MODELING TRANSPORT OF OZONE AND FINE PARTICLES MODELING TRANSPORT OF OZONE AND FINE PARTICLES TO AND FROM NORTH AMERICATO AND FROM NORTH AMERICA
Daniel J. JacobHarvard University
with Arlene M. Fiore, Rokjin Park, Colette L. Heald
and support from EPA (ICAP), EPRI, NOAA
TWO MODES OF INTERCONTINENTAL INFLUENCETWO MODES OF INTERCONTINENTAL INFLUENCE
Asia N. America Europe
Boundary layer
Free troposphere
lifting subsidence
boundary layer advection
Tropopause
HEMISPHERIC POLLUTION BACKGROUND
“Direct”intercontinental
transport
Mixing
• Direct intercontinental transport: fast (~1 week) transport from source to receptor continent; either by boundary layer advection or by lifting to lower free troposphere followed by subsidence
• Hemispheric pollution: pollution mixes in free troposphere, affecting free tropospheric background, in turn affecting surface concentrations by subsidence
2 km
MECHANISM FOR TRANSPACIFIC TRANSPORTMECHANISM FOR TRANSPACIFIC TRANSPORTOF ANTHROPOGENIC OZONE AND FINE PARTICLESOF ANTHROPOGENIC OZONE AND FINE PARTICLES
entrainment, dilution
ASIA PACIFIC NORTH AMERICA
NOx, SO2, VOC
warm conveyor
belts,convection
aerosols,HNO3
PAN (~10%)
VOCs (long-lived)
SOx (~10%)
OCaerosol PAN
O3
NOxO3sulfate
Boundary layer
Free troposphere2 km
subsidence
ozone, sulfate, OC
HEMISPHERIC POLLUTION
USING GLOBAL CHEMICAL TRANSPORT MODELS USING GLOBAL CHEMICAL TRANSPORT MODELS TO QUANTIFY INTERCONTINENTAL INFLUENCETO QUANTIFY INTERCONTINENTAL INFLUENCE
(1) Standard simulation; compare w/ observations
(2) Set N. American anthropogenic emissions to zero estimate background
(3) Set global anthropogenic emissions to zero estimate natural background
Difference between (1) and (2) regional pollution
Difference between (2) and (3) intercontinental pollution
GEOS-Chem model :• driven by NASA/GEOS assimilated meteorological data• horizontal resolution 2ox2.5o, 48 vertical levels• coupled ozone-PM simulation• used by 20 research groups in Europe and N. America (~100 publications)• extensive evaluation with U.S. observations for ozone [Fiore et al., 2002, 2003ab] and PM [Park et al., 2003, 2004]
Surface ozone at Voyageurs National Surface ozone at Voyageurs National Park, Minnesota (May-June 2001)Park, Minnesota (May-June 2001)
CASTNet observationsModelBackgroundNaturalStratospheric
+
*
Intercontinentalpollution
Regionalpollution}
}
Background: 15-36 ppbvNatural : 9-23 ppbvStratosphere: < 7 ppbv
X
Fiore et al. [2003]
Surface ozone at Yellowstone Surface ozone at Yellowstone National Park, Wyoming, National Park, Wyoming, 2.5 km altitude2.5 km altitude (March-May 2001) (March-May 2001)
CASTNet observationsModelBackgroundNatural O3 levelStratospheric
+
*
Intercontinentalpollution
Regionalpollution}
}X
Background: 30-50 ppbvNatural : 15-30 ppbv
Fiore et al. [2003]
Probability distribution of afternoon (1-5 p.m. mean) surface ozone at U.S. Probability distribution of afternoon (1-5 p.m. mean) surface ozone at U.S. CASTNet sites in March-October 2001CASTNet sites in March-October 2001
Pro
bab
ilit
y. p
pb
v-1
CASTNet observations
GEOS-Chem at CASTNet
Natural 18±5 ppbvGEOS-Chem
background 26±7 ppbvGEOS-Chem
