ALADIN/HR: TESTING THE NEW SUB-GRID SCALE OROGRAPHY REPRESENTATION ON BURA CASES

Abstract: Especially important for the coastal area of Croatia is the wind forecast, particularly during the bura windstorm episodes. Current operational version of ALADIN model is rather satisfactory for the wind field forecast, although in many cases the wind speed is somewhat overestimated. A modified sub-grid scale orography representation was introduced and tested. The envelope was removed and to compensate for the loss of volume, changes in gravity wave drag parametrisation were introduced. New orography representation resulted in slight enhancement of upstream and general decrease of downstream wind speed, as well as reduction of mountain wave amplitude