FACTORS CONTROLLING TROPOSPHERIC OZONE AND ITS COUPLING FROM REGIONAL TO GLOBAL SCALES Daniel J. Jacob Harvard University with support from NASA, NOAA, EPA, EPRI

GLOBAL BUDGET OF TROPOSPHERIC OZONE Global sources and sinks, Tg O3 yr-1 (GEOS-CHEM) Chem prod in troposphere 4900 Chem loss in troposphere 4200 Transport from stratosphere 500 Deposition 1200 O2 hn O3 STRATOSPHERE 8-18 km TROPOSPHERE hn NO2 NO O3 hn, H2O OH HO2 H2O2 Deposition CO, VOC

TREND IN TROPOSPHERIC OZONE BACKGROUND AT NORTHERN MIDLATITUDES Observations from European mountain sites [Marenco et al., 1994]

THIS OZONE BACKGROUND IS A LARGE INCREMENT TOWARDS VIOLATION OF AIR QUALITY STANDARDS Europe (8-h avg.) Europe (seasonal) U.S. (8-h avg.) U.S. (1-h avg.) 0 20 40 60 80 100 120 ppbv preindustrial present background

GLOBAL TRANSPORT OF TROPOSPHERIC OZONE AROUND THE NORTHERN MIDLATITUDES POLLUTION BELT Ozonesonde and MOZAIC observations at 400 hPa, July 1997 Li et al. [2001] How does this intercontinental transport of ozone contribute to regional air quality issues?

SUMMER 1995 MEAN AFTERNOON OZONE IN SURFACE AIR Fiore et al. [2002a] AIRS observations GEOS-CHEM model (r2 = 0.4, bias=3 ppbv) “Background ozone” produced outside the North American boundary layer contributes 15-35 ppbv to mean surface air concentrations in the model

SURFACE OZONE ENHANCEMENTS OVER U. S SURFACE OZONE ENHANCEMENTS OVER U.S. IN SUMMER DUE TO ASIAN & EUROPEAN ANTHROPOGENIC EMISSIONS Global 3-D model results (GEOS-CHEM) sampled for ensemble of summer days over the U.S. tropical air Subsidence of Asian pollution + local production stagnation U.S. standard European standards Fiore et al. [2002a]

NORTH AMERICAN OZONE OUTFLOW IN SURFACE AIR (GEOS-CHEM model results for 1997) APRIL H L JULY H Li et al. [2002a]

TRANSPORT OF U.S. OZONE POLLUTION TO BERMUDA IN SPRING Observations (S. Oltmans) GEOS-CHEM model (S. Oltmans) Most of surface ozone over Bermuda in spring originates from the U.S.; stratosphere contributes less than 5 ppbv Li et al. [2002b]

OZONE AT MACE HEAD, IRELAND (Mar-Aug ’97) North American pollution events enhance ozone by 5-15 ppbv Observed [Simmonds] GEOS-CHEM model N.America pollution events in model Li et al. [2002b]

TRANSPORT OF U.S. POLLUTION TO EUROPE: CORRELATION WITH THE NAO INDEX NAO index = normalized surface P anomaly between Iceland and Azores North Atlantic Oscillation (NAO) Index North American ozone pollution enhancement At Mace Head, Ireland (GEOS-CHEM model) r = 0.57 Li et al. [2002a] Greenhouse warming a NAO index shift a change in transatlantic transport of pollution

SPRINGTIME ENHANCEMENT OF OZONE OVER ASIA DUE TO EUROPEAN ANTHROPOGENIC EMISSIONS GEOS-CHEM model results at 900 hPa, March-May 1996 Liu et al. [2002]

Fossil fuel NOx emissions Methane concentration Combined effects of future anthropogenic emission trends on U.S. ozone air quality and on global climate Ozone pollution 50% NMVOC 1995 (base) 50% CH4 50% NOx 2030 A1 2030 B1 IPCC scenario Fossil fuel NOx emissions (2020 vs. present) Global U.S. Methane concentration A1 +80% -30% +35% B1 +10% -60% +20% Fiore et al. [2002b]

NOx EMISSIONS (Tg N yr-1) TO TROPOSPHERE STRATOSPHERE 0.2 LIGHTNING 5.8 FOSSIL FUEL 23.1 SOILS 5.1 BIOMASS BURNING 5.2 BIOFUEL 2.2 AIRCRAFT 0.5

OZONE POLLUTION IN THE UNITED STATES 90th percentiles of summer afternoon (1-5 pm) surface ozone concentrations (ppbv), 1980-1995 Fiore et al. [1998]