近50多年来我国西部地区降水的时空变化特征

利用1954-2006年我国西部225个气象站的年平均降水量资料, 应用经验正交函数和旋转经验正交函数方法将我国西部分为9个降水类型, 研究了我国西部地区降水的时空变化特征. 结果表明: 南疆盆地、甘肃河西西部和内蒙古西部是我国西部降水年际间变动最大、降水最不稳定的地区, 而四川省西部地区的降水年际变动最小、降水比较稳定. 1954-2006年我国西部地区降水总体呈增加的趋势, 降水空间分布大致以100°E为界, 以西降水增加明显, 以东降水减少. 降水量显著增加的区域是南疆型, 而西北地区东部的关中型的降水减少最为显著. 1980年代中期是我国西部大部分地区降水量变化的转折期. 我国西部的降水变化主要分为5种类型, 年降水量变化存在较为显著的准8~9 a和4~5 a的周期振荡.

Temporal and Spatial Variation of Precipitation over Western China During 1954-2006

Precipitation data from 225 meteorological stations in western China from 1954 to 2006 are analyzed through the empirical orthogonal function and the rotated empirical orthogonal function. Nine precipitation subregions in western China can be divided. Among them, the subregions of southern Xinjiang, western Hexi Corridor and western Inner Mongolia have prominent change in annual precipitation. The western Sichuan subregion has minor change in annual precipitation. As a whole, precipitation in western China had increased obviously, but in east of 110°E had decreased. It is concluded that there are 5 types of precipitation changing in western China. Precipitation increased evidently in Xinjiang. It is found that there are precipitation changing periods of 8 to 9 years and 4 to 5 years.