Doppler Sodar Analysis of Frontal Friction in Relation to Frontal Slope

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Abstract

Doppler sodar information on the wind field in relation to frontal slope observed on reflectivity facsimile records was considered during Mesogers 84 experiment. The data have been analyzed to examine and quantify the correlation between vertical (updraft/downdraft) velocities and the frictional velocity in the surface layer. Based on theoretical considerations, the frontal slope modifications due to divergence of frontal friction have been quantified, and the associated drag coefficients are tentatively established. It has been observed that the downdraft velocities tend to increase with the horizontal wind speed in the surface layer. Frontal slope is directly proportional to the magnitude of momentum transfer (in the direction of front propagation) caused by friction velocity in the surface layer. Estimated values of drag are realistic.

Abstract

Doppler sodar information on the wind field in relation to frontal slope observed on reflectivity facsimile records was considered during Mesogers 84 experiment. The data have been analyzed to examine and quantify the correlation between vertical (updraft/downdraft) velocities and the frictional velocity in the surface layer. Based on theoretical considerations, the frontal slope modifications due to divergence of frontal friction have been quantified, and the associated drag coefficients are tentatively established. It has been observed that the downdraft velocities tend to increase with the horizontal wind speed in the surface layer. Frontal slope is directly proportional to the magnitude of momentum transfer (in the direction of front propagation) caused by friction velocity in the surface layer. Estimated values of drag are realistic.

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