Field-Based Analysis of Chlorinated Volatile Organic Halocarbons
REGIONAL/GLOBAL INTERACTIONS IN ATMOSPHERIC CHEMISTRY Greenhouse gases Halocarbons Ozone Aerosols...
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Transcript of REGIONAL/GLOBAL INTERACTIONS IN ATMOSPHERIC CHEMISTRY Greenhouse gases Halocarbons Ozone Aerosols...
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REGIONAL/GLOBAL INTERACTIONS IN ATMOSPHERIC CHEMISTRY
Greenhouse gasesHalocarbonsOzoneAerosolsAcidsNutrients ToxicsSOURCE CONTINENT
REGIONAL ISSUES: - Surface air quality - Ecosystems
GLOBAL ISSUES: - Climate change - Ozone layer - Oxidizing power
GLOBAL ATMOSPHERE
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TROPOSPHERIC OZONE AND AEROSOLS MAKE LARGE AND INHOMOGENEOUS CONTRIBUTIONS TO RADIATIVE FORCING
IPCC 2001 contribution from Harvard/GISS/Caltech/UCI unifiedaerosol-chemistry-climate model (CACTUS)
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1800-2000 radiative forcing from tropospheric ozoneis less well constrained than implied by IPCC 2001 report
Standard preindustrial simulation:
F = 0.44 W m-2
“Adjusted” preindustrial simulation(lightning and soil NOx decreased,biogenic hydrocarbons increased):
F = 0.80 W m-2
[Mickley et al., 2001]
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Ozone+sulfate radiative forcings, 1800-2000(CACTUS model)
Yearly mean values [Mickley et al., 1999]
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INTERCONTINENTAL INFLUENCE ON SURFACE OZONE:How much does it contribute to ozone pollution?
NOx
Hydrocarbons Ozone
PAN
Boundary layer(0-2.5 km)
Free tropospherelightningNOx
Stratosphere Ozone
NOx
Hydrocarbons Ozone
PAN Chemical lossDeposition
CONTINENT 1 CONTINENT 2OCEAN
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Ozone in U.S. surface air in summer includes a 20-40 ppbv background produced outside the U.S. boundary layer
Regional pollution coordinate
OzoneBackground(“clean air”)
Ozone vs. total nitrogen oxides (NOy) at eastern U.S. sites [Trainer et al., 1993]
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Historical records imply a large anthropogenic contribution to the present-day ozone background
Ozone trend at European mountain sites, 1870-1990 [Marenco et al., 1994]
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8-h daily maximum ozone probability distribution at rural U.S. sites[Lin et al., 2000]
AIRS data statistics suggest that background ozone in U.S.has increased by ~3 ppbv over past 20 years
1980-1984 1994-1998
1980-1984
1994-1998
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The present ozone background is a sizable increment towards violation of air quality standards
0 20 40 60 80 100 120 ppbv
AOT40(seasonal)
NAAQS(8-h avg.)
NAAQS(1-h avg.)
preindustrial presentbackground
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Growth of Asian emissions over next decades will increase role of background for ozone air quality in U.S.
109 atoms N cm-2 s-1
AnthropogenicNOx emissions[IPCC, 2001]
2000
2020“Optimistic” IPCCscenario:OECD, U.S. down 20%Asia up 50%
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Modeled increase in U.S. surface ozone (ppbv) from tripling of Asian emissions (1985 to 2015)
with other emissions held constant [Jacob et al., 1999]
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Rising Asian emissions could offset the benefit of domestic emission controls
Modeled surface ozone change (ppbv) in July for 25% reduction of U.S. NOx and hydrocarbon emissions
with constant Asian emissions (1985) with tripled Asian emissions
Jacob et al. [1999]
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Increase in surface ozone from transatlantic transport of N. American and European pollution
[Li et al., 2001]
N.American influenceon Europe
European influenceon N. America
GEOS-CHEM model results, July 1997
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GEOS-CHEM: latest generation of global 3-D models of atmospheric chemistry at Harvard
• 1ox1o- 4ox5o horizontal resolution, 20-48 layers in vertical• Assimilated meteorological data from NASA/GEOS, 1988-2001• Recent/current applications:
– Tropospheric ozone : global budget, Asian outflow, U.S., Middle East, N Atlantic, tropics, interannual variability, trends
– Stratospheric ozone: coupling with troposphere– Carbon monoxide: global and regional budgets, interannual
variability– Organics: hydrocarbons, acetone, HCN, CH3I– Aerosols: radionuclides, sulfate, soot, dust, organics
(collaborations with NASA/GSFC, Duke, U. Washington) – Satellite retrievals: formaldehyde, NO2, CO, ozone– Chemical forecasts: TRACE-P, NOAA 2002
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APPLICATION OF GEOS-CHEM TO THE ORIGIN OF BACKGROUND OZONE IN U.S. IN SUMMER 1995
[Fiore et al., 2001]
• NASA/GEOS assimilated meteorological data for 1995 • 2ox2.5o horizontal resolution, 26 vertical layers• 120 chemical species (O3-NOx-hydrocarbon chemistry);
aerosol effects on chemistry, radiation • SAMI July 1995 inventory for eastern U.S.
