金沙江中下游流域面雨量特征分析

利用2000~2012年金沙江中下游流域56个国家气象观测站逐日08~08时降水资料，采用算术平均法计算得到金沙江中下游5个子流域逐日面雨量，对金沙江中下游及5个子流域面雨量的时空分布特征进行了分析，重点分析了强降水日面雨量的季节分布、频次分布、等级分布、极值分布等统计特征。结果表明:金沙江中下游降水的时空变化特征明显，年平均面雨量为812 mm，夏季降水最多，秋季次之，冬季最少，且秋雨多于春雨；5~10月为降雨集中期，降水总量占年平均降水的91%；5个子流域平均每年出现日面雨量≥20 mm的强降水29.5次，且夏季最多，秋季次之；华弹 屏山段出现强降水的频次最高，横江流域次之，雅砻江下游最少，但横江流域最易出现强降水极大值；华弹 屏山和横江流域同时发生强降水的频率最高，占流域性强降水总次数的521%，在开展金沙江中下游流域面雨量预报时要特别加以关注

ANALYSIS ON CHARACTERISTICS OF AREAL PRECIPITATION IN THE MIDDLE AND LOWER REACHES OF THE JINSHA RIVER BASIN

Using the daily 08-08 precipitation data of 56 national weather stations in the middle and lower reaches of the Jinsha River Basin from 2000 to 2012, the daily areal rainfall of the five sub basins is calculated by an arithmetic average method. The spatial and temporal characteristics of the areal rainfall in the middle and lower reaches of the Jinsha River basin and its five sub basins were analyzed, focusing on the analysis of the statistic characteristics such as seasonal distribution, frequency distribution, grade distribution, extreme value distribution of the days of heavy daily area rainfall. The results show a great temporal spatial variation of precipitation in the middle and lower reaches of the Jinsha River basin. The annual areal rainfall varied between 600 and 980 mm and averaged 812 mm. The highest annual average areal rainfall was found in Huatan Pingshan sub basin (876 mm) and the lowest value was found in the sub basin of the lower reaches of the Yalong River (723 mm). The precipitation peaked in summer, followed by autumn, spring and winter. The precipitation was concentrated from May to October, contributing 91% to the total. The frequency of heavy precipitation shows obvious seasonality: highest in summer followed by autumn and zero was found in winter. Days with heavy precipitation of above 20 mm in the five river sub basins in thirteen years was 383 in total, averaged 29.5 days per year. The frequency of heavy precipitation was at most in Huatan Pingshan sub basin, followed by Hengjiang River sub basin and the lowest was found in the sub basin of the lower reaches of the Yalong River. The heavy precipitation was concentrated from June to September, with a total of 340 mm, accounting for 88.8% of the whole year. The heavy precipitation between 30 mm and 50 mm was concentrated on the Huatan Pingshan and Hengjiang River sub basins, and heavy precipitation exceeding 50 mm was concentrated on the Hengjiang River sub basin. The monthly maximum of Hengjiang River sub basin was greater than else and the sub basin of the lower reaches of the Yalong River was significantly smaller than else in the period of heavy precipitation. The highest frequency of simultaneous heavy precipitation was found in Huatan Pingshan and Hengjiang River sub basin, counting for 52.1% of the total. This phenomenon should receive attention for areal rainfall forecast