SPATIAL RAINFALL DISTRIBUTION AT A STORM EVENT IN MOUNTAINOUS REGIONS, ESTIMATED BY OROGRAPHY AND WIND DIRECTION

In this paper the orographical effect for rainfall distribution at a storm event is discussed. The main effect is represented by the ground-forced ascending current of air. A three-dimensional numerical model of the hydrostatic atmosphere, including basin orography, is used to estimate the ascending current area for any wind direction. The authors also propose a new concept named directional probability of storm event (DiPoSE). A severe storm is more likely to occur when the wind blows from a high DiPoSE direction rather than from a low DiPoSE direction. The wind direction at a storm event is determined from a DiPoSE analysis and is used in the numerical model. The calculated ascending air region is regarded as a severe rainfall area in mountainous river basins. The results are examined and compared with observations.