Evaluation with AIRS, SOS, NARSTO-NE observations
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SUMMER 1995 AFTERNOON OZONEIN SURFACE AIR OVER THE U.S.
AIRS observations
GEOS-CHEM(r2 = 0.4, bias=3 ppbv)
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FREQUENCY DISTRIBUTION OF SURFACE p.m. O3
IN WESTERN MASSACHUSETTS IN SUMMER 1995
Observations(squares, triangles)
Model(crosses) Air quality
standard
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MEAN AFTERNOON OZONE BACKGROUNDIN MODEL, SUMMER 1995
Background is tagged as ozone produced outside the N. American boundary layer (surface-700 hPa)
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OZONE BACKGROUND IS DEPLETED DURING REGIONAL POLLUTION EPISODES
(due to stagnation, short O3 lifetime)
Background(clean conditions)
O3 vs. (NOy-NOx) At Harvard Forest, Massachusetts
Background(pollution episodes)
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FREQUENCY DISTRIBUTION OF AFTERNOON BACKGROUND OZONE CONCENTRATIONS
IN U.S. SURFACE AIR IN SUMMER 1995 (model)summer ensemble vs. pollution episodes
Convection upwindoccasionally results inhigh background during pollution episodes
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Convection upwind can result in high background contributions to ozone pollution episodes
Time, days0 1 2 3
Subsidence inversion
Boundarylayer
Free troposphere
Ozonedowndraft
fast ozoneproduction
> 50 ppbv day-1
Convectivecloud
Ozone pollutionepisode
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ASIAN/EUROPEAN POLLUTION ENHANCEMENTOF BACKGROUND OZONE IN U.S.
Mean model values, summer 1995 (4ox5o resolution)
“Natural” background(no anthropogenicemissions of NOx
or NMHCs anywhere,but present-day CH4)
Asian/Europeananthropogenicenhancement abovenatural background (no anthropogenicemissions in North America)
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RANGE OF ASIAN/EUROPEAN POLLUTION OZONE ENHANCEMENTS OVER THE UNITED STATES
ensemble of model results, summer 1995
Max enhancements(up to 14 ppbv)under moderatelypolluted conditions(50-70 ppbv O3)associated with recent convection
MAJOR CONCERNIF OZONE STANDARDWERE TO DECREASETO 40 or 60 PPBV
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CONCLUSIONS
• Surface ozone in U.S. in summer includes a 20-40 ppbv background originating from outside North America
• Present-day Asian emissions enhance this background by 3-7 ppbv (up to 14 ppbv)
• Asian influence on surface ozone in U.S. is highest under moderately polluted conditions (50-70 ppbv), less during acute pollution episodes (> 80 ppbv) or clean conditions
(< 40 ppbv)
• Importance of background will increase in the future due to rise in Asian emissions, lower metrics for ozone standard.
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FUTURE WORK• EPA/Harvard modeling collaboration
– Examine ozone perturbations from intercontinental transport for future scenarios and sensitivity studies
– Examine intercontinental transport of aerosols, ozone-aerosols coupling– Couple Models-3 and GEOS-CHEM to extend the nested-model capability of
Models-3 to the global scale.
• Analysis of aircraft data directed at intercontinental transport: – TRACE-P, spring 2001 (Asian outflow)– NOAA/ITCT, spring 2002 (North American inflow)– INTEX/NA, summer 2004 (North American outflow/inflow)
• Assimilation of satellite observations into global models– Use global mapping capabilities from satellites to test model simulations of
intercontinental transport for CO, ozone, aerosols