青藏高原夏季200hPa西风变化特征及其与降水的关系

The Variation of 200hPa Westerly Wind in Summer on the Tibetan Plateau and Its Relationship to the Precipitation

为了加强高原高空西风变化及其与降水关系的研究，利用NCEP／NCAR月平均再分析资料及中国160个测站月降水资料，采用线性倾向估计、小波分析、相关分析等方法，对青藏高原夏季200hPa西风近几十年的变化特征及其与中国降水的关系进行分析。结果表明：自1948年青藏高原夏季200hPa西风整体呈现显著增强趋势；且高原西风在20世纪50年代前期偏弱，在50年代中后期开始增强，并在80年代出现近62年的最大值，90年代末高原高空西风略有减弱，但不明显；小波分析表明高原200hPa西风具有2～4a的周期，且这一周期成分在50年代及70年代末至80年代前期这两个时段比较显著；高原西风的突变分析表明在1954年发生了一次较明显的增强突变。高原夏季200hPa西风与中国降水关系的分析表明：高原西风增强时在长江流域以北的中国大部分地区降水偏多，以江淮流域、川渝地区西部和东部省界以及中国西北、东北的部分地区表现显著，长江流域以南的大部分地区降水偏少，其中华南沿海及中国西南地区西南部降水偏少更加明显，降水场与大气环流有较好的配置关系。

In order to strengthen the study on westerly wind over plateau and its relationship to the precipitation, us- ing the linear-trend estimate, wavelet and correlation analysis, the variability of the 200hPa westerly wind in summer on the Tibetan Plateau and its relationship to the precipitation in China are examined based on the the monthly NCAR/NCEP reanalysis and the precipitation data from 160 stations in China. The results reveal that： in general, 200hPa westerly wind in summer on the Tibetan Plateau shows a increasing trend since 1948. And the westerly wind was weaker in the early 1950s and began stronger from the mid-and late 1950s. And it reached the maximum of nearly 62 years in the 1980s. The upper westerly wind on the Tibetan Plateau weakened slightly in the late 1990s, but not significantly. Wavelet analysis of the 200hPa westerly wind in summer on the Tibetan Plateau indicates that it has the cycle of 2 - 4a and the cycle component is more significant in the 1950s and late 1970s to the early 80s. Mutation analysis of the 200hPa westerly wind in summer on the Tibetan Plateau shows that there was a pronounced strengthening mutation in 1954. The relationships between the 200hPa westerly wind in summer on the Tibetan Plateau and the precipitation in China is explored： when the zonal wind increase, more precipitation happen in the north of the Yangtze River Basin, especially in the Huaihe River Basin, the western and eastern boundaries of Sichuan-Chongqing region and some regions in the Northwest and Northeast of China; less precipitation happen in the south of the Yangtze River Basin, especially along the coast of Southern China and southwest of the Southwest of China. Meanwhile, relatively significant relationships are found between precipitaion and circulation.