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MODELING TRANSPORT OF OZONE AND FINE PARTICLES TO AND FROM NORTH AMERICA

MODELING TRANSPORT OF OZONE AND FINE PARTICLES TO AND FROM NORTH AMERICA. Daniel J. Jacob Harvard University. with Arlene M. Fiore, Rokjin Park, Colette L. Heald and support from EPA (ICAP), EPRI, NOAA. TWO MODES OF INTERCONTINENTAL INFLUENCE.

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MODELING TRANSPORT OF OZONE AND FINE PARTICLES TO AND FROM NORTH AMERICA

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  1. MODELING TRANSPORT OF OZONE AND FINE PARTICLES TO AND FROM NORTH AMERICA Daniel J. Jacob Harvard University with Arlene M. Fiore, Rokjin Park, Colette L. Heald and support from EPA (ICAP), EPRI, NOAA

  2. TWO MODES OF INTERCONTINENTAL INFLUENCE • Direct intercontinental transport: fast (~1 week) transport from source to receptor continent; either by boundary layer advection or by lifting to lower free • troposphere followed by subsidence • Hemispheric pollution: pollution mixes in free troposphere, affecting free tropospheric background, in turn affecting surface concentrations by subsidence Tropopause HEMISPHERIC POLLUTION BACKGROUND Mixing Free troposphere 2 km “Direct” intercontinental transport Boundary layer boundary layer advection lifting subsidence Asia N. America Europe

  3. MECHANISM FOR TRANSPACIFIC TRANSPORTOF ANTHROPOGENIC OZONE AND FINE PARTICLES HEMISPHERIC POLLUTION PAN (~10%) VOCs (long-lived) warm conveyor belts, convection subsidence O3 OC aerosol PAN Free troposphere SOx (~10%) sulfate O3 NOx 2 km Boundary layer entrainment, dilution NOx, SO2, VOC aerosols, HNO3 ozone, sulfate, OC ASIA PACIFIC NORTH AMERICA

  4. USING GLOBAL CHEMICAL TRANSPORT MODELS TO QUANTIFY INTERCONTINENTAL INFLUENCE • Standard simulation; compare w/ observations • (2) Set N. American anthropogenic emissions to zero a estimate background • (3) Set global anthropogenic emissions to zero a estimate natural background • Difference between (1) and (2) a regional pollution • Difference between (2) and (3) a intercontinental pollution • GEOS-Chem model : • driven by NASA/GEOS assimilated meteorological data • horizontal resolution 2ox2.5o, 48 vertical levels • coupled ozone-PM simulation • used by 20 research groups in Europe and N. America (~100 publications) • extensive evaluation with U.S. observations for ozone [Fiore et al., 2002, 2003ab] and PM [Park et al., 2003, 2004]

  5. * CASTNet observations Model Background Natural Stratospheric } Regional pollution D = Surface ozone at Voyageurs National Park, Minnesota (May-June 2001) } D = Intercontinental pollution + X Background: 15-36 ppbv Natural : 9-23 ppbv Stratosphere: < 7 ppbv Fiore et al. [2003]

  6. * CASTNet observations Model Background Natural O3 level Stratospheric } Regional pollution D = Surface ozone at Yellowstone National Park, Wyoming, 2.5 km altitude (March-May 2001) } D = Intercontinental pollution + X Background: 30-50 ppbv Natural : 15-30 ppbv Fiore et al. [2003]

  7. Probability distribution of afternoon (1-5 p.m. mean) surface ozone at U.S. CASTNet sites in March-October 2001 Natural 18±5 ppbv GEOS-Chem background 26±7 ppbv GEOS-Chem background 29±9 ppbv MOZART-2 Probability. ppbv-1 CASTNet observations GEOS-Chem at CASTNet Ozone, ppbv Intercontinental pollution enhances background by 8 ± 4 ppbv relative to natural Fiore et al. [2003]

  8. * CASTNet observations GEOS-Chem model Model background DEPLETION OF OZONE BACKGROUND DURING REGIONAL POLLUTION EPISODES Low-elevation CASTNet sites, Jun-Aug Regional Pollution Ozone (ppbv) Cumulative Probability Background (and intercontinental pollution influence) are highest when ozone concentrations are in mid-range (40-70 ppbv), reflecting subsidence conditions Fiore et al. [2003]

  9. GLOBAL OZONE BACKGROUND:METHANE AND NOx ARE THE LIMITING PRECURSORS Sensitivity of global tropospheric ozone inventory (Tg) to 50% global reductions In anthropogenic precursor emissions GEOS-Chem [Fiore et al., 2002a] Anthropogenic methane enhances surface ozone by 4-6 ppbv worldwide

  10. INCREASE IN FREE TROPOSPHERIC BACKGROUND OZONE OVER EUROPE IN THE PAST CENTURY Simulated historical ozone levels are higher than observed: is this due to model overestimates in natural sources (lightning) or calibration errors? Observations at mountain sites [Marenco et al., 1994] Preindustrial model ranges

