Evolving UnderstandingEvolving Understandingofof

Pollutant TransportPollutant TransportfromfromAsiaAsiatoto

North AmericaNorth America

Richard (Tony) VanCurenRichard (Tony) VanCurenResearch Division, California Air Resources Board

Department of Applied Science, UCDWRAP 5-23-06

TransPacific Transport to North TransPacific Transport to North America:America:

The contradiction of gas and aerosol dataThe contradiction of gas and aerosol data

MOPITT COMOPITT CO20002000

TOMS AerosolTOMS AerosolApril15-May6April15-May6

19981998

The April 1998 Asian Dust Storms:The April 1998 Asian Dust Storms: a Natural Experiment a Natural Experiment

Image after Husar, R. B. et al.,J. Geophys. Res. 106: 18,317 –18,330, 2000.

Asian Dust is Asian Dust is UbiquitousUbiquitousAround the Northeastern PacificAround the Northeastern Pacific

VanCuren & Cahill, 2002

Comparative Frequencies of Asian Dust Comparative Frequencies of Asian Dust Across North AmericaAcross North America

Asian Aerosol Chemistry Asian Aerosol Chemistry at Western Cordillera at Western Cordillera

Sampling Sites Sampling Sites

•Two Asian components:Primary - Dust & combustion

Mass correlation 0.87 (<2.5um)Secondary - Aged biomass smoke

Mass correlation 0.17 (<2.5um)

•Mean Asian aerosol fraction:75% of Fines (<2.5 m dia.)60% of Total (<10 m dia.)

Principal Components from: 1234 IMPROVE 24-hr filters March - October 1988-1999Crater Lake, OR and Mt. Lassen, CA

VanCuren, 2003

DUSTY ASIAN PLUME - 1.90AGED SMOKE & SEA SALT - 0.01

FRESH SMOKE & LOCAL DUST - 1.20

ROAD VEHICLE & DUST - 0.17AGRICULTURAL SMOKE - 0.01

SEA SALT & SOIL DUST - 0.88

DUSTY ASIAN PLUME - 2.60

AGED SMOKE & SEA SALT - 0.46

FRESH SMOKE & LOCAL DUST - 0.26

AGRICULTURAL SMOKE - 0.07SEA SALT & SOIL DUST - 0.05

Dusty Asian Plume

Siberian(?) Biomass Smoke

Aerosol Composition March – OctoberAerosol Composition March – October(Transport Season)(Transport Season)

Crater Lake / Mt. Lassen Crater Lake / Mt. Lassen

COARSECOARSE

2.9 2.9 ± 1.9 ± 1.9 g/mg/m3 3

FINEFINE3.8 ± 2.0 3.8 ± 2.0 g/m3 g/m3

CARBONACEOUSSO4=

SOIL NO3-

OTHER

Mean Asian fraction:75% of Fines (<2.5

m)60% of Total (<10 m)

ITCT-2K2 ITCT-2K2 Aerosol Aerosol SamplinSampling Sitesg Sites

Trinidad Head Trinidad Head Aerosol Aerosol

CompositionComposition Modes Modes

• Marine mode– Medium to coarse sea salt

(2-6 g/m3)– Weak sulfur (.2-.4 g/m3)

• Continental mode– Coarse Si, Fe, Ca, Al, Na, K– Strong fine sulfur (1-2

g/m3)– Mineral & reacted Na– Weak sea salt (.2-.6

g/m3)

PC1 MAXIMUM - 5/19/2002

PC1 MINIMUM - 4/22/2002

MARINE 5/19

CONTINENTAL 4/22

Back Trajectory 4/23/02 - Trinidad HeadBack Trajectory 4/23/02 - Trinidad Head

Trinidad Head, Trinity Alps, & Mauna Loa Trinidad Head, Trinity Alps, & Mauna Loa Continental Aerosols’Continental Aerosols’Al - Elemental RatiosAl - Elemental Ratios

(Holmes & Zoller, 1996)

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ITCT-2K2 Findings: 1 - Dominant ModesITCT-2K2 Findings: 1 - Dominant ModesConcordant Montane AerosolConcordant Montane Aerosol

Single dominant aerosolSingle dominant aerosolAsian origin confirmed by soil element profilesAsian origin confirmed by soil element profilesConcentration varies but continuously presentConcentration varies but continuously present

