TRANSPORT INTERCONTINENTAL OF OZONE: LINKING AIR QUALITY AND CLIMATE ISSUES
Daniel J. Jacob
WELL-DOCUMENTED TREND IN TROPOSPHERIC OZONE BACKGROUND OVER 20th CENTURY
models seem unable to reproduce it quantitatively
Observations from European mountain sites [Marenco et al., 1994]
UNCERTAINTY IN PREINDUSTRIAL OZONE: MODELS ARE HIGHER THAN 19th CENTURY OBSERVATIONS
Radiative forcing from ozone could be much higher than given by IPCC! Global simulation of late 19th century ozone observations with the GISS GCM Standard model:
F = 0.44 W m
2
"Adjusted" model (lightning and soil NOx decreased, [Mickley et al., 2001] biogenic hydrocarbons increased):
INTERCONTINENTAL TRANSPORT OF OZONE POLLUTION:
SURFACE OZONE ENHANCEMENTS CAUSED BY ANTHROPOGENIC EMISSIONS FROM DIFFERENT CONTINENTS GEOS-CHEM model, July 1997
North America
Europe
Asia
Li et al. [2002]
OZONE BACKGROUND OVER U.S. IS GENERALLY DEPLETED DURING REGIONAL POLLUTION EPISODES
due to deposition and chemical loss under stagnant conditions O3 vs. (NOy-NOx) At Harvard Forest, Massachusetts
Observed (J.W. Munger) model (GEOS-CHEM) model background
background 2.5km N American boundary layer Clean conditions
BACKGROUND Polluted conditions
Fiore et al. [2002]
Pollution coordinate
FREQUENCY DISTRIBUTION OF AFTERNOON BACKGROUND OZONE CONCENTRATIONS IN U.S. SURFACE AIR IN SUMMER 1995 (model) summer ensemble vs. pollution episodes
Convection upwind occasionally results in high background during pollution episodes
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. Subsidence of Asian pollution + local production
tropical air
stagnation
European standards
U.S. standard
Fiore et al. [2002]
Combined effects of future anthropogenic emission trends on U.S. ozone air quality and on global climate: importance of methane!
Ozone pollution
NO x
NO
C
x
VO C
ba
0A 1 20 3
se )
CH 4
VO
CH 4
A1
B1
203 0
20 30
50 %
IPCC scenario
50 %
Fossil fuel NOx emissions (2020 vs. present) Global U.S. +80% +10% -30% -60%
Methane concentration (2020 vs. present) +35% +20%
50 %
19 9
50 %
50
A1 B1
Fiore et al. [2002]
203 0
5(
NM
50 %
NM
%
B1
NORTH AMERICAN OZONE OUTFLOW IN SURFACE AIR
Simulated concentrations and fluxes of North American pollution ozone GEOS-CHEM results for 1997
L H L H
APRIL
JULY
Li et al. [2002]
TRANSPORT OF U.S. OZONE POLLUTION TO BERMUDA IN SPRING
Observations Observations (GEOS-CHEM) from (S. Oltmans) S. Oltmans r = 0.82, bias 1.8 ppbv model source GEOS-CHEM attribution (S. Oltmans) model
Most of surface ozone over Bermuda in spring originates from the U.S. (outflow behind cold fronts); stratosphere contributes less than 5 ppbv Li et al. [2002]
OZONE PROFILE AT BERMUDA, APRIL 1996 (SEASONAL MAXIMUM)
Stratospheric source of ozone is unimportant throughout tropospheric column
Ozonesonde data (n = 28) from S. Oltmans
Li et al. [2002]
APRIL OZONE CLIMATOLOGY OVER NORTH AMERICA
Ozonesonde observations (1988-2000) GEOS-CHEM model (1996)
Model can reproduce observations without invoking stratospheric influence Li et al. [2002]
PREVIOUS ARGUMENT FOR HIGH-ALTITUDE SOURCE OF OZONE AT BERMUDA FROM TRAJECTORY ANALYSES
Oltmans and Levy [1994]: "On days with high ozone ... the trajectories all come from north of 50N and altitudes near 600 mb." Moody et al. [1995]: "High-ozone events are associated with high-speed subsident flow of North American continental origin" Moody et al. [1995]
GEOS-CHEM SIMULATION REPRODUCES ASSOCIATION OF HIGH OZONE AT BERMUDA WITH SUBSIDING TRAJECTORIES FROM NW
March 18, 1996 event: 290 K back-trajectory Subsiding air Cold front Ozone pollution NORTH AMERICA BERMUDA
Continental ozone pollution mixes with subsiding air behind cold fronts Li et al. [2002]
ANOTHER EXAMPLE: GEOS-CHEM SIMULATION OF APRIL 13, 1996 EVENT
Li et al. [2002]
GEOS-CHEM SIMULATION REPRODUCES OBSERVED CORRELATIONS OF OZONE WITH 7Be AND 210Pb AT BERMUDA AND TENERIFE (3 km)
BERMUDA + for both 7Be and 210Pb: consistent with Huang et al. [JGR 1999]
TENERIFE + for 7Be, - for consistent 210Pb: with Prospero et al. [GRL 1995] Ozone at Tenerife is mostly produced in middle troposphere Li et al. [2002]
OZONE DATA AT MACE HEAD, IRELAND: North American pollution signal is there but faint
Time series, Mar-Aug 1997 GEOS-CHEM Observed [Simmonds] model N.America pollution events in model Model vs. observed stats, 1993-1997
Li et al. [2002]
EFFECT OF NORTH AMERICAN SOURCES ON VIOLATIONS 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. [2002]
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. [2002]
Greenhouse warming
NAO index shift change in transatlantic transport of pollution
Enhancements in Asian surface ozone due to European anthropogenic emissions (GEOS-CHEM, 1996)
Liu et al. [2002]
GLOBAL MODEL ANALYSIS OF OZONESONDE OBSERVATIONS ALONG THE PACIFIC RIM (1993-1997)
Hong Kong, 1996 High UT variability at Hong Kong in winter-spring reflects alternance of tropical and stratospheric influences 300-120 hPa observations GEOS-CHEM model 700-300 hPa 850-700 hPa
Spring enhancement from SE Asian biomass burning
Liu et al. [2002]
ALTERNANCE OF TROPICAL AND STRATOSPHERIC INFLUENCES IN WINTER UT OVER HONG KONG: comparison of Dec 24, 1996 and Jan 6, 1997
Observed GEOS-CHEM
Sonde and model profiles
Model ozone concentrations and fluxes, 200 hPa
Stratospheric ozone tracer at longitude of Hong Kong Liu et al. [2002]
SUMMER UT OZONE POLLUTION EVENT OVER HONG KONG August 21, 1996
Asian pollution
Sonde and model profiles
Observed GEOS-CHEM
Model enhancement of ozone concentrations and fluxes due to Asian anthropogenic sources
Liu et al. [2002]
LARGE MODEL OVERESTIMATE OF O3 OVER S. ASIA: aerosol effects are not enough to fix it
MOZAIC aircraft observations (1995-99) GEOS-CHEM with full aerosol photochemistry
2 2 3
GEOS-CHEM w/o radiative effects or uptake of HO , NO , or NO by aerosols Martin et al. [2002]
GOME RETRIEVAL OF TROPOSPHERIC NO2 vs. GEOS-CHEM SIMULATION (July 1996)
Martin et al. [2002]
GEIA emissions scaled to 1996
CAN WE USE GOME TO ESTIMATE NOx EMISSIONS? TEST IN U.S. WHERE GOOD A PRIORI EXISTS
Comparison of GOME retrieval (July 1996) to ...