INTERCONTINENTAL TRANSPORT OF POLLUTION:INTERCONTINENTAL TRANSPORT OF POLLUTION:POLICY IMPLICATIONSPOLICY IMPLICATIONS

Daniel J. Jacob

NOx emissions (2000)

with Rynda Hudman, Colette Heald, Duncan Fairlie, Rokjin Park, Solene Turquety,

Arlene Fiore (now at GFDL), Qinbin Li (now at JPL)

and support from EPRI, EPA, NOAA, NASA

OZONE AND PARTICULATE MATTER (PM): OZONE AND PARTICULATE MATTER (PM): TOP TWO AIR POLLUTANTS IN THE U.S. TOP TWO AIR POLLUTANTS IN THE U.S.

# millions of people living in areas exceeding national ambient air quality standards (NAAQS) [EPA, 2002]

124 ppbv (1-hour)

84 ppbv (8-hour)

Carbon monoxide (CO)Lead

Nitrogen dioxide

Ozone (O3)

Particles < 10 m (PM10)

Particles < 2.5 m (PM2.5)

Sulfur dioxide(SO2)

Any pollutant

50 g m-3 (annual)

0 50 100 150

15 g m-3 (annual)

millions

MECHANISMS FOR INTERCONTINENTAL TRANSPORT MECHANISMS FOR INTERCONTINENTAL TRANSPORT BETWEEN NORTHERN MIDLATITUDE CONTINENTSBETWEEN NORTHERN MIDLATITUDE CONTINENTS

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

ENVIRONMENTAL IMPACTS OF ATMOSPHERIC OZONEENVIRONMENTAL IMPACTS OF ATMOSPHERIC OZONE

NOx = NO + NO2: nitrogen oxide radicalsVOC (volatile organic compounds) = light hydrocarbons and substituted organic compounds

UV shield

Greenhousegas

Primary sourceof OH radicals

Smog

GLOBAL BUDGET OF TROPOSPHERIC OZONEGLOBAL BUDGET OF TROPOSPHERIC OZONE

O3

O2 h

O3

OH HO2

h, H2O

Deposition

NO

H2O2

CO, VOC

NO2

h

STRATOSPHERE

TROPOSPHERE

8-18 km

Chem prod in troposphere

4300

1600

Chem loss in troposphere

4000

1700

Transport from stratosphere

400

400

Deposition 700

300

Tg O3 yr-1 present natural

NOx, CO, methane, nonmethane VOC (NMVOC) emissions

Ozone lifetime: ~ days in boundary layer~1 mo in free troposphere

Inventory (Tg):360 230

Limiting ozone precursors: Global - NOx and methaneRegional – NOx and NMVOCs

Mickley et al. [1999]

O3

TROPOSPHERIC OZONE BACKGROUNDTROPOSPHERIC OZONE BACKGROUND

stratosphere

Latitude over NW PacificLongitude

Chinacoast

Californiacoast

Airborne lidar observations from TRACE-P aircraft mission over N. Pacific in spring 2001 [Browell et al., 2003]

20-70 ppbv ozone background, increases with altitude and latitude

OZONE BACKGROUND IS AN IMPORTANT INCREMENT OZONE BACKGROUND IS AN IMPORTANT INCREMENT TOWARD EXCEEDANCE OF AIR QUALITY STANDARDS (AQS)TOWARD EXCEEDANCE OF AIR QUALITY STANDARDS (AQS)

0 20 40 60 80 100 120 ppbv

Europe AQS seasonal 8-h avg

U.S. AQS8-h avg.

U.S. AQS1-h avg.

Surface background at northern

midlatitudes

Japan AQS 8-h avg.

preindustrial present

OZONE BACKGROUND AT NORTHERN MID-LATITUDES OZONE BACKGROUND AT NORTHERN MID-LATITUDES HAS A LARGE ANTHROPOGENIC COMPONENTHAS A LARGE ANTHROPOGENIC COMPONENT

Observations at mountain sites in Europe [Marenco et al., 1994]

Preindustrialmodel ranges

Model overestimates of 19th century observations could reflect model errors in natural ozone sources (lightning, stratosphere)…or calibration errors in the data

GEOS-CHEMGEOS-CHEM GLOBAL 3-D MODEL GLOBAL 3-D MODELOF ATMOSPHERIC TRANSPORT AND CHEMISTRYOF ATMOSPHERIC TRANSPORT AND CHEMISTRY

