INTERCONTINENTAL TRANSPORT OF OZONE AND AEROSOLS Daniel J. Jacob and support from NOAA, EPRI, NASA, EPA (ICAP) with T. Duncan Fairlie, Colette L. Heald, Rynda C. Hudman, Rokjin J. Park, Solene Turquety, Lyatt Jaegle (UW)

INTERCONTINENTAL TRANSPORT OF OZONE POLLUTION: SUMMARY OF PREVIOUS WORK AT HARVARD Anthropogenic NO x and NMVOC emissions outside North America enhance surface ozone over the U.S. by 2-6 ppbv on average; influence is maximum when ozone is in mid-range (40-70 ppbv) but low under stagnation conditions conducive to pollution episodes [Fiore et al., 2002a] Anthropogenic methane emissions increase surface ozone by another 4-6 ppbv through increase in the ozone background [Fiore et al., 2002b] 50% of exceedances of the (55 ppbv, 8-h avg.) air quality standard in Europe would not happen in the absence of N. American NO x and NMVOC emissions [Li et al., 2002] Policy-relevant background (PRB) for ozone over North America is ppbv, lower than currently assumed for risk assessment (40 ppbv) and resulting in underestimate of ozone risk increment from U.S. pollution [Fiore et al., 2003] Observations of elevated ozone (50-80 ppbv) at remote U.S. sites, used to challenge the PRB, are in fact explainable by regional pollution [Fiore et al., 2003]

NOAA/ITCT-2K2 AIRCRAFT CAMPAIGN IN APRIL-MAY 2002 Monterey, CA High-ozone Asian pollution plumes observed in lower free troposphere but not at surface (Trinidad Head); strong stratospheric influence (Trinidad Head sondes) CO O3O3 PAN HNO 3 May 5 plume at 6 km: High CO and PAN, no O 3 enhancement May 17 subsiding plume at 2.5 km: High CO and O 3, PAN  NO x  HNO 3 Hudman et al. [2004] Observations by D. Parrish, J. Roberts, T. Ryesrson (NOAA/AL)

CONCEPTUAL PICTURE OF OZONE PRODUCTION IN TRANSPACIFIC ASIAN POLLUTION PLUMES NO x HNO 3 PAN Asian boundary layer (OPE ~ 5) PAN, weak  O 3 Warm conveyor belt; 5-10% export of NO y mainly as PAN strong  O 3 Subsidence Over E Pacific OPE PAN  NO x  HNO 3 U.S. boundary layer very weak  O 3 10x dilution (Asian dust data) E. Asia Pacific United States Hudman et al. [2004] Stratospheric downwelling GEOS-CHEM ozone production efficiency (2-4 km)

SURFACE OZONE AT TRINIDAD HEAD, CALIFORNIA DURING ITCT-2K2 May 17 Neither observations nor models show much variability; Asian pollution enhancement (6 ± 2 ppbv in GEOS-CHEM) is undetectable Goldstein et al. [2004]

CALIFORNIA MOUNTAIN SITES ARE PARTICULARLY SENSITIVE TO ASIAN OZONE POLLUTION 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 NAAQS exceedances; unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions! May 17 obs. Asian plume event in red Hudman et al. [2004]

ASIAN POLLUTION INFLUENCE DURING ICARTT AIRCRAFT CAMPAIGN (Jul-Aug 2004) AIRS CO Column July 18 th GEOS-CHEM CO Column July 18 th Asian pollution U.S. pollution Alaskan fires Wallace McMillan (UMBC)Solene Turquety (Harvard)

ASIAN POLLUTION PLUME OFF CALIFORNIA sampled by NASA aircraft on July 1, 2004 GEOS forecast Asian CO (9 km)AIRS satellite CO data Asian pollution S. Pawson (NASA), W. McMillan (UMBC), M/ Avery (NASA), S.Turquety (Harvard). L. Jaegle (UW)

