Hydro-meteorogical studies on D-D and D-A characteristics of drought

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Reasonable employmentts of water-usements during a drought or a water shortage are required long-term precipitaton predictions. But nowadays neither a physical nor a probability model for a prediction is completed.In this study, low-precipitation occurences with characteristics based upon precipitation time series are stochastically investigated, and a statistic proposal method of the low-precipitation prediction is made. The regions being often hit by droughts have both high variences of precipitations and bimode ditributions. A meanvalue used generally, therefore, is pointed out with a thin confidence. Relations between low-precipitation magnitudes and its durations have some quantities. And a non-exceed probability of low-precipitations is clarified a depth-duration relation decreasing exponentialy with a duration. With this stochastic characteristic, a low-precititation probability prediction model is performed, and its exactness is made certain of some unusual drought examinations.The other side, a relation between a lowprecipitation magnitude and its influ-ential area is studied spatially, too. And it is shown an exponential depth-area relation, and the structure of it is revealed through the study that two coefficients in its equation mean climatic indices of a drought characteristic.