1. Transpacific transport of anthropogenic aerosols: Integrating ground and satellite observations with models AAAR, Austin, Texas October 18, 2005 Colette Heald, Daniel Jacob, Rokjin Park, Becky Alexander, Duncan Fairlie, Allen Chu (GSFC), Robert Yantosca ASIA NORTH AMERICA

2. Clear Day TRANSPACIFIC TRANSPORT OF ASIAN AEROSOLS Most documented cases consist of transport of dust: Despite their short lifetimes, aerosols can be transported across the Pacific and can affect North American air quality standards and visibility. BUT Model simulations suggest that anthropogenic aerosols from Asia can ALSO be transported to the United States [Park et al., 2004] April 16, 2001 Visibility reduction at Glen Canyon, Arizona due to transpacific transport of Asian dust Asian contribution is comparable to “natural” standard set by EPA Haze Rule (0.12 µgm -3 )

3. CHALLENGE: OBSERVING AEROSOL COMPOSITION FROM SPACE TO QUANTITAVELY VALIDATE MODELS Carbonaceous aerosols Sulfate Dust Sea Salt Nitrate SURFACE (variable reflectance properties) What we want to validate! SATELLITE AOD Assumptions: Optical Properties Size Distributions Aerosol Distributions etc. A tough measurement to make! AEROSOL SPECIATED MASS CONCENTRATIONS SIMULATED AOD *DIFFERENT* Assumptions: Optical Properties Size Distributions etc. What we are comparing! Better basis for comparison: RADIANCE (Easan Drury, Harvard)

4. DIFFERENTIAL TRANSPORT OF AEROSOLS AND CO OBSERVED FROM SPACE March 2001 Anthropogenic plume, similar for CO and aerosols (allowing for aerosol scavenging) Biomass burning plume for CO – Not observed for aerosols

5. TRANSPACIFIC TRANSPORT (2001) GEOS-CHEM underestimates MODIS observations by factor of ~2 in Spring MODIS = MODerate resolution Imaging Spectroradiometer (launched EOS-Terra Dec 1999) GEOS-Chem = global CTM with coupled oxidant-aerosol simulation [Park et al., 2003; 2004] peak Asian dust ALSO substantial anthropogenic aerosol transport MODIS AOD GEOS-Chem AOD Sulfate AOD Dust AOD

6. WHAT CAN AERONET OBSERVATIONS TELL US? Is the model/MODIS bias primarily a model underestimate or a satellite retrieval bias? AERONET sites indicate a possible MODIS retrieval bias (not correlated with cloud cover). MODIS AERONET GEOS-CHEM

7. AN EXAMPLE OF TRANSPACIFIC TRANSPORT OF ASIAN AEROSOL POLLUTION AS SEEN BY MODIS April 25, 2001 April 26, 2001 April 27, 2001

8. TRANSPACIFIC TRANSPORT EVENTS AT SURFACE SITES Midway Island (central North Pacific) 4 transpacific events tracked at surface sites IMPROVE Sites (NW United States) IMPROVE obs GEOS-Chem GEOS-Chem (Asian)

9. IMPACT OF ASIAN SULFATE ON U.S. AIR QUALITY Asian aerosols preferentially impact ground sites in the NW US. Observations at IMPROVE sites are elevated from mean when simulated Asian influence is high Simulated Asian NW US: 0.18 μgm -3 Asian events NW US: 0.60 μgm -3 Observed NW US: 0.72 μgm -3 Observed during Asian events NW US: 1.04 μgm -3

10. PROJECTED SO x EMISSIONS IN ASIA Increasing SO x emissions from Asia will degrade North American air quality and present a further barrier to attainment of domestic air quality regulations in the United States (eg. EPA Haze Rule) courtesy: David Streets One projection suggests that emissions of SO x will more than double in China between 1995-2020 [Streets & Waldhoff, 2000]

11. ORGANIC CARBON AEROSOL: IMPLICATIONS FOR TRANSPACIFIC TRANSPORT? NORTH AMERICA ASIA High concentrations of OC aerosols measured in the FT over Asia (not captured by models) [Heald et al., 2005] Observed Simulated Asian air masses Sulfate: 0.24 µgm -3 OC: 0.53 µgm -3 Twice as much OC aerosol as sulfate observed at Crater Lake [Jaffe et al., 2005] PACIFIC