TROPOSPHERIC CHEMISTRY: FROM AIR POLLUTION TO GLOBAL CHANGE AND BACK Daniel J. Jacob

NUMBER OF PEOPLE LIVING IN U.S. COUNTIES VIOLATING THE EPA AIR QUALITY STANDARDS, 1999 EPA [2001] 124 ppbv 84 ppbv

MEAN NUMBER OF SUMMER DAYS ( ) EXCEEDING THE U.S. OZONE AIR QUALITY STANDARD (84 ppbv, 8-hour average) EPA/AIRS data [Lin et al., 2001]

TREND IN THE # SUMMER DAYS EXCEEDING 84 ppbv OZONE (8-hour average) Lin et al. [2001]

TROPOSPHERIC OZONE AND RADICAL CHEMISTRY ? ? ? FiresBiosphereHuman activity Lightning Ocean physics chemistry biology Nitrogen oxides (NO x ) CO, Hydrocarbons h Ozone (O 3 ) h, H 2 O Hydroxyl (OH) The Pacman of the atmosphere! Complex non-linear chemistry! (we won’t touch it) Tropopause (8-18 km) Stratospheric ozone

GLOBAL RADIATIVE FORCING OF CLIMATE, 1750-present IPCC [2001]

Historical records imply a large anthropogenic contribution to the present-day ozone background at northern midlatitudes Ozone trend from European mountain observations, Preindustrial ozone models } [Marenco et al.,1994]

radiative forcing from tropospheric ozone is less well constrained than implied by IPCC 2001 report Standard model: F = 0.44 W m -2 “Adjusted” model (lightning and soil NOx decreased, biogenic hydrocarbons increased): F = 0.80 W m -2 [Mickley et al., 2001] Global simulation of late 19 th century ozone observations with the GISS GCM

8-h daily maximum ozone probability distribution at rural U.S. sites [Lin et al., 2000] SURFACE OZONE IN U.S. INCLUDES A ppbv BACKGROUND THAT HAS INCREASED BY ~3 ppbv OVER THE PAST 20 YEARS

THIS OZONE BACKGROUND IS A SIZABLE INCREMENT TOWARDS VIOLATION OF U.S. AIR QUALITY STANDARDS (even more so in Europe!) ppbv Europe (seasonal) U.S. (8-h avg.) U.S. (1-h avg.) preindustrial present background Europe (8-h avg.)

Growth of Asian emissions over the next decades will increase role of background for ozone air quality in U.S atoms N cm -2 s -1 Anthropogenic NOx emissions [IPCC, 2001] “Optimistic” IPCC scenario: OECD, U.S.  20%, Asia  50%

Modeled increase in mean U.S. surface ozone (ppbv) from tripling of Asian emissions (1985 to 2015) with other emissions held constant Enough to offset the benefits of 25% reductions in domestic emissions! Jacob et al. [1999]

OZONE BACKGROUND IS DEPLETED DURING REGIONAL POLLUTION EPISODES (due to stagnation, ozone deposition and chem. loss) Background (clean conditions) O 3 vs. (NO y -NO x ) At Harvard Forest, Massachusetts Background (pollution episodes) Observed (J.W. Munger) model (GEOS-CHEM) model background Pollution coordinate Fiore et al. [2001]

RANGE OF ASIAN/EUROPEAN POLLUTION SURFACE OZONE ENHANCEMENTS OVER THE U.S. IN SUMMER determined from a simulation with these emissions shut off ensemble of model results for the U.S., summer 1995 Max enhancements (up to 14 ppbv) occur under moderately polluted conditions (50-70 ppbv ozone) MAJOR CONCERN IF OZONE STANDARD WERE TO DECREASE TO 40 or 60 PPBV Fiore et al. [2001] tropical air Subsidence of Asian pollution + local production stagnation

CONCENTRATIONS AND FLUXES OF NORTH AMERICAN OZONE IN SURFACE AIR, GEOS-CHEM MODEL (1997) Li et al. [2001] APRIL JULY L H H L

ORIGIN OF SURFACE OZONE AT BERMUDA IN SPRING Li et al. [2001] Production over U.S. is the dominant source; stratosphere contributes less than 5 ppbv ( S. Oltmans)

EFFECT OF NORTH AMERICAN SOURCES ON VIOLATION OF EUROPEAN AIR QUALITY STANDARD (55 ppbv, 8-h average) GEOS-CHEM model results, summer 1997 Number of violation days (out of 92) # of violation days that would not have been in absence of N.American emissions Li et al. [2001]

OZONE DATA AT MACE HEAD, IRELAND Observed [Symmonds] GEOS-CHEM model N.America pollution events in model Time series, Mar-Aug 1997 Model vs. observed stats, Li et al. [2001]

FORECASTING TRANSATLANTIC TRANSPORT OF NORTH AMERICAN POLLUTION TO EUROPE FROM THE NORTH ATLANTIC OSCILLATION (NAO) INDEX NAO Index North American ozone pollution enhancement At Mace Head, Ireland (GEOS-CHEM model) r = 0.57 NAO index = normalized surface P anomaly between Iceland and Azores Li et al. [2001]

SURFACE OZONE ENHANCEMENTS CAUSED BY ANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTS GEOS-CHEM model, July 1997 North America Europe Asia Li et al. [2001]

