关键词: 大渡河流域, 面雨量, 雨季转换, 强降水

Abstract: Based on the daily precipitation data of 15 meteorological stations in the Dadu River Basin during 1961-2016, the areal precipitation of the upper, middle and lower reaches of the Dadu River Basin was caculated by using arithmetic average method. And the spatial and temporal distribution characteristics of its areal precipitation were analyzed. In addition, the beginning and ending date of the rainy season in the Dadu River Basin were calculated in this article. The results are as follows: (1) The areal precipitation of the middle and upper reaches of the Dadu River Basin showed an upward trend, while that of the lower reaches showed a downward trend. The relative variability and range of annual precipitation in the lower reaches were the largest, followed by the middle and the upper reaches. The areal rainfall was maximum in the Dadu River Basin in summer, it was about 50%-60% of the annual precipitation. The monthly average areal rainfall in the Dadu River Basin was 100-200 mm from May to September, and 5-20 mm from November to the following February. The peak of areal rainfall in the Dadu River Basin from north to south was delayed about a month. (2) The beginning and ending period of the rainy season calculated by the conversion index of the rainy season was more stable than that calculated by the heavy rainfall. The lower reaches of the Dadu River Basin entered the rainy season at the earliest, followed by the middle and the upper reaches. The upper reaches of the Dadu River Basin ended the rainy season at the earliest, followed by the middle and the lower reaches. The duration of rainy season in the upper, middle and lower reaches were 172 days, 182 days and 195 days, respectively. (3) Under the condition of heavy precipitation occurring in the upper reaches of the Dadu River Basin, the probability of heavy precipitation occurring in the middle and lower reaches at the same time was very small. Nevertheless, the heavy precipitation often occurred in the middle reaches of the Dadu River Basin at the same time when heavy precipitation occurred in the lower reaches.

Key words: Dadu River Basin, areal precipitation, rainy season transition, heavy precipitation