regional/global interactions in atmospheric chemistry greenhouse gases halocarbons ozone aerosols...
DESCRIPTION
TROPOSPHERIC OZONE AND AEROSOLS MAKE LARGE AND INHOMOGENEOUS CONTRIBUTIONS TO RADIATIVE FORCING IPCC 2001 contribution from Harvard/GISS/Caltech/UCI unified aerosol-chemistry-climate model (CACTUS)TRANSCRIPT
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
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)
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]
Ozone+sulfate radiative forcings, 1800-2000(CACTUS model)
Yearly mean values [Mickley et al., 1999]
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
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]
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]
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
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
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%
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]
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]
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
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
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
SUMMER 1995 AFTERNOON OZONEIN SURFACE AIR OVER THE U.S.
AIRS observations
GEOS-CHEM(r2 = 0.4, bias=3 ppbv)
FREQUENCY DISTRIBUTION OF SURFACE p.m. O3
IN WESTERN MASSACHUSETTS IN SUMMER 1995
Observations(squares, triangles)
Model(crosses) Air quality
standard
MEAN AFTERNOON OZONE BACKGROUNDIN MODEL, SUMMER 1995
Background is tagged as ozone produced outside the N. American boundary layer (surface-700 hPa)
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)
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
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
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)
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
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.
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