Mean Flow and Turbulence in Complex Terrain
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Atmospheric models used to describe horizontal diffusion in the surface layer depend upon a detailed characterization of the mean flow and standard deviation of wind direction fluctuations SD theta. Meteorological data were collected from 12 tower located across the coastal complex terrain of Vandenberg AFB, CA. from August 1983 to July 1984 in order to analyze these mean and turbulence parameters as a function of stability, time averaging, wind direction, wind speed, elevation and terrain. Three stability cases were chosen from Richardson Number criteria and found representative of specific flow regimes. SD theta was a function of stability with the largest values associated with the unstable sea breeze case and lower values with the stable land breezedrainage flow and neutral post-frontal cases. All three stability cases showed varying degrees of SD theta dependence on time averaging, wind direction, wind speed, elevation, and terrain with greater time averaging dependence found in the unstable case, greater wind direction and terrain dependence noted in the stable case, and greater lower level height dependence found in both the stable and unstable cases. In contrast to most findings over homogeneous terrain, SD theta dependence on wind speed was found in all three stability cases with this dependence most important in the neutral case.