近五十年我国西北地区降水强度变化特征

Characteristics of Northwest China Rainfall Intensity in Recent 50 Years

鉴于近五十年来我国西北东部降水减少、西部降水增多的现象,本文根据中国气象局信息中心提供的西北及内蒙古自治区日降水资料集,利用筛选后的西北186个测站1958～2005年的数据,对四季西北东、西部不同强度降水的降水量、降水日数、降水强度变化进行了分析。结果表明：近五十年来,中国西北地区降水以强降水为主,较强以上强度降水占总降水日数的5%,但其降水量占总降水量75%;西北东部不同强度的降水都减少,而西部只有弱降水减少,其他强度的降水都增加,且西北西部中等以上强度的降水增加较显著;弱降水的总量减少,弱降水的强度却加大,强降水强度增强,而极强降水强度却减弱;降水的日数变化是降水量变化的主要原因。

Northwest China is being wetter recently, and the precipitation shows different trend in the eastern and western regions. The latest daily rainfall data, which is provide by the Chinese Meteorological Administration Data Center, are used to analyze characteristics of the rainfall amount, rainfall days and rain intensity. In recent 50 years in Northwest China, the total rainfall is mainly contributed by the stronger rain, which contributes 75% rainfall in 5% rainfall days; the rainfall trend is greatly different in different regions, in eastern Northwest China, the rairffall has been in decreasetrend, however, in the western region, it has been in increase trend. The rainfall in weak intensity decreases, but the intensity increases. The rainfall in stronger intensity increases, and the intensity also increases except the intensity of the extreme rain storm. For all seasons, the rainfall days play an important role in contributing the rainfall amount.