• Developed by Harvard Atmospheric Chemistry Modeling Group, used by 17 research groups in N. America and Europe; ~100 publications.

http://www-as.harvard.edu/chemistry/trop/geos

• driven by GEOS assimilated meteorological observations from NASA Global Modeling and Assimilation Office (GMAO); native resolution 1ox1o

• applied to simulations of ozone, aerosols (PM), CO2, methane, mercury, hydrogen,…

• nested with EPA CMAQ regional model for studies of intercontinental transport

Results presented today are from coupled ozone-aerosol simulation with 2ox2.5o resolution, 48 vertical levels

MEAN SURFACE OZONE ENHANCEMENTS FROM ANTHROPOGENIC MEAN SURFACE OZONE ENHANCEMENTS FROM ANTHROPOGENIC

NONOxx AND NMVOC EMISSIONS IN DIFFERENT CONTINENTS AND NMVOC EMISSIONS IN DIFFERENT CONTINENTS

GEOS-CHEMmodel, July 1997

North America

Europe

Asia

Li et al. [2002]

as determined from sensitivity simulations with these sources shut off

2-6 ppbvmeanenhancementsover U.S.

Fiore et al. [2002];Li et al. [2002]

tropical air

Subsidence of Asian pollution+ local production

stagnation

RANGE OF RANGE OF INTERCONTINENTAL INTERCONTINENTAL OZONE POLLUTION OZONE POLLUTION

ENHANCEMENTSENHANCEMENTSAT SURFACE SITES AT SURFACE SITES (GEOS-CHEM model)(GEOS-CHEM model)

over U.S.

over Europe

effect is maximum for ozone concentrations in mid-range (40-70 ppbv)

EFFECT OF NORTH AMERICAN SOURCESEFFECT OF NORTH AMERICAN SOURCESON EXCEEDANCES OF EUROPEAN AIR QUALITY ON EXCEEDANCES OF EUROPEAN AIR QUALITY

STANDARD (55 ppbv, 8-h average)STANDARD (55 ppbv, 8-h average)GEOS-CHEM modelresults, summer 1997

Number of exceedance days(out of 92)

# of exceedance days thatwould not have beenin absence of N.American emissions

Li et al. [2002]

NOAA/ITCT-2K2 AIRCRAFT CAMPAIGN IN APRIL-MAY 2002 NOAA/ITCT-2K2 AIRCRAFT CAMPAIGN IN APRIL-MAY 2002 Monterey, CAMonterey, CA

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)

CONCEPTUAL PICTURE OF OZONE PRODUCTIONCONCEPTUAL PICTURE OF OZONE PRODUCTIONIN TRANSPACIFIC ASIAN POLLUTION PLUMESIN TRANSPACIFIC ASIAN POLLUTION PLUMES

NOx

HNO3

PANAsianboundarylayer(OPE ~ 5)

PAN, weak O3

Warm conveyor belt; 5-10% export of NOy mainly as PAN

strong O3

Subsidence Over E Pacific

OPE 60-80PAN NOxHNO3

U.S.boundarylayer very weak O3

10x dilution(Asian dust data)

E. Asia Pacific United States

Hudman et al. [2004]

Stratosphericdownwelling

GEOS-CHEM ozone production efficiency (2-4 km)

SURFACE OZONE AT TRINIDAD HEAD, CALIFORNIA SURFACE OZONE AT TRINIDAD HEAD, CALIFORNIA DURING ITCT-2K2DURING ITCT-2K2

May 17

Neither observations nor models show much variability; Asian pollution enhancement (6 ± 2 ppbv in GEOS-CHEM) is significant but undetectable

Goldstein et al. [2004]

CALIFORNIA MOUNTAIN SITES ARE PARTICULARLY CALIFORNIA MOUNTAIN SITES ARE PARTICULARLY SENSITIVE TO ASIAN OZONE POLLUTIONSENSITIVE TO ASIAN OZONE POLLUTION

…because there is less dilution…because there is less dilutionObserved 8-h ozone at Sequoia National Park (1800 m) in May 2002

vs. corresponding simulated (GEOS-CHEM) Asian pollution ozone enhancement

Asian enhancements are 6-10 ppbvduring NAAQS exceedances;unlike at surface sites, Asian pollution influence is not minimum under high-ozone conditions!

