1969~2018年西南地区夏季降水变化特征分析

Study on the Variation Characteristic of Summer Precipitation over the Southwest China in 1969-2018

利用西南地区122个台站逐月降水量资料、Hadley全球海表温度资料以及NCAR/NCEP月平均再分析资料,通过线性趋势法、EOF分析和相关分析等方法,分析了西南地区夏季降水变化特征及其原因,结果表明:近50年西南地区夏季降水气候平均值为535.1 mm,整体呈增加趋势。EOF分析表明西南地区夏季降水第一模态为南–北反向空间分布,第二模态为西南–东北反向分布,第三模态为西北–东南反向分布,且各模态时间系数均具有显著的年际和年代际变化。相关分析表明西南地区夏季降水的变化与低层冷高压、200 hPa西风急流、500 hPa西太平洋副热带高压、东北低涡、850 hPa风场等多种因素有关。此外,西南地区夏季降水还与太平洋海温存在密切联系,前期冬季中低纬东太平洋海温和同期西太平洋海温偏高时,西南地区夏季降水偏多。

Using the monthly observational precipitation data in 122 stations over southwest China (SWC), Hadley global sea surface temperature (SST) data and NCAR/NCEP monthly reanalysis data, the variation characteristic and summer precipitation of SWC and its possible causes are analyzed by the linear trend, empirical orthogonal function (EOF) and correlation analysis methods. The results show that the climate mean value of summer precipitation of SWC reaches to 535.1 mm, with positive trends during past 50 years. EOF analysis shows that the first mode of summer precipitation shows a south-north reverse distribution, and the second mode presents the southwest-northeast reverse distribution, and the third mode shows the northwest-southeast reverse distribution. The time series of EOF modes have significant interannual and interdecadal changes. Correlation analysis shows that precipitation in SWC is closely related to a variety of influencing factors such as near-surface high pressure, 200 hPa westerly jet, 500 hPa western Pacific subtropical high, northeast low vortex, and 850 hPa wind. In addition, the summer precipitation in SWC is also influenced by the SST in the middle and low latitudes of eastern Pacific. When the SST in early winter over the east and the west Pacific was than normal, the more summer precipitation in southwest China could be observed.