1. Siberian Biomass Burning Plumes Across the Pacific: Impact on Surface Air Quality in the Pacific Northwest Dan Jaffe, Peter Weiss-Penzias, J.B. Dennison, Isaac Bertschi and Doug Westphal Acknowledgements: Lyatt Jaeglé, UW Paul Novelli, NOAA-CMDL Roxanne Vingarzan, Environment Canada Hiroshi Tanimoto, NIES-Japan Funding: NSF and NOAA

2. Trans-Pacific transport of pollutants is well documented in spring, with occasional occurrences of O 3 to ~90 ppbv. See for example: Jaffe D.,McKendry I., Anderson T., and Price H. Six 'new' episodes of trans- Pacific transport of air pollutants. Atmos. Envir. 37, 391-404, 2003. What about other seasons? Goals for Summer 2003 campaign: Quantify “background” atmospheric composition during summer; Identify whether LRT can occur during summer; Identify role of Siberian biomass burning on PNW; Better understand connection between background atmosphere and regional air quality.

3. Summer 2003 had substantial Siberian fires, larger then 1987, 1998 or 2002 NAAPS Model Forecast for June 2, 2003 Vertical profile

4. June 2 nd, vertical profile Red line shows summer median NAAPS model and Hysplit back trajectories confirm the Siberian source.

5. GEOS-CHEM global model simulation June, July, August 2003 enhancement over climatological values 2003 emissions from the Siberian fires were much larger then climatological: 61 tg for CO 0.7 tgN for NOx CO enhancement: 15-35 ppbv O 3 enhancement: 2-6 ppbv Courtesy of Lyatt Jaeglé, UW CO O3O3

6. Are there implications on air quality? On June 2 nd, 2003 long-range transport brought elevated CO and aerosols and O 3 (>100 ppbv) to the lower troposphere of the Pacific NW. On June 1-3, elevated O 3 (50-60 ppbv) was seen at a number of surface sites around Washington state; Over the next few days, a local high-pressure system moved into the region and on June 6 th, 2003, Enumclaw, Washington had an 8-hour O 3 mixing ratio of 96 ppbv, an exceedance of the US standard. Enumclaw is a rural community about 50 km south of Seattle; Was there a contribution from long-range transport to the high surface O 3 seen on June 6 th ? To answer this, we need a surrogate for local O 3 production. We have used local temperature as this surrogate to calculate a long-range transport contribution of 15-20 ppbv.

8. Conclusions  Trans-Pacific transport of pollutants from Eurasia to North America can occur in summer;  2003 had the largest area of Russian biomass burned in recent past. During the summer of 2003, we saw evidence of LRT to the Pacific NW on 3 out of 10 of our aircraft missions, including a large episode on June 2;  On June 6 th, 2003 Enumclaw Washington had an 8- hour mean O 3 value of 96 ppbv. We calculate that long-range transport contributed 15-20 ppbv to this elevated value.