利用中国气象局和黄河水利委员会近30年269个观测站的降水资料,采用光滑薄面样条插值法对黄河流域各月及年降水量进行插值,在ArcMap/ArcInfo中进行图象处理和分类,完成了1km×1km栅格降水的空间化,在此基础上分析了降水的空间分布。利用GIS软件编程实现了Mann-Kendall非参数统计法与空间化技术的结合,生成了各月及年降水在空间上随时间的变化趋势图。结果表明:27年来,流域总降水量呈下降趋势,空间上表现为北半部以增加为主,南半部以减少为主。各月间差异很大,在秋冬季节,以下降趋势为主,部分地区达到显著;春夏季节除少数月份外,大部分地区降水量有不显著的增加趋势。全年降水呈下降趋势的月份占多数,但主要集中在降水较少的秋冬季节,呈增加趋势的月份集中在雨水充沛的春夏,这种变化趋势使得降水的分布更加不平衡,表现为秋冬季的降水减少,而雨水较多的5～7月降水有微弱的增加趋势。

Surfaces of monthly mean precipitation were fitted with data from 269 observation sta-tions of recent 30 years,including stations of China Meteorological Administration and Yellow River Conservancy Commission,using the Plate Smoothing Spline interpolation method.We performed the interpolation of precipitation of 1km×1km grid by using the ArcMap/ArcInfo to generate output maps on which we further analyzed the spatial distribution of monthly and yearly precipitation.The Mann-Kendall trend test was applied to examine the trend of monthly precipi-tation in recent 27 years.The results show that there is a weak negative trend for yearly precipitation,and the decline area focuses on the south of the basin.For months of autumn and winter,the rainfall presents an apparent decline trend;but during spring and summer except April,there is an increasing trend in the recent 27 years.There are more negative trend months,but they all include autumn and winter,therefore,the yearly precipitation only has a slight decline trend.Due to different changing trends in the distributions of precipitation in each month it becomes more imbalance,with less rainfall in autumn and winter while more rainfall in May,June and July.