P1.14
On the observation and development of the urban convective boundary layer during Joint Urban 2003
Michael P. Morris, Oklahoma Climatological Survey, Norman, OK; and J. B. Basara and D. Giuliano
During the Joint Urban 2003 experiment, three 915-MHz profilers collected rapid measurements of the depth of the convective boundary layer (CBL) at sites in and around Oklahoma City, Oklahoma. The primary goal of this study was to characterize the growth and development of the CBL in an urban environment and apply this knowledge to the dispersal of airborne substances. Profiles of CBL development were created from volume scans with a dwell cycle of two minutes, allowing for nearly 700 scans per day. Thus, the high temporal and spatial resolution allowed for the investigation of subtle features in the structure and evolution of the convective boundary layer.
The structure of the boundary layer took on a more “classic” appearance at the rural sites, as upward perturbations resulting from drag on the city center dissipated before reaching far outside the city limits. In contrast, the boundary layer at the urban-influenced sites had a weaker nocturnal inversion and grew much faster than the boundary layer at corresponding rural sites.
Time-series analysis of daily mixing heights, as estimated from profiler data using the method of Cohn and Angevine (2000), and comparison to upper-level wind direction yielded a strong relationship between the wind at 850 millibars and the position of the maximum growth rate of the convective boundary layer. This relationship revealed that advection played a primary role in shifting the influence of the urban thermal anomaly downwind of the city center.
Poster Session 1, Student Conference Poster Session
Sunday, 9 January 2005, 5:30 PM-5:30 PM
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