Siberian Biomass Burning Plumes Across the Pacific: Impact on Surface Air Quality in the Pacific Northwest

During the summer of 2003, we conducted ground and airborne observations of CO, O3 and aerosols in the Pacific Northwest. The airborne data is discussed by Bertschi and Jaffe. In this paper we discuss the surface data. Observations were made at the Cheeka Peak Observatory on the remote northwest tip of Washington state and we have supplemented this with data from the regional Puget Sound air quality network. In two cases we observed significant enhancements in surface CO, O3 and aerosols associated with the large Siberian biomass fires which occurred during the summer of 2003. The first episode occurred on June 2-3, 2003. During this period our aircraft observations and the NAAPS global model identified significant enhancements due to long range transport of emissions from Siberian fires and this was also seen at surface sites around the Puget Sound. In some locations the ozone enhancements were significant and may have contributed to a local air pollution episode two days later. In the second case, on August 4-5, our aircraft observations and the NAAPS global model again confirmed the presence of Siberian biomass burning emissions. This was seen at our Cheeka Peak site as a substantial elevation in CO and aerosols, but with a more modest enhancement in O3. During this period, aerosol concentrations were elevated to 10-15 ug/m3 (PM 2.5) around the Puget Sound. Our observations demonstrate that long range transport can occur during summer and that it can have a significant influence on surface air quality in the western U.S.