陇东南地区短历时降水特征及其分布规律

本文使用1971-2000年的自动站逐日降水资料和2009-2010年的区域站逐时降水资料，研究了陇东南地区短历时降水的特征及其分布。研究发现4-9月是一年降水的主要时段，占到了80%以上，空间分布上从西北向东南迅速增大，离高原近的地区高低值中心较多，可能是因为高原季风和高原地形的影响更大；随持续时间的增加，峰值呈现出了反位相分布，并且振幅逐渐减弱；短历时降水无论是频数还是对降水的贡献都占了很大比例，有40.3%的降水事件属于短历时降水，甚至有部分测站短历时降水的贡献超过了90%，表明短历时降水是研究地区的一种重要降水形式；在短历时降水量构成中有19.4%的降水由短历时强降水产生，表明短历时强降水是短历时降水的重要组成部分；短历时强降水傍晚达到最大，此外还有一个次峰值是在午夜时分；用新定义的概念计算了研究地区的集中期和集中度分布，发现集中度普遍较大，基本在0.6以上，主要集中在7-8月，进一步印证了“七下八上”的主汛期。

Character and Distribution of Short-duration Precipitation in Southeast Gansu, China

In this paper, the character of the short-duration precipitation in the southeast Gansu were analyzed using hourly precipitation data in 2009-2010 and daily precipitation data during 1971-2000 in Gansu province. The main precipitation time section concentrates from April to September and precipitation during the period accounts for more than 80%. Precipitation rapidly increases from northwest to southeast in the studied area, but on the other hand, the high and low centers more than other districts on the plateau, probably caused by plateau terrain and monsoon. The short-duration precipitation have their maximum values around late-afternoon, but with the precipitation duration increase, the maximum values gradually move to early morning and the amplitude decreases. The short-duration precipitation accounts for the maximum proportion not only for frequency but also for contribution to total precipitation. The 40.3% of precipitation processes belong to short-duration precipitation even more than 90% for some stations. In a word, the short-duration precipitation is an important precipitation type. The 19.4% of short-duration precipitation is heavy precipitation, also proved that short-duration heavy precipitation is an important part of short-duration precipitation. Analysis of the diurnal variation of short-duration precipitation events shows that the frequency reaches the maximum value toward evening and the second highest value at midnight. In addition, we find that the precipitation-concentration degree is quite large, basically above the 0.6, precipitation-concentration period mostly located in July and August.