西南地区夏季降水变化与太平洋海温的关系

The Relationship between Summer Precipitation Variation in Southwest China and Pacific Ocean SST

为研究西南地区夏季降水变化与太平洋海温的关系,利用中国气象局提供的西南地区76站1961~2022年共62年逐日气象降水观测数据与哈德莱中心网格距为1˚ × 1˚的海温资料、美国国家环境预报中心(NCEP)和国家大气研究中心(NCAR)的网格距为2.5˚ × 2.5˚再分析资料,通过相关分析、合成分析、经验正交函数分解(EOF)、奇异值分解(SVD)等方法,对西南地区夏季降水与太平洋海温的关系进行了详细研究。得到以下结论:(1) 西南地区近60年的夏季降水量呈下降的趋势,降水的空间分布不均,自南向北减少。同时,降水与海温的相关系数表明,西南地区6~8月降水与赤道西太平洋海温关键区(125˚E~175˚W, 15˚S~20˚N)呈显著的正相关,即关键区海温异常偏暖(冷),西南地区夏季降水偏多(少)。(2) EOF及合成分析表明,关键区海温异常偏高时,西南地区的降水偏多且主要集中于四川东部、重庆及贵州地区;而在海温异常偏低的年份时,降水明显偏少。(3) SVD分析表明,关键区前期冬季、春季及当期夏季海温与西南地区夏季降水量均存在显著的正相关关系,即关键区海温异常偏暖(冷),西南地区夏季降水偏多(少),与相关系数分析及合成分析的结果一致。

To investigate the relationship between summer precipitation variations in the Southwest re-gion of China and Pacific sea surface temperatures (SST), this study utilizes daily meteorological precipitation observations from 76 stations in the Southwest China provided by the China Mete-orological Administration for a period of 62 years (1961~2022), along with Hadley Center SST data with a grid resolution of 1˚ × 1˚ and reanalysis data from the National Centers for Environ-mental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) with a grid resolution of 2.5˚ × 2.5˚. Through methods such as correlation analysis, composite analysis, em-pirical orthogonal function (EOF) analysis, and singular value decomposition (SVD), the relationship between summer precipitation in the Southwest region of China and Pacific SSTs is analyzed in detail. The following conclusions are drawn: (1) Summer precipitation in the Southwest China has exhibited a decreasing trend over the past 60 years, with uneven spatial distribu-tion and a decrease from south to north. The correlation coefficients between precipitation and SST indicate a significant positive correlation between summer precipitation in the Southwest region during June to August and the SST of key region in the western equatorial Pacific (125˚E~175˚W, 15˚S~20˚N). Specifically, when the SST anomaly in the key region is warm (cold), there is an excess (deficit) of summer precipitation in the Southwest China. (2) EOF and compo-site analysis indicate that during years with higher SST anomalies in the key region, there is ex-cessive precipitation in the Southwest China, primarily concentrated in the eastern part of Sichuan, Chongqing, and Guizhou. Conversely, during years with lower SST anomalies, the precipitation is obviously less. (3) SVD analysis demonstrates a significant positive correlation between SST anomalies in the key region during the preceding winter, spring, and concurrent summer, and summer precipitation in the Southwest China. This finding is consistent with the results of correlation coefficient analysis and composite analysis, indicating that when the SST anomaly in the key region is warm (cold), there is an excess (deficit) of summer precipitation in the Southwest region of China.