background 29±9 ppbv MOZART-2
Intercontinental pollution enhances background by 8 ± 4 ppbv relative to natural
Fiore et al. [2003]
Ozone, ppbv
RegionalPollution
Ozo
ne
(pp
bv
)
Cumulative Probability
Low-elevation CASTNet sites, Jun-Aug
CASTNet observationsGEOS-Chem modelModel background
*
DEPLETION OF OZONE BACKGROUND DURING DEPLETION OF OZONE BACKGROUND DURING REGIONAL POLLUTION EPISODESREGIONAL POLLUTION EPISODES
Background (and intercontinental pollution influence) are highest when ozone concentrations are in mid-range (40-70 ppbv), reflecting subsidence conditions
Fiore et al. [2003]
GLOBAL OZONE BACKGROUND:GLOBAL OZONE BACKGROUND:METHANE AND NOMETHANE AND NOxx ARE THE LIMITING PRECURSORS ARE THE LIMITING PRECURSORS
240
250
260
270
280
290
300
310
320
3301995 base case
50% methane
50% NOx
50% NMVOCs
50%NOx+NMVOCs
50% CO
50% all
natural
GEOS-Chem [Fiore et al., 2002a]
Anthropogenic methane enhances surface ozone by 4-6 ppbv worldwide
Sensitivity of global tropospheric ozone inventory (Tg) to 50% global reductionsIn anthropogenic precursor emissions
INCREASE IN FREE TROPOSPHERIC BACKGROUND OZONE INCREASE IN FREE TROPOSPHERIC BACKGROUND OZONE OVER EUROPE IN THE PAST CENTURYOVER EUROPE IN THE PAST CENTURY
Observations at mountain sites [Marenco et al., 1994]
Preindustrialmodel ranges
Simulated historical ozone levels are higher than observed: is this due to model overestimates in natural sources (lightning) or calibration errors?
OBSERVED TREND IN OZONE BACKGROUND OVER OBSERVED TREND IN OZONE BACKGROUND OVER CALIFORNIA IN SPRING SUGGESTS 10-15 ppbv INCREASECALIFORNIA IN SPRING SUGGESTS 10-15 ppbv INCREASE
OVER PAST 20 YEARSOVER PAST 20 YEARS
Trend: 0.5-0.8 ppbv yr-1
Jaffe et al. [2003]
…but this is inconsistent with models; e.g., GEOS-Chem model indicates only a 2 ppbv increase over 1980-1995 (Fiore et al., 2002b)
AN EXAMPLE OF TRANSPACIFIC TRANSPORT OF AN EXAMPLE OF TRANSPACIFIC TRANSPORT OF ASIAN AEROSOL POLLUTION AS SEEN BY MODISASIAN AEROSOL POLLUTION AS SEEN BY MODIS
Detectable sulfate pollution signal correlated with MOPITT CO
X1018 [molecules cm-2]
P3B DATA over NW Pacific (30 – 45oN, 120 – 140oE)
WET SCAVENGING OF ASIAN AEROSOLS WET SCAVENGING OF ASIAN AEROSOLS DURING LIFTING TO THE FREE TROPOSPHEREDURING LIFTING TO THE FREE TROPOSPHERE
Park et al. [2005]
TRACE-P observations over NW Pacific (Feb-Mar 2001) and GEOS-Chem simulations
Sulfate is most important exported anthropogenic aerosol in model
……BUT ELEVATED OC AEROSOL IS OBSERVED IN FREE BUT ELEVATED OC AEROSOL IS OBSERVED IN FREE TROPOSPHERIC ASIAN OUTFLOW – TROPOSPHERIC ASIAN OUTFLOW –
CONTRIBUTION TO INTERCONTINENTAL POLLUTION?CONTRIBUTION TO INTERCONTINENTAL POLLUTION?ACE-Asia aircraft observations over Japan (spring 2001)
Observed (Huebert)GEOS-Chem
• correlated with CO – but also a 1-3 g sm-3 background;• implies large secondary production of OC in free troposphere missing from present models;• OC dominates aerosol loading in free troposphere
Observed (Russell)
OC/sulfate ratio
Colette .L. Heald, Harvard
INTERCONTINENTAL TRANSPORT OF ASIAN AND INTERCONTINENTAL TRANSPORT OF ASIAN AND NORTH AMERICAN ANTHROPOGENIC SULFATENORTH AMERICAN ANTHROPOGENIC SULFATE
