黄河流域上游降水时空结构特征

黄河兰州以上区域水资源量占黄河流域水资源的一半以上,研究黄河上游兰州以上区域降水时空结构变化具有重要意义.本文利用黄河兰州以上19个降水站点1959～1998年系列数据,采用EOF技术分析了黄河上游降水的时空结构特征与变化.结果表明:黄河上游兰州以上区域降水存在四种典型降水类型,即"全部-致型"、"南北型"、"东西型"和"相间复杂型".但第-特征向量为主导,其时间变化系数与年降水量基本一致,说明黄河流域兰州以上降水主要受青藏高原大尺度气候影响,具有降水偏多(少)一致性特征.从时间尺度上降水有减少的趋势;并伴随3、6、和¨年的周期变化,而且在1986和1991年发生突变.

The Spatial and Temporal Structure of Precipitation in the Yellow River Basin

The Yellow River Basin is located in the semi-arid and semi-humid region in China, and there is 200~600 mm annual precipitation and 58 billions annual runoff. The basin is with seriously scarce water resources in China, even less in the world.The region upwards of Lanzhou has area of 222 552 km2, with 446 mm annual precipitation, 319 mm flood season precipitation and 127 mm non-flood season precipitation. But its runoff accounts for 57.5% of the runoff in the Yellow River. So the spatial and temporal changes of water resources in the region upwards of Lanzhou should have great impacts on water resources of whole basin. It is important to research the spatial and temporal structure of precipitation in the region upwards of Lanzhou.It is known that, climatic system has some typical characteristics of multi-scales space-time, multi-hierarchy structure and non-linearity nature, and that the relationships and actions among different hierarchies are intricate. In this paper, with 1959~1998 precipitation series at 19 precipitation stations of the region upwards of Lanzhou in the Yellow River basin, the spatial and temporal structure features and changes of precipitation are analyzed with Empirical Orthogonal Function (EOF) method. The results show that: (1) there are four types precipitation structures in the region, and they are "All- Consistency", "North-South", "West-East" and "Complex type"; (2)the first eigenvector is the dominant type, and its accumulation contribution rate is 42.10%. Its time coefficient has same change as precipitation. This shows that the precipitation in the region upwards of Lanzhou is controlled by large-scale climatic system of Qing-Zang Plateau and the precipitation has more or less consistency; (3) from time scale, the precipitation has downwards change with 3, 6, and 11 year periods, with two abrupt points happening in 1986 and 1991.