AAAR, Austin, Texas October 18, 2005

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

2. Visibility reduction at Glen Canyon, Arizona due to transpacific transport of Asian dust April 16, 2001 Clear Day TRANSPACIFIC TRANSPORT OF ASIAN AEROSOLS Despite their short lifetimes, aerosols can be transported across the Pacific and can affect North American air quality standards and visibility. Most documented cases consist of transport of dust: BUT Model simulations suggest that anthropogenic aerosols from Asia can ALSO be transported to the United States [Park et al., 2004] 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 Better basis for comparison: RADIANCE (Easan Drury, Harvard) A tough measurement to make! What we are comparing! SIMULATED AOD SATELLITE AOD Assumptions: Optical Properties Size Distributions Aerosol Distributions etc. *DIFFERENT* Assumptions: Optical Properties Size Distributions etc. AEROSOL SPECIATED MASS CONCENTRATIONS What we want to validate! Dust Carbonaceous aerosols Sulfate Sea Salt Nitrate SURFACE (variable reflectance properties)

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

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

6. MODIS AERONET GEOS-CHEM 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).

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

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

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

10. PROJECTED SOx EMISSIONS IN ASIA • One projection suggests that • emissions of SOx will more than • double in China between • 1995-2020 • [Streets & Waldhoff, 2000] courtesy: David Streets Increasing SOx 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)

11. 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] High concentrations of OC aerosols measured in the FT over Asia (not captured by models) [Heald et al., 2005] ORGANIC CARBON AEROSOL: IMPLICATIONS FOR TRANSPACIFIC TRANSPORT? ASIA NORTH AMERICA PACIFIC