Annual mean values as determined from GEOS-Chem 2001 sensitivity simulations with these sources shut off
Intercontinental enhancements of anthropogenic sulfate over U.S. are of same order as interstate enhancement threshold used for regulation (0.2 g m-3) and EPA estimates of natural values (0.1-0.2 g m-3) for Regional Haze Rule
Park et al. [2004]
VERTICAL STRUCTURE OF TRANSPACIFIC TRANSPORTVERTICAL STRUCTURE OF TRANSPACIFIC TRANSPORTGEOS-Chem model results for spring 2001 (15-45oN)
C.L. Heald, Harvard
Asian CO Asian sulfate
Asia N. America Asia N. America
Asian aerosols are transported in lower free troposphere and subside over the NE Pacific; topography in western U.S. promotes contact with surface
EVIDENCE OF ASIAN SULFATE IN EVIDENCE OF ASIAN SULFATE IN IMPROVEIMPROVE NETWORK NETWORKOF AEROSOL MEASUREMENTS AT U.S. SITESOF AEROSOL MEASUREMENTS AT U.S. SITES
NW US:0.72 μgm-3
NW US:1.04 μgm-3
NW US:0.60 μgm-3
spring 2001 mean 24-h seasonal maxGEOS-Chem Asian influence
NW US:0.18 μgm-3
IMPROVEGEOS-CHEMAsian anthr(GEOS-Chem)
March 1 April 1 May 1 June 1
Time series overNW U.S. (spring 01)
IMPROVE data: spring 2001 mean days of GEOS-Chem 24-h seasonal max
1.4g m-3
C.L. Heald,Harvard
High-ozone Asian pollution plumes observed in lower free troposphere but not at surface (Trinidad Head);strong stratospheric influence (Trinidad Head sondes)
CO
O3
PAN
HNO3
May 5 plume at 6 km:High CO and PAN,no O3 enhancement
May 17 subsidingplume at 2.5 km:High CO and O3,PAN NOxHNO3
Hudman et al. [2004]
Observations by D. Parrish, J. Roberts, T. Ryesrson (NOAA/AL)
PROBING TRANSPACIFIC POLLUTION TRANSPORTPROBING TRANSPACIFIC POLLUTION TRANSPORTNOAA/ITCT-2K2 aircraft campaign, April-May 2002 NOAA/ITCT-2K2 aircraft campaign, April-May 2002
EFFECT OF NORTH AMERICAN SOURCESEFFECT OF NORTH AMERICAN SOURCESON EXCEEDANCES OF EU STANDARD (55 ppbv, 8-h av.)ON EXCEEDANCES OF EU STANDARD (55 ppbv, 8-h av.)
GEOS-CHEM modelresults, summer 1997
Number of exceedance days(out of 92)
# of exceedance days thatwould not have beenin absence of N.American anthropogenicemissions
Li et al. [2002]
AIRCRAFT OBSERVATIONS IN ASIAN WARM CONVEYOR BELT (WCB) AIRCRAFT OBSERVATIONS IN ASIAN WARM CONVEYOR BELT (WCB) OUTFLOW ILLUSTRATE SCAVENGING OF AEROSOLS OUTFLOW ILLUSTRATE SCAVENGING OF AEROSOLS
DURING LIFTING TO FREE TROPOSPHEREDURING LIFTING TO FREE TROPOSPHERE
LongitudeData from E.V. Browell
boundary layer outflow
WCB outflow
Ozone:WCBoutflow
Aerosolsscavengedfrom WCBoutflow
TRACE-P campaign out of Hong Kong and Japan, spring 2001
CALIFORNIA MOUNTAIN SITES ARE MOST SENSITIVE CALIFORNIA MOUNTAIN SITES ARE MOST SENSITIVE TO ASIAN OZONE POLLUTIONTO ASIAN OZONE POLLUTION…because there is less dilution…because there is less dilution
Observed 8-h ozone at Sequoia National Park (1800 m) in May 2002vs. corresponding simulated (GEOS-CHEM) Asian pollution ozone enhancement
Asian enhancements are 6-10 ppbvduring exceedances of standard;unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions!
Hudman et al. [2004]
Ob
serv
ed o
zon
e (p
pb
v)8-
h r
un
nin
g m
ean
Simulated Asian ozone enhancement (ppbv)8-h running mean