May 17 obs. Asian plume event in red

Hudman et al. [2004]

IMPORTANCE OF METHANE FOR THE IMPORTANCE OF METHANE FOR THE TROPOSPHERIC OZONE BACKGROUNDTROPOSPHERIC OZONE BACKGROUND

240

250

260

270

280

290

300

310

320

3301995 base case

50% methane

50% NOx

50% NMVOCs

50%NOx+NMVOCs50% CO

50% all

natural

Fiore et al., [2002b]

Sensitivity of global tropospheric ozone inventory (Tg) in GEOS-CHEM to 50% global reductions in anthropogenic emissions: NOx and methane have the greatest impacts

Anthropogenic methane causes another 4- 6 ppbv enhancement in surface ozone over U.S.

OBSERVATIONS OF INTERCONTINENTAL TRANSPORTOBSERVATIONS OF INTERCONTINENTAL TRANSPORTDURING ICARTT AIRCRAFT CAMPAIGN (Jul-Aug 2004)DURING ICARTT AIRCRAFT CAMPAIGN (Jul-Aug 2004)

AIRS satellite observations GEOS-CHEM near real time simulation

Asianpollution

U.S. pollution

Alaskan fires

Wallace McMillan (UMBC) Solene Turquety (Harvard)

Carbon monoxide (CO) columns on July 18

ASIAN POLLUTION PLUME OFF CALIFORNIAASIAN POLLUTION PLUME OFF CALIFORNIAsampled by NASA aircraft on July 1, 2004

GEOS forecast Asian CO (9 km) AIRS satellite CO data

Asianpollution

S. Pawson (NASA), W. McMillan (UMBC), M/ Avery (NASA), S.Turquety (Harvard). L. Jaegle (UW)

ASIAN POLLUTION PLUME ASIAN POLLUTION PLUME OVER EASTERN U.S.OVER EASTERN U.S.

sampled by NASA aircraft on July 15

Observed O3 = 20-40 ppbv, CO = 20 ppbvGEOS-CHEM O3 = 5-10 ppbv, CO = 10-20 ppbv

High Halon-1211 in plume confirms Asian origin

0

1

2

3

4

5

6

7

8

13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00

H-1

21

1 (

pp

tv)

0

5000

10000

15000

20000

25000

30000

35000

40000

Alt

itu

de

(ft

)

GEOS forecast Asian CO (9 km)

Observed O3 (ppbv)

Observed CO (ppbv)

POLICY-RELEVANT OZONE BACKGROUND (PRB) POLICY-RELEVANT OZONE BACKGROUND (PRB) USED FOR SETTING OF U.S. NAAQSUSED FOR SETTING OF U.S. NAAQS

NAAQS(8-h avg.)

0 20 40 60 80 ppbv

Naturalbackground

Present –daybackground at

northern midlatitudes

PRB is defined as the ozone concentration that would be present in absence of North American anthropogenic emissions

PRB used for present NAAQS

Risk increment

Frequent observations at remote U.S.sites attributed by Lefohn et al. [2001] to natural background…and used to

argue that NAAQS is unattainable

Can natural background indeed be so high as to make current standard unattainable?

Ozone time series at CASTNet sites used by Lefohn et al. [2001]Ozone time series at CASTNet sites used by Lefohn et al. [2001]

At low-elevation sites: background = 20-35 ppbv, natural = 10-25 ppbv

Fiore et al. [2003]

+

* Observations (1-5 pm average)

Background (no anthrop. emissions in N. America, present methane)

Natural (no anthrop. emissions globally, preindustrial methane)

Model: Base (2001)

Stratospheric influence

Occurrences of high valuesreflect either regional pollutionor a high-altitude site

BACKGROUND OZONE IS DEPLETED IN POLLUTION EPISODESBACKGROUND OZONE IS DEPLETED IN POLLUTION EPISODES

CASTNet sitesModelBackgroundNaturalStratospheric

+

*

Background on polluted days is 20-25 ppbv, below current PRB of 40 ppbv Current NAAQS underestimates health risks and is in fact too high

Ozo

ne

(pp

bv)

Cumulative Probability

RegionalPollution

Daily mean afternoon O3 at 58 U.S. CASTNet sites

June-July-August

Fiore et al. [2003]

ATMOSPHERIC PARTICULATE MATTER (AEROSOLS)ATMOSPHERIC PARTICULATE MATTER (AEROSOLS)

Soil dustSea salt

Aerosol: dispersed condensed matter suspended in a gasSize range: 0.001 m (molecular cluster) to 100 m (small raindrop)