  11. OBSERVED TREND IN OZONE BACKGROUND OVER CALIFORNIA IN SPRING SUGGESTS 10-15 ppbv INCREASEOVER PAST 20 YEARS Trend: 0.5-0.8 ppbv yr-1 Jaffe et al. [2003] …but this is inconsistent with models; e.g., GEOS-Chem model indicates only a 2 ppbv increase over 1980-1995 (Fiore et al., 2002b)

  12. AN EXAMPLE OF TRANSPACIFIC TRANSPORT OF ASIAN AEROSOL POLLUTION AS SEEN BY MODIS X1018 [molecules cm-2] Detectable sulfate pollution signal correlated with MOPITT CO

  13. WET SCAVENGING OF ASIAN AEROSOLS DURING LIFTING TO THE FREE TROPOSPHERE P3B DATA over NW Pacific (30 – 45oN, 120 – 140oE) TRACE-P observations over NW Pacific (Feb-Mar 2001) and GEOS-Chem simulations Sulfate is most important exported anthropogenic aerosol in model Park et al. [2005]

  14. Observed (Huebert) GEOS-Chem …BUT ELEVATED OC AEROSOL IS OBSERVED IN FREE TROPOSPHERIC ASIAN OUTFLOW – CONTRIBUTION TO INTERCONTINENTAL POLLUTION? ACE-Asia aircraft observations over Japan (spring 2001) Observed (Russell) • correlated with CO – but also a 1-3 mg sm-3 background; • implies large secondary production of OC in free troposphere missing from present models; • OC dominates aerosol loading in free troposphere OC/sulfate ratio Colette .L. Heald, Harvard

  15. INTERCONTINENTAL TRANSPORT OF ASIAN AND NORTH AMERICAN ANTHROPOGENIC SULFATE Annual mean values as determined from GEOS-Chem 2001 sensitivity simulations with these sources shut off Intercontinental enhancements of anthropogenic sulfate over U.S. are of same order as interstate enhancement threshold used for regulation (0.2 mg m-3) and EPA estimates of natural values (0.1-0.2 mg m-3) for Regional Haze Rule Park et al. [2004]

  16. VERTICAL STRUCTURE OF TRANSPACIFIC TRANSPORT GEOS-Chem model results for spring 2001 (15-45oN) Asian CO Asian sulfate N. America N. America Asia Asia Asian aerosols are transported in lower free troposphere and subside over the NE Pacific; topography in western U.S. promotes contact with surface C.L. Heald, Harvard

  17. IMPROVE GEOS-CHEM Asian anthr (GEOS-Chem) EVIDENCE OF ASIAN SULFATE IN IMPROVE NETWORKOF AEROSOL MEASUREMENTS AT U.S. SITES GEOS-Chem Asian influence spring 2001 mean 24-h seasonal max NW US: 0.60 μgm-3 NW US: 0.18 μgm-3 1.4 mg m-3 Time series over NW U.S. (spring 01) March 1 April 1 May 1 June 1 spring 2001 mean days of GEOS-Chem 24-h seasonal max IMPROVE data: NW US: 1.04 μgm-3 NW US: 0.72 μgm-3 C.L. Heald, Harvard

  18. PROBING TRANSPACIFIC POLLUTION TRANSPORT NOAA/ITCT-2K2 aircraft campaign, April-May 2002 High-ozone Asian pollution plumes observed in lower free troposphere but not at surface (Trinidad Head); strong stratospheric influence (Trinidad Head sondes) Observations by D. Parrish, J. Roberts, T. Ryesrson (NOAA/AL) May 5 plume at 6 km: High CO and PAN, no O3 enhancement CO O3 PAN May 17 subsiding plume at 2.5 km: High CO and O3, PAN gNOxgHNO3 HNO3 Hudman et al. [2004]

  19. EFFECT OF NORTH AMERICAN SOURCESON EXCEEDANCES OF EU STANDARD (55 ppbv, 8-h av.) GEOS-CHEM model results, summer 1997 Number of exceedance days (out of 92) # of exceedance days that would not have been in absence of N.American anthropogenic emissions Li et al. [2002]

  20. AIRCRAFT OBSERVATIONS IN ASIAN WARM CONVEYOR BELT (WCB) OUTFLOW ILLUSTRATE SCAVENGING OF AEROSOLS DURING LIFTING TO FREE TROPOSPHERE TRACE-P campaign out of Hong Kong and Japan, spring 2001 boundary layer outflow Aerosols scavenged from WCB outflow Ozone: WCB outflow WCB outflow Longitude Data from E.V. Browell

  21. CALIFORNIA MOUNTAIN SITES ARE MOST SENSITIVE TO ASIAN OZONE POLLUTION…because there is less dilution Observed 8-h ozone at Sequoia National Park (1800 m) in May 2002 vs. corresponding simulated (GEOS-CHEM) Asian pollution ozone enhancement Asian enhancements are 6-10 ppbv during exceedances of standard; unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions! Observed ozone (ppbv) 8-h running mean Simulated Asian ozone enhancement (ppbv) 8-h running mean Hudman et al. [2004]

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