OZONE AND ITS PRECURSORS OVER THE UNITED STATES

OZONE AND ITS PRECURSORS OVER THE UNITED STATES: SOURCES, OUTFLOW, TRANSPACIFIC INFLOW, AND HEMISPHERIC INFLUENCE Rynda Hudman ACCESS Friday, August 24, 2007 ACKNOWLEDGEMENTS • Daniel Jacob and the Atmospheric Chemistry Modeling Group at Harvard • The ITCT 2 k 2, PEACE A/B, and ICARTT Science Teams • AMS/NOAA Office of Global Change Graduate Fellowship • NSF Graduate Research Fellowship

Intercontinental Influence of Ozone Alt (km) (1) primary constituent of smog in surface air [NRC, 1991] (2) 3 rd most important greenhouse gas [IPCC, 2001] 10 hn O 3 Greenhouse gas 8 NO NO 2 6 Hemispheric Pollution OH 4 HO 2 VOCs Direct Intercontinental Transport (1 week) Air quality CONTINENT 1 2 OCEAN CONTINENT 2

NORTH AMERICA : at midlatitudes we are all in each others tailpipe CO column GMAO Forecast Friday, 4/20/06 Mon, 4/24/06 CO is used as a tracer of pollution OUT IN My work uses aircraft measurements interpreted with a 3 -D model of tropospheric chemistry to examine: • Background ozone • Transpacific transport • Local surface production • Convection/Lightning • Export • Transatlantic Transport

NOAA/ITCT-2 K 2 AIRCRAFT CAMPAIGN IN APRIL-MAY 2002 Monterey, CA High-ozone Asian pollution plumes observed in lower free troposphere but not at surface (Trinidad Head) May 5 plume at 6 km: High CO and PAN, no O 3 enhancement O 3 CO PAN HNO 3 May 17 subsiding plume at 2. 5 km: High CO and O 3, PAN NOx HNO 3 Hudman et al. [2004] Measurements (NOAA WP-3 D): T. Ryerson (O 3, NOx), John Holloway (CO), Frank Flocke (PAN), Andy Neuman (HNO 3)

INTERCONTINENTAL OZONE POLLUTION LAYERS ARE FREQUENTLY OBSERVED AT HIGH ALTITUDE…BUT NOT AT SURFACE CO Aircraft observations from ITCT-2 K 2 campaign out of Monterey, CA (April-May 2002); enhancements up to 40 ppbv in high-ozone layers O 3 Dilution appears to greatly dampen ozone enhancements at surface: Trinidad Head surface observations: Asian pollution enhancement in model is 6 ± 2 ppbv May 17 Hudman et al. [2004]; Goldstein et al. [2004]

ICARTT: COORDINATED ATMOSPHERIC CHEMISTRY CAMPAIGN OVER EASTERN NORTH AMERICA AND NORTH ATLANTIC IN SUMMER 2004 SCIENTIFIC OBJECTIVES • • Regional Air Quality Continental Outflow Transatlantic Pollution Aerosol Radiative Forcing

Flash counts (flashes/km 2/s) GEOS-CHEM SIMULATION Modifications from ICARTT constraints in blue (improved) NOx Lightning Emissions Lightning X 4 over U. S. & distributed to tropopause [Price and Rind, 1992] NOx emission CO emissions May-August 2004 NA Fire Inventory [Turquety et. al, 2007] EPA National Emissions Inventory 1999 v 1 (w/ modifications to VOCs) Power plant and Industry NOx 50% Anthropogenic CO 60%

GEOS-CHEM VS. ICARTT Mean comparison along the flight tracks Large UT NOx bias Ozone FT bias 5 -10 ppbv BL bias in CO and NOx Measurements (WP-3 D, DC-8): CO (J. Holloway, G. Sachse), NOx (T. Ryerson, R. Cohen, W. Brune), PAN (F. Flocke, H. Singh), HNO 3 (A. Neuman, J. Dibb), ozone (T. Ryerson, M. Avery)

