCEMENT TO HEMISPHERIC OZONE