The Formation and Fate of Pollutant Layers aloft in Central California

Sharon Zhong
Pacific Northwest National Laboratory
P. O. Box 999
MSIN K9-30
Richland, WA 99352
Richland, Washington
(509) 372-6139
s.zhong@pnl.gov

Leonard Barrie
Pacific Northwest National Laboratory

Elevated layers of ozone, aerosols and their gaseous precursors are frequently observed above the atmospheric boundary layer over and downwind of major urban areas. Because the dynamical and chemical processes governing the formation and evolution of these elevated pollution layers are not yet clear, especially over areas of complex terrain, current air quality models are unable to accurately describe them and frequently underpredict their effects on ground-level oxidant concentrations. This research program is designed to use a combined data analyses and modeling approach to (1) determine the dynamical and chemical processes governing the formation and evolution of layers of high pollutant concentrations aloft in areas of complex terrain, and to (2) assess the contributions of these elevated pollution layers to surface ozone concentrations. The primary data set for the analyses is from the Central California Ozone Study (CCOS) conducted during a four-month period in the summer of 2000 in conjunction with the year-long California Regional PM₁₀/PM_2.5 Air Quality Study (CRPAQS) in California's Central Valley and adjacent airsheds. The extensive chemical and meteorological data base, collected by CCOS-CRPAQS using in sitù and remote sensing instruments and a number of research aircraft, including the Department of Energy's Gulfstream-1, has exceptionally high spatial and temporal resolution and is especially well suited for the proposed research. Our goal is to gain detailed understanding of how meteorology interacts with air chemistry to form pollution layers aloft in a region with land-ocean contrasts and complex topography and to quantify the impact of these elevated layers on surface pollutant concentrations. This knowledge can be used to improve air quality models and to help in the design of effective new pollution control strategies.

Some further information can be found in the viewgraphs from a presentation at the Atmospheric Sciences Program Annual Meeting held in February 2001.