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

MEAN AFTERNOON OZONE CONCENTRATIONS 0 -1. 5 KM DURING ICARTT OBSERVED Stratified local plumes, not representative SIMULATED (NEI 99) SIMULATED (NEI 99 stationary NOx source reduced by 50%) High bias in the South and Midwest improved simulated-to-observed regression slope (afternoon, overland, 0 -1. 5 km): NEI 99: 1. 05 ± 0. 10 (R 2 = 0. 30); NEI 99 Reduced NOx: (0. 95 ± 0. 07, R 2 = 0. 34). Measurements (WP-3 D, DC-8): T. Ryerson, M. Avery

OZONE REDUCTIONS RESULTING FROM DECREASE IN NOx EMISSIONS Regional differences in ozone, can be explained by Ozone Production Efficiency (OPE): OPE Midwest: 2. 5 -3. 5 Southeast: 4 -5. 5 Can we see changes in OPE due NOx emission reductions in d. O 3/d. CO in U. S. outflow? Requires good estimate of CO source…. . GRC Poster.

OZONE-CO CORRELATIONS SHOW DECADAL INCREASE Aircraft (0 -1. 5 km, 11 -5 pm LT) ALL WIND DIRECTIONS Chebogue Point WINDS FROM W-SE Overestimate of tropical background Measurements (WP-3 D, DC-8): CO (J. Holloway, G. Sachse), ozone (T. Ryerson, M. Avery). Syrface Measurments at Chebogue Point by D. Millet Obs during the early 90 s show d. O 3/d. CO ~ 0. 3 – 0. 4 [Parrish et al. , 1998; Chin 1994] Change could be due to decadal changes in emissions

UT NOx OBSERVATIONS POINT TO A LARGER THAN EXPECTED LIGHTNING NOx SOURCE Flash Comparison GEOS-Chem [Flashes km 2 s] NLDN [ppbv] Observed NOx (8 -12 km) GEOS-Chem (Lightning X 4) NO: W. Brune, NO 2: R. Cohen/T Bertram Hudman et al. [2007 a]

MIDLATITUDE LIGHTNING PRODUCES MORE NOx/FLASH [Huntrieser et al. , 2005] [Ken Pickering] Standard GEOS-Chem mean flash rate was 125 mol flash-1 (Improved X 4 500 mol flash-1)

OZONE COMPARISON INTEX-NA SOUTHEAST U. S. Increase in lightning yield X 4 to 500 mol/flash has ~10 ppbv effect on ozone NO 2 O 3 2004 was not an anomalous lightning year Observed Simulated Improved Simulation …suggests great sensitivity of ozone to climate change Hudman et al. [2007 a]

SUMMERTIME NORTH AMERICAN OZONE ENHANCEMENTS ICARTT DC-8 ~ Equal contributions for lightning and anthropogenic emissions in free troposphere and to NH burden NA Enhancement to Hemispheric Ozone North NOx Ozone Hemispheric American Emission Production ozone Source (Tg N) Efficiency enhancement (Tg, %) Lightning 0. 28 32. 5 Biomass burning 0. 32 17. 5 Fossil fuel 0. 72 15 10. 9 (6. 1 %) All 1. 32 19 25. 6 (14. 3 %) Biomass Lightning Anthropogenic Simulated Observed All 9. 1 (5. 1%) 5. 6 (3. 1%) Hudman et al. [2007 b]

BIOGENIC VS. ANTHROPOGENIC SOURCES OF CO OVER THE UNITED STATES Aircraft (0 -1. 5 km) Both aircraft and surface data suggest NEI 99 CO emissions are 2. 5 times too high OBSERVED SIMULATED (NEI 99) (anthro CO reduced by 60%) J. Holloway, Measurments: G. Sachse, GRC Poster Measurments: A. Goldstein J. Holloway, G. Sachse