Springtime Airmass Transport Pathways to the US Prepared by: Rudolf B. Husar and Bret Schichtel CAPITACAPITA,Washington University, Saint Louis, Missouri Submitted to: Angela Bandemehr EPA, Office of International Affair June 26, 2000

Introduction Anthropogenic and natural pollutants generated in one country are regularly transported to other countries adding to their air quality burden. On the average, transboundary pollutants transport to the US small but favorable emission and transport conditions may cause transport episodes. This work begins to assess the transboundary transport to the US by backward airmass histories during the Spring season of This work complements the companion analysis “Modeling the Episodic Transport of Air Pollutants from Asia to North America” by Hanna et al., 1999Modeling the Episodic Transport of Air Pollutants from Asia to North America

Residence Time Analysis Backtrajectories are aggregated by counting the hours each ‘particle’ resided in a grid cell. The ‘residence time’, i.e. hours the Seattle, WA back trajectories resided over each grid cell

Airmass Transport to the West Coast Seattle, WA San Francisco, CA San Diego, CA Prob. of Airmass Traversing Asia = 0.08 Prob. of Airmass Traversing Asia = The most probable long range transport to the West Coast occurs across the Pacific from the Russian coast eastward.

Airmass Transport to the Midwest Minneapolis, MN St. Louis, MO San Antonio, TX Prob. of Airmass Traversing Asia = 0.01 Prob. of Airmass Traversing Asia = 0.02 At Minneapolis, the springtime transport is from Canada. Transport to St. Louis is mostly from the North with some southerly contribution. San Antonio, receives the transport from the Gulf of Mexico with some contributions from the Great Plains and the West Coast.

Airmass Transport to the East Coast Boston, MA Norfolk, VA Miami, FL Prob. of Airmass Traversing Asia = 0.01 The springtime transport to Boston is from Eastern Canada. Transport to Norfolk is also mostly from the North with some contribution to from the South Atlantic sates. Miami receives its air from the Caribbean with some contribution from the the Eastern US.

Transport Simulation of the April 1998 Asian Dust Event April 16, 1998 SeaWiFS imageSeaWiFS

April 20 April 21 April 22 April 23 TOMS Aerosol Index Trans- Pacific Transport April CAPITA Monte Carlo Model Blue Particles 7 km

April 24 April 25 April 26 April 27 April 28 Trans- Pacific Transport April 24-28

GOES Satellite Image and West Coast PM10 Concentration During the April 98 Asian Dust Event Regional average PM10 levels reached 65 µg/m 3 compared to typical values of µg/m 3 On April 29, the PM10 exceeded 100 µg/m 3 over parts of Washington and Oregon

IMPROVE Fine Particle Dust Concentrations April 25, 1998 April 29, 1998 May 2, 1998 On April 25, the western U.S. was virtually dust-free, but reached high concentrations by April 29. On May 2, the elevated dust concentrations moved over the Rocky Mountains and the Colorado Plateau

Fires are Seasonal Vegetation fires are important to the ecology of many terrestrial systems because they cycle many trace elements. Fires are also major sources of atmospheric trace gases and aerosols. Nowadays vegetation fires are initiated mostly by humans for land clearing, agricultural harvest clearing, savanna burning for nomadic agriculture. Over the sub-Sahara savanna region has thousands of small fires every year in the December-February season.

Central American Smoke over Eastern N. America

3D Satellite Data of the C. American Smoke

Daily Global Aerosol Modeling D. Westphal, Naval Research Lab. Currently, there is an operation global aerosol model that simulates the daily aerosol concentration On any given day, the global aerosol distribution is dominated by industrial sulfates, windblown dust and biomass smoke.

POPs Transport Issues for Future Consideration The transport pattern depend on season. Need a full year transport climatology to the US Develop new methods for quantifying and displaying 3D transport e.g. separate examination of high and low elevation transport Where do the POPs come from? Global distribution of POPs sources What is the lifetime/transport distance of POPs? 5-10 days? More? How do POPs deposit from the atmosphere? Precipitation over the US and along the transport path. Are there easily measurable a better understood surrogates for POPs? Aerosols? Ozone? Are some regions of the US particularly sensitive? Alaska?