基于EOF的雅鲁藏布江流域干湿季降水变化的时空分异研究

Analyzing Spatial and Temporal Distribution of Precipitation at Wet or Dry Season in Yarlung Zangbo River Basin Using Empirical Orthogonal Function

摘要: 根据2000年~2010年雅鲁藏布江流域的15个气象站点的月值降水数据，采用经验正交函数分解法(EOF)，分别计算出雅鲁藏布江流域干湿季降水的时空分布特征和时间系数序列。结果表明：应用EOF方法可以很好地揭示降水场的时空分布特征，且对雅鲁藏布江流域而言前4种模态揭示了四种分布场，干季降水的累计贡献率达99.84%，湿季降水的累计贡献率达89.81%。雅鲁藏布江流域干湿季降水的主要空间分布特征是“东–西差异分布”，即表现出西部偏少东部偏多的特点，尤其是在喜马拉雅山脉最东端的米林宽谷地带降水最为丰富，分析其原因是季风气候和印度洋的暖湿气流对东部影响较大，西部由于海拔高，水汽很难到达，因此西部降水较东部少。

Abstract: According to the monthly precipitation data of 15 meteorological stations in the Yarlung Zangbo river basin during the period from 2000 to 2010, and using the method of empirical orthogonal function (EOF), we respectively calculated the spatial and temporal distribution characteristics of precipitation in wet and dry season and the time-coefficient series. The results showed that the EOF method was capable of revealing the spatial and temporal distributions of precipitation field for the Yarlung Zangbo river basin, with the first four EOFs reflecting the four vector distribution fields; furthermore, we can know that the cumulative contribution rate of precipitation is 99.84% at dry season and 89.81% at wet season. The main space distribution characteristic of dry or wet season precipitation is different distribution from west to east in Yarlung Zangbo river valley. It shows that the precipitation in western district is more than that in eastern district, such as Milin wide valley in the eastern end of Himalayas, which is one of most abundant precipitation areas, because it is influenced by the monsoon climate and the warm moist air flow from the eastern Indian Ocean. However, due to the high altitude, the water vapor is hard to reach the west area. So the precipitation of west area is relatively less compared to the east.