ASIAN POLLUTION PLUME OVER EASTERN U.S. sampled by NASA aircraft on July 15GEOS forecast Asian CO (9 km) Observed  O 3 = ppbv,  CO = 20 ppbv GEOS-CHEM  O 3 = 5-10 ppbv,  CO = ppbv High Halon-1211 in plume confirms Asian origin

INTERCONTINENTAL POLLUTION INFLUENCE ON AEROSOLS: SUMMARY OF PREVIOUS WORK AT HARVARD Mean Asian pollution enhancements for aerosols in U.S. surface air are 0.1  g m -3 for sulfate, less for ammonium or OC (scavenging during outflow), negative for nitrate (compensation for sulfate) [Park et al., 2003, 2004a] This pollution enhancement prevents achievability of the EPA Regional Haze Rule (natural visibility in U.S. national parks by 2064) and has important implications for the schedule of emission reductions under Phase I implemntation of the Rule ( ) [Park et al., 2004a]

DUST STORMS PROVIDE VISIBLE EVIDENCE OF INTERCONTINENTAL TRANSPORT OF AEROSOLS Glen Canyon, AZ Clear dayApril 16, 2001: Asian dust! …and anthropogenic pollution is transported together with the dust Colette Heald et al. (Harvard) satellite data

ASIAN PM POLLUTION INFLUENCE OVER WESTERN U.S. - * - AERONET __GEOS-CHEM __ Asian SO 4 +NH 4 +Nit __ Asian Dust Spring 2001 What about in surface air? Observations at clean western U.S. sites indicate Asian sulfate influence up to 2.2  g m -3 (24-h average) [Jaffe et al., 2003] AERONET aerosol optical depth (AOD) measurements at Missoula, MT Colette Heald et al. (Harvard) AOD

VISIBILITY DEGRADATION STATISTICS IN THE UNITED STATES (2001): IMPROVE vs. GEOS-CHEM Visibility decrease (deciviews: dv = 10ln(b ext /10) ) from sulfate, nitrate, and carbonaceous aerosols R.J. Park (Harvard)

FREQUENCY DISTRIBUTION OF DAILY VISIBILITY DEGRADATION (2001): IMPROVE SITE OBSERVATIONS vs. MODEL IMPROVE (EAST) MEAN > 18STD > 5 MEAN > 18 STD < 5 IMPROVE vs. MODEL REGION 1 REGION 2 MEAN < 9STD < 3.5 REGION 4 IMPROVE (WEST) Successful simulation of low end of pdf increases confidence in ability of model to describe natural (and transboundary?) signatures R.J. Park (Harvard)

SCAVENGING OF BLACK CARBON (BC) AEROSOL IN CONTINENTAL OUTFLOW TRACE-P aircraft observations off Asian Pacific Rim (Mar-Apr 2001) fine nitrate BC fine sulfate Decrease of BC concentrations with altitude parallels that of soluble species; suggests efficient scavenging Park et al. [2004b] P3B DATA over NW Pacific (30 – 45 o N, 120 – 140 o E)

Export efficiency Normalized export efficiency computed from enhancement ratios relative to CO in continental outflow plumes, normalized to emission ratio from East Asia High apparent export efficiency for BC could reflect underestimate of emissions Park et al. [2004b] EXPORT EFFICIENCIES OF BC, SO x, AND HNO 3 T

P3B DATA over NW Pacific (30 – 45 o N, 120 – 140 o E) GEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONS BC emissions from Bond et al. [2004] BC emitted as hydrophobic, becomes hydrophillic on time scale  =1 day Model underestimates BC observations by factor of 2; insufficient emissions or excessive scavenging? Park et al. [2004b]

Simulation with  = 1±1 days provides the best fit to the TRACE-P observations;  implies factor of 2 underestimate in Bond et al. [2004] inventory for East Asia  corresponding mean atmospheric lifetime of BC is 6 ± 2 days, 50% longer than for sulfate SENSITIVITY OF BC NORMALIZED EXPORT EFFICIENCY TO AGING TIME SCALE  Park et al. [2004b]