MBL Disconnects Coastal Site from Free TroposphereMBL Disconnects Coastal Site from Free TroposphereSea salt & local combustion – infrequent tropospheric mixingSea salt & local combustion – infrequent tropospheric mixing

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ITCT-2K2 Findings: 2 - Air Mass Mixing ITCT-2K2 Findings: 2 - Air Mass Mixing StateState

Soil Mixing ModelSoil Mixing Model Air Mass InfluenceAir Mass Influence

Diurnal oscillation of sourcesCoarse - strong local sources and upslope transportFine - dominated by tropospheric fumigation

ITCT-2K2 Findings: 3 - Soil Mixing StateITCT-2K2 Findings: 3 - Soil Mixing State

Asian Sources Explain “Anomalous” Asian Sources Explain “Anomalous” Regional Aerosol EventsRegional Aerosol Events

2/24/1996

Regional Aerosol Chemistry:Regional Aerosol Chemistry:Feb 21 & 24, 1996Feb 21 & 24, 1996

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2/24/96

2/21/96

Back-trajectories - 2/24/96Back-trajectories - 2/24/96

Craters of the MoonCraters of the Moon

Bryce CanyonBryce Canyon

Grand CanyonGrand Canyon

Sample Global Model ResultsSample Global Model Results

• Cameron-Smith, P. et al., (2005), Impact of Long-Range Dust Transport on Northern California in Spring 2002, Internal Report Lawrence Livermore Lab

• Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability of transpacific transport, J. Geophys. Res., 110, D23103, doi:10.1029/2005JD006261.

• Park, R. J. et al. (2004), Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United States: Implications for policy, J. Geophys. Res., 109, D15204, doi:10.1029/2003JD004473.

• Heald et al. Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States, Submitted to J. Geophys. Res.

Cameron-Smith, P. et al., (2005), Impact of Long-Range Dust Transport on Northern California in Spring 2002, Internal Report Lawrence Livermore Lab

Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability of transpacific transport, of transpacific transport, J. Geophys. Res.,J. Geophys. Res., 110, D23103, doi:10.1029/2005JD006261. 110, D23103, doi:10.1029/2005JD006261.

Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability Holzer, M., T. M. Hall, and R. B. Stull (2005), Seasonality and weather-driven variability of transpacific transport, of transpacific transport, J. Geophys. Res.,J. Geophys. Res., 110, D23103, doi:10.1029/2005JD006261. 110, D23103, doi:10.1029/2005JD006261.

Park, R. J., D. J. Jacob, B. D. Field, R. M. Yantosca, and M. Chin (2004), Natural and transboundary pollution influences on sulfate-nitrate-ammonium aerosols in the United

States: Implications for policy, J. Geophys. Res., 109, D15204, doi:10.1029/2003JD004473.

““Bulk aerosol measurements from Bulk aerosol measurements from the DC-8 aircraft indicate that 40% the DC-8 aircraft indicate that 40% of non-sea-salt sulfate (nss-SO4=) of non-sea-salt sulfate (nss-SO4=) on average was incorporated in on average was incorporated in dust particles [Jordan et al., 2003]dust particles [Jordan et al., 2003]…. ….

““The observation shows strong The observation shows strong outflow in the 0- to 5-km column. outflow in the 0- to 5-km column. The model also shows an The model also shows an enhancement in that column but is enhancement in that column but is lower than observations by up lower than observations by up to a factor of 2.to a factor of 2.

Heald et al. Transpacific transport of Asian anthropogenic aerosols and its impact on surface air quality in the United States, Submitted to J. Geophys. Res.

Concluding ThoughtsConcluding Thoughts• The coast ranges and Sierra-Cascade generally prevent

Pacific marine boundary layer air from reaching the continental interior of North America.

• TransPacific Transport is strongest in spring, but occurs year-round.

• The free troposphere “background” aerosol contains “natural” desert dust, anthropogenic dust, and combustion products from Asia: ¼ soil; ¼ SO4=; 2/5 carbonaceous aerosol.

• North-westerly winds associated with “clean air corridors” commonly carry Asian aerosols, thus the “clean 20%” in the West is significantly influenced by global pollution levels.

• At “clean” western IMPROVE sites, as much as 3/4 of PM2.5 and 2/3 of Coarse Particles may come from Asia.

• Emissions growth and control efforts in Asia may modify visibility in North America.