Recorded presentation12A.1
An Investigation of Mountain-Valley Circulations Based on Wind Tracer Measurements
Elford G. Astling, West Desert Test Center, Salt Lake City, UT
This paper presents the results of a field program investigating the mesoscale structure of wind and temperature fields in mountainous terrain. A Doppler lidar system and a number of portable automated weather stations were deployed along a mountain slope. The instruments enhance a network of permanent surface-based meteorological sensors that are located at mountain basin and ridge-top locations. The Doppler lidar was configured for horizontal sweeps at fixed elevation angles and vertical sweeps along a fixed azimuth angle that coincided with a line of surface measurement sensors. Analyses of remotely sensed radial velocities are combined with surface data to provide information for selected cases for a nine-day period of study. These display interactions between ambient winds over the mountain ridge top, boundary layer circulations, and terrain-forced flows. The results show the mountain-valley circulations are characterized by relatively uniform flow, except for near-surface winds, with weak subsidence during the nighttime hours for levels up to 4 km measured by the lidar system. One-minute temperature fluctuations on the order of ±3oC are observed and are associated with weak wind direction variations at the 2-m level. Daytime vertical motions measured by the lidar system display large temporal variations at 20 minute time periods and exhibit coherent structure at 100-m intervals and levels between 400 m and 4 km during the mid-afternoon hours. The afternoon circulations suggest the presence of well-developed convective boundary layer at the base of the mountain slope with thermal structures that exhibit no significant tilt with height. Recorded presentation
Session 12A, Boundary Layers in Complex Terrain III
Friday, 15 August 2008, 8:30 AM-9:30 AM, Rainbow Theatre
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