中文摘要：

利用1961—2010年黄河流域143个测站降水量和雨日资料，分析了黄河流域年、季降水和雨日的时空变化特征。结果表明：（1）多年平均年降水量和年雨日空间分布特征均呈北少南多。（2）年降水量和年雨日变化趋势相一致，二者均呈减少趋势，年降水量负趋势的测站数达81．8％，年雨日负趋势达88．8％，即年雨日较年降水的减少趋势更显著。（3）在季节变化方面，除冬季外，春、夏和秋季的降水量和雨日都是负趋势，特别是秋季减少最显著。四季降水量通过显著性水平检验的负趋势站数从多到少依次为秋季〉春季〉夏季〉冬季，雨日则为秋季〉夏季〉春季〉冬季。（4）流域年降水和年雨日一致突变点为1985—1986年，其降水量及雨日减少主要原因是大气环流发生了变化，1986年以前黄河流域降水和雨日偏多是由于季风较强，使水汽得到有效输送和河套西北部的风向辐合造成的，而突变后降水和雨日减少与季风偏弱、缺乏有效的水汽输送和蒙古至河套的反气旋环流有关。

英文摘要：

Based on the precipitation data of 143 stations, temporal and spatial variation characteristics of precipi- tation and rain days in the Yellow River basin during 1961 --2010 are analyzed. The results show that： （1） Multi-year average spatial distribution characteristics of annual precipitation and annual rainy days in the Yellow River Basin is less in the North and more in the South. （2）Annual precipitation and annual rainy days change trend have effective consistency in the Yellow River basin during the recent 50 years, both decreasingly. And the reduction trend of the annual rain days is more significant. The percentage of stations of annual precipitation with negative trend is 81.8%, and the percentage of stations of annual rainy days with negative trend is 88.8%. （3） About the seasonal variation in the Yellow River basin, the precipitation and rainy days in winter appear positive trend while they present negative trends in other three seasons, especially in autumn. The negative trend stations of precipitation in four seasons passing the significance test are autumn 〉 spring 〉 summer 〉 winter, and the nega- tive trend stations of rain days in four seasons passing the significance test are autumn 〉 summer 〉 spring 〉 win- ter. （4）The unanimous mutation of both annual precipitation and annual rainfall in the basin is 1985 --1986, and the decrease of precipitation and rain days mainly results from the changed atmospheric circulation. For example, the above normal precipitation and rain days in 1986 are due to the stronger monsoon which enables the effective- ly conveying of vapor and the wind convergence in the northwest. On the other hand, after the mutation, the weaker monsoon, the lack of effective moisture transport and the anticyclonic circulation in the area from the Mongolia to Hetao may result in less precipitation and rain days.