INTERCONTINENTAL TRANSPORT OF OZONE AND AEROSOLSINTERCONTINENTAL TRANSPORT OF OZONE AND AEROSOLS

Daniel J. Jacob

and support from NOAA, EPRI, NASA, EPA (ICAP)

with T. Duncan Fairlie, Colette L. Heald, Rynda C. Hudman, Rokjin J. Park, Solene Turquety, Lyatt Jaegle (UW)

INTERCONTINENTAL TRANSPORT OF OZONE POLLUTION:INTERCONTINENTAL TRANSPORT OF OZONE POLLUTION:SUMMARY OF PREVIOUS WORK AT HARVARDSUMMARY OF PREVIOUS WORK AT HARVARD

• Anthropogenic NOx and NMVOC emissions outside North America enhance surface ozone over the U.S. by 2-6 ppbv on average; influence is maximum when ozone is in mid-range (40-70 ppbv) but low under stagnation conditions conducive to pollution episodes [Fiore et al., 2002a]

• Anthropogenic methane emissions increase surface ozone by another 4-6 ppbv through increase in the ozone background [Fiore et al., 2002b]

• 50% of exceedances of the (55 ppbv, 8-h avg.) air quality standard in Europe would not happen in the absence of N. American NOx and NMVOC emissions [Li et al., 2002]

• Policy-relevant background (PRB) for ozone over North America is 20-35 ppbv, lower than currently assumed for risk assessment (40 ppbv) and resulting in underestimate of ozone risk increment from U.S. pollution [Fiore et al., 2003]

• Observations of elevated ozone (50-80 ppbv) at remote U.S. sites, used to challenge the PRB, are in fact explainable by regional pollution [Fiore et al., 2003]

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 undetectable Goldstein et al. [2004]

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

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 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]

ASIAN POLLUTION INFLUENCE ASIAN POLLUTION INFLUENCE DURING ICARTT AIRCRAFT CAMPAIGN (Jul-Aug 2004)DURING ICARTT AIRCRAFT CAMPAIGN (Jul-Aug 2004)

AIRS CO Column July 18th GEOS-CHEM CO Column July 18th

Asianpollution

U.S. pollution

Alaskan fires

Wallace McMillan (UMBC) Solene Turquety (Harvard)

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 OVER EASTERN U.S.ASIAN POLLUTION PLUME OVER EASTERN U.S.sampled by NASA aircraft on July 15GEOS forecast Asian CO (9 km)

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

INTERCONTINENTAL POLLUTION INFLUENCE ON AEROSOLS:INTERCONTINENTAL POLLUTION INFLUENCE ON AEROSOLS:SUMMARY OF PREVIOUS WORK AT HARVARDSUMMARY OF PREVIOUS WORK AT HARVARD

• Mean Asian pollution enhancements for aerosols in U.S. surface air are 0.1 g m-3 for sulfate, less for ammonium or OC (scavenging during outflow), negative for nitrate (compensation for sulfate) [Park et al., 2003, 2004a]

• This pollution enhancement prevents achievability of the EPA Regional Haze Rule (natural visibility in U.S. national parks by 2064) and has important implications for the schedule of emission reductions under Phase I implemntation of the Rule (2004-2018) [Park et al., 2004a]

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

-*- AERONET__GEOS-CHEM __ Asian SO4+NH4+Nit __ Asian Dust

Spring 2001

What about in surface air? Observations at clean western U.S. sites indicate Asian sulfate influence up to 2.2 g m-3 (24-h average) [Jaffe et al., 2003]

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

Colette Heald et al. (Harvard)

AO

D

VISIBILITY DEGRADATION STATISTICS IN THE VISIBILITY DEGRADATION STATISTICS IN THE UNITED STATES (2001): IMPROVE vs. GEOS-CHEMUNITED STATES (2001): IMPROVE vs. GEOS-CHEM

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

R.J. Park (Harvard)

FREQUENCY DISTRIBUTION OF DAILY VISIBILITY DEGRADATION (2001): FREQUENCY DISTRIBUTION OF DAILY VISIBILITY DEGRADATION (2001): IMPROVE SITE OBSERVATIONS vs. MODELIMPROVE SITE OBSERVATIONS vs. MODEL

IMPROVE (EAST)

MEAN > 18 STD > 5

MEAN > 18 STD < 5

IMPROVE vs. MODELREGION 1

REGION 2

MEAN < 9 STD < 3.5

REGION 4IMPROVE (WEST)

Successful simulation of low end of pdf increases confidence in ability of modelto describe natural (and transboundary?) signatures

R.J. Park (Harvard)

SCAVENGING OF BLACK CARBON (BC) AEROSOLSCAVENGING OF BLACK CARBON (BC) AEROSOL IN CONTINENTAL OUTFLOW IN CONTINENTAL OUTFLOW

TRACE-P aircraft observations off Asian Pacific Rim (Mar-Apr 2001)

fine nitrate BC

fine sulfate

Decrease of BC concentrations with altitude parallels that of soluble species;suggests efficient scavenging Park et al. [2004b]

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

Export efficiency Normalized export efficiency

computed from enhancement ratios relative to CO in continental outflow plumes,normalized to emission ratio from East Asia

[ ]( )

[ ]CO

X

E Xf z

E CO

( )

(0)

f z

f

High apparent export efficiency for BC could reflect underestimate of emissions

Park et al. [2004b]

EXPORT EFFICIENCIES OF BC, SOEXPORT EFFICIENCIES OF BC, SOxx, AND HNO, AND HNO33TT

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

GEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONSGEOS-CHEM SIMULATION OF TRACE-P OBSERVATIONS• BC emissions from Bond et al. [2004]• BC emitted as hydrophobic, becomes hydrophillic on time scale =1 day

Model underestimates BC observations by factor of 2; insufficient emissions or excessive scavenging?

Park et al. [2004b]

Simulation with = 1±1 days provides the best fit to the TRACE-P observations; implies factor of 2 underestimate in Bond et al. [2004] inventory for East Asia corresponding mean atmospheric lifetime of BC is 6 ± 2 days, 50% longer than for sulfate

SENSITIVITY OF BC NORMALIZED EXPORT EFFICIENCY SENSITIVITY OF BC NORMALIZED EXPORT EFFICIENCY

TO AGING TIME SCALE TO AGING TIME SCALE

Park et al. [2004b]