P1.4
Boundary-layer structure observed during a high ozone episode in California
Allen B. White, CIRES/Univ. of Colorado, Boulder, Colorado; and D. C. Ruffieux and C. W. King
During the California Regional PM-10/PM-2.5 Air Quality Study (CRPAQS), the NOAA Environmental Technology Laboratory (NOAA/ETL) and other agencies deployed a network of integrated wind profilers along the coast and throughout the Central Valley of California. The Cooperative Institute for Research in Environmental Sciences (CIRES) and NOAA/ETL have developed a visualization tool that allows users to display the analyzed datasets resulting from this extended network. In this paper we use this tool to investigate the meteorological factors contributing to a period of enhanced ozone encountered during late July and early August 2000. One of the output display options from the visualization tool documents the wind fields responsible for horizontal transport. An overlay option plots boundary-layer depths that were determined by analyzing vertical profiles of radar backscatter from the wind profilers. In the center of the valley, suppressed boundary-layer heights were observed that are much lower than would be predicted given the warm boundary-layer temperatures and substantial sensible heat fluxes that occurred there. The boundary-layer heights with respect to ground level increased away from the center of the valley. We believe this was the result of weak synoptic forcing which allowed the mountain-valley circulation to dominate the flow. This circulation, which may be too weak to be detected by the wind profiler network, resulted in subsidence above the center of the valley which led to suppressed boundary-layer depths. The shallow boundary layers and stagnant flow resulting from these conditions contributed to increased surface ozone concentrations in the valley.
Poster Session 1, Posters (Plese note this session has changed to an Oral Session)
Thursday, 8 November 2001, 4:45 PM-6:00 PM
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