QUANTIFYING INTERCONTINENTAL TRANSPORT THROUGH INTEGRATION OF OBSERVATIONS AND MODELS 3-D CHEMICAL TRACER MODELS INTERCONTINENTAL TRANSPORT: CONCENTRATIONS AND FLUXES SATELLITE OBSERVATIONS Global and continuous but few species, low resolution AIRCRAFT OBSERVATIONS High resolution, targeted flights provide critical snapshots for model testing SURFACE OBSERVATIONS high resolution but spatially limited Source/sink inventories Assimilated meteorological data Chemical and aerosol processes

TRAnsport and Chemical Evolution over the Pacific (TRACE-P) A two-aircraft NASA mission over the western Pacific in March-April 2001 to quantify Asian chemical outflow to the Pacific and its relationship to sources: long-lived greemhouse gases ozone and precursors aerosols and precursors

CENTRAL IDEA BEHIND TRACE-P: DEVELOP AN OBSERVATIONAL STRATEGY FOR “TOP-DOWN” QUANTIFICATION OF SOURCES Can we test such “bottom-up”emission estimates using atmospheric observations? Latest China report to Energy Information Administration claims a decrease of CO 2 emissions after 1997.

TRACE-P EXECUTION Emissions -Fossil fuel -Biomass burning -Biosphere, dust Long-range transport from Europe, N. America, Africa ASIA PACIFIC P-3 Satellite data in near-real time: MOPITT TOMS SEAWIFS AVHRR LIS DC-8 3D chemical model forecasts: - ECHAM - GEOS-CHEM - Iowa/Kyushu - Meso-NH -LaRC/U. Wisconsin FLIGHT PLANNING Boundary layer chemical/aerosol processing ASIAN OUTFLOW Stratospheric intrusions PACIFIC

CARBON MONOXIDE CONCENTRATIONS IN TRACE-P High concentrations from fossil fuel combusion, biofuels, and biomass burning Biomass fires

Don Blake, UCI Symbol size  1/altitude C 2 Cl 4 CONCENTRATIONS MEASURED IN TRACE-P C 2 Cl 4 (dry cleaning) is an anthropogenic pollution tracer

CORRELATIONS BETWEEN SPECIES (here CO 2 :CO) OFFERED QUANTITATIVE INFORMATION ON SOURCES IN TRACE-P CO from G.W. Sachse CO 2 from M.A. Avery

PRELIMINARY GLOBAL (GEOS-CHEM) 3-D MODEL ANALYSIS OF TRACE-P OBSERVATIONS Mat Evans, Harvard

SATELLITE MEASUREMENTS OF TROPOSPHERIC CHEMISTRY

ATMOSPHERIC COLUMNS OF NO 2 AND FORMALDEHYDE (HCHO) MEASURED FROM GOME BY SOLAR BACKSCATTER ALLOW MAPPING OF NO x AND HYDROCARBON EMISSIONS Emission NO h (420 nm) O 3, RO 2 NO 2 HNO 3 1 day NITROGEN OXIDES (NO x )NON-METHANE HYDROCARBONS Emission NMHC OH HCHO h (340 nm) hours CO hours BOUNDARY LAYER ~ 2 km Tropospheric NO 2 column ~ E NOx Tropospheric HCHO column ~ E NMHC Deposition GOME

IMPROVED RETRIEVAL OF TROPOSPHERIC NO 2 FROM GOME (errors  in molecules cm -2 ) GOME SPECTRUM ( nm) SLANT NO 2 COLUMN TROPOSPHERIC SLANT NO 2 COLUMN TROPOSPHERIC NO 2 COLUMN Fit spectrum Remove stratospheric contribution, diffuser plate artifact Use Central Pacific GOME data with: HALOE to test strat zonal invariance PEM-Tropics, GEOS-CHEM 3-D model to treat tropospheric residual Apply AMF to convert slant column to vertical column Use radiative transfer model with: local vertical shape factors from GEOS-CHEM local cloud information from CRAG          Martin et al. [2001]

CAN WE USE GOME TO ESTIMATE NO x EMISSIONS? TEST IN U.S. WHERE GOOD A PRIORI EXISTS Comparison of GOME retrieval (July 1996) to GEOS-CHEM model fields using EPA emission inventory for NO x GOME GEOS-CHEM (EPA emissions) BIAS = +3% R = 0.79 Martin et al. [2001]

GOME RETRIEVAL OF TROPOSPHERIC NO 2 vs. GEOS-CHEM SIMULATION (July 1996) GEIA emissions scaled to 1996 Martin et al. [2001]

FORMALDEHYDE COLUMNS FROM GOME: July 1996 means BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO IN U.S. IN SUMMER Palmer et al. [2001a]

GOME DETECTS THE ISOPRENE “VOLCANO” IN THE OZARKS Palmer et al. [2001b]

DEPENDENCE OF GOME HCHO COLUMNS OVER THE OZARKS ON SURFACE AIR TEMPERATURE Temperature dependence of isoprene emission (GEIA) Palmer et al. [2001b]

MAPPING OF ISOPRENE EMISSIONS FOR JULY 1996 BY SCALING OF GOME FORMALDEHYDE COLUMNS [Palmer et al., 2001b] GEIA (IGAC inventory) BEIS2 (official EPA inventory) GOME COMPARE TO…