ST RADAR EVALUATION OF THE STANDARD-DEVIATION OF THE AIR VERTICAL VELOCITY PERTURBED BY THE LOCAL OROGRAPHY

During several campaigns in France, the same clear-air Doppler VHF ST radar 'Provence' has been configured to explore lee wave effects on th e air vertical velocity. Very different conditions of lee wave occurre nce are related to the change of orographic conditions between the dif ferent stations and around a specific station. For each case, the stan dard deviation of the time fluctuations of the air vertical velocity i n the troposphere above the radar has been evaluated and related to th e height-range of the upstream orography. This evaluation was also mad e using results already published and obtained elsewhere by the same k ind of radars. Using 15 available cases, the standard deviation of the vertical velocity is found to be related mainly to the upstream orogr aphy height-range. This result makes possible the evaluation of the ve rtical velocity fluctuation range by the simple knowledge of the upstr eam orography in the case of lee wave occurrence. (C) 1997 Elsevier Sc ience Ltd.