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