SO2, NOx,NH3, VOCs

Most important components of the atmospheric aerosol:-Sulfate- nitrate-ammonium-Organic carbon (OC), elemental carbon (EC)-Soil dust-Sea salt

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, spring 2001

GEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONSGEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONS

BC underestimated by factor of 2 because emissions [Bond et al.] are too low

Park et al. [2004b]

P3B DATA over NW Pacific (30 – 45oN, 120 – 140oE)

Scavenging from Asian outflow is 80-90% efficient for sulfate and BC, ~100% for nitrate

Black carbon(BC)

DUST STORMS PROVIDE VISIBLE EVIDENCEDUST STORMS PROVIDE VISIBLE EVIDENCEOF INTERCONTINENTAL TRANSPORT OF AEROSOLS OF INTERCONTINENTAL TRANSPORT OF AEROSOLS

GlenCanyon, AZ

Clear day April 16, 2001: Asian dust!

…and anthropogenic pollution is transported together with the dust

Colette Heald et al. (Harvard)

satellite data satellite data

ASIAN AEROSOL POLLUTION INFLUENCE ASIAN AEROSOL POLLUTION INFLUENCE OVER WESTERN U.S. OVER WESTERN U.S.

-*- AERONET__GEOS-CHEM __ Asian SO4

2-+NH4++NO3

-

__ Asian dust

Spring 2001

AERONET aerosol optical depth (AOD) measurements at Missoula, MT

Colette Heald et al. (Harvard)

AO

D

MEAN ASIAN POLLUTION INFLUENCES ON SURFACE MEAN ASIAN POLLUTION INFLUENCES ON SURFACE AEROSOL CONCENTRATIONSAEROSOL CONCENTRATIONS

Annual means determined from a GEOS-CHEM 2001 sensitivity simulation with Asian anthropogenic sources shut off

Park et al. [2004a]

SO42-

NO3-

NH4+

g m-3

Enhancements are low relative to air quality standard (15 g m-3)

EPA REGIONAL HAZE RULEEPA REGIONAL HAZE RULE

Requires linear improvement in visibility over 2004-2018 at federal class I areas (large national parks) toward a 2064 natural visibility endpoint

Visibility is a logarithmic function of aerosol extinction ~50% reduction in anthropogenic emissions required by 2018, sensitive to the definition of the 2064 endpoint

deciviews: dv = 10ln(bext/10), where bext is aerosol extinction

from EPA [2001]

VISIBILITY DEGRADATION STATISTICS IN THE UNITED VISIBILITY DEGRADATION STATISTICS IN THE UNITED STATES (2001): MODEL vs. OBSERVATIONSSTATES (2001): MODEL vs. OBSERVATIONS

Visibility decrease (deciviews: dv = 10ln(bext/10) )from sulfate, nitrate, and carbonaceous aerosols

R.J. Park (Harvard)

Observations (IMPROVE network) GEOS-CHEM

EPA “NATURAL DEFAULT CONCENTRATIONS” FOR THE EPA “NATURAL DEFAULT CONCENTRATIONS” FOR THE REGIONAL HAZE RULE ARE TOO LOWREGIONAL HAZE RULE ARE TOO LOW

00.20.40.60.8

11.21.41.61.8

Sulfate OrganicCarbon

2004 baseline

EPA natural default

Natural (our work)

Background (incl.transboundarypollution)

g m

-3

Western U.S.

…and don’t allow for large enhancement from transboundary pollution

Park et al. [2004a]

IMPLICATIONS FOR EMISSION REDUCTIONS IN PHASE 1 (2004-2018)IMPLICATIONS FOR EMISSION REDUCTIONS IN PHASE 1 (2004-2018) IMPLEMENTATION OF REGIONAL HAZE RULE IMPLEMENTATION OF REGIONAL HAZE RULE

Illustrative calculation for mean western U.S. conditions, assuming linear relationship between emissions and PM concentrations, and assuming constant anthropogenic sources from foreign countries between now and 2064

Desired trend in visibility

Required % decrease of U.S. anthropogenic emissions

Phase 1

30%

48%

Park et al. [2004]

WHERE ARE ASIAN EMISSIONS HEADED?WHERE ARE ASIAN EMISSIONS HEADED?It’s anyone’s guessIt’s anyone’s guess

Past trends and future projections of Chinese SO2 emissions [Streets et al., 2002]