HR: 1340h
AN: A23A-0767    [Abstracts]
TI: Observations of Ozone in Asian Pollution Plumes in the Free Troposphere at Mt. Bachelor Observatory during Spring 2004
AU: * Weiss-Penzias, P
EM: pweiss@uwb.edu
AF: University of Washington, Bothell, 18125 Campus Wy NE, Bothell, WA 98011 United States
AU: Swartzendruber, P
EM: PSwartzendruber@uwb.edu
AF: University of Washington, Bothell, 18125 Campus Wy NE, Bothell, WA 98011 United States
AU: Jaffe, D
EM: djaffe@u.washington.edu
AF: University of Washington, Bothell, 18125 Campus Wy NE, Bothell, WA 98011 United States
AU: Bertschi, I
EM: isaacpb@u.washington.edu
AF: University of Washington, Bothell, 18125 Campus Wy NE, Bothell, WA 98011 United States
AU: Dennison, J B
EM: JDennison@uwb.edu
AF: University of Washington, Bothell, 18125 Campus Wy NE, Bothell, WA 98011 United States
AU: Prestbo, E
EM: ericp@frontiergeosciences.com
AF: Frontier Geosciences, 414 Pontius Ave N, Seattle, WA 98109 United States
AB: Measurements of trace gases, aerosols and meteorological parameters were made at a new mountaintop site in the Cascade Range of Central Oregon - Mt. Bachelor Observatory (MBO) (44oN, 121oW, 2700 m asl) from February 22 - May 19 2004. One large pollution plume originating from Asia and numerous smaller ones were observed during the campaign. These plumes consisted of enhancements in carbon monoxide (CO up to 300 ppbv), aerosol scattering (ssg up to 50 Mm-1), ozone (O3 up to 80 ppbv), and total gaseous mercury (TGM up to 2.5 ng/m3). For each species we observed much greater enhancements compared to previous observations in the marine boundary layer. In total, 227 hours of measurements (11 distinct events) were classified as significantly influenced by Asian outflow, as indicated by Hysplit kinematic back trajectories that crossed Asia within 10 days, and enhancements in CO and at least one other chemical indicator. These plumes were sampled in the free troposphere and probably not influenced by regional emissions in the Western U.S. since each event was accompanied by descending air and a drop in water vapor. The strongest episode of trans-Pacific transport arrived at MBO on April 25th after only four days of transit. This event produced very strong correlations between all chemical species (r2>0.9) and enhancement ratios that are consistent with an Asian source (e.g. DTGM/DCO). Other ratios can give information on the source characteristics and processing enroute. Some events that were identified as Asian appeared to be mixed with air of stratospheric origin, producing very weak O3/CO correlations. DTGM/DO3 was generally negative during these stratospheric events, which could be the result of gas-phase oxidation of TGM in O3-rich air. Time periods during the spring campaign that were not classified as Asian or stratospherically influenced show very weak relationships between chemical species, reflecting the complex processes that occur during transport. However, the mean CO concentration during the entire period at MBO was 167 ppbv, which is significantly higher than that seen in the marine boundary layer (147 ppbv during same period in 2002), which suggests that Asian emissions have a much greater influence on the background air in the free troposphere compared to the boundary layer. For real-time data at our field sites please the URL below:
UR: http://www.bothell.washington.edu/research/jaffegroup
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0345 Pollution--urban and regional (0305)
DE: 0365 Troposphere--composition and chemistry
DE: 0368 Troposphere--constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting