西南地区夏季降水变化与南亚高压的关系
The Relationship between Summer Precipitation Changes in Southwest China and the South Asian High

为进一步研究西南地区夏季降水变化与南亚高压的关系，利用1961~2022年6~8月西南地区76个气象观测站的逐日气象观测降水量资料、同期NCEP/NCAR的月平均再分析资料(包括高度场、风场、地面气压场、相对湿度场、比湿场)，网格距2.5？ × 2.5？，通过合成分析、EOF分解、SVD奇异值分解、南亚高压特征量等方法，详细探讨了西南地区夏季降水变化特征与南亚高压的关系其主要结论如下：(1) 西南地区1961~2022年夏季降水呈负趋势，每10年夏季平均降水量减少4.377 mm，降水量空间分布不均匀，大致为自西北向东南呈增加趋势。(2) 根据EOF分析，前三个模态累计方差贡献率达到了51.6%，能够较好地反映出夏季降水的空间分布类型。第一模态表明西南地区整个地区全年都呈现出多雨(少雨)的趋势。第二模态呈现出正距平区和负距平区交错分布的情况。第三模态呈现出夏季降水从北向南呈“正–负–正”分布类型的情况。(3) 1961~2022年南亚高压特征量不仅存在明显的年际变化，而且也存在明显的年代际变化，除脊线位置外。从1961~2022年，南亚高压的强度在逐渐增强，面积在逐渐增大，东脊点位置逐渐偏西，西脊点位置逐渐偏东，脊线位置逐渐偏南。(4) 从1961~2022年夏季南亚高压各特征参数与西南地区同期降水的点相关分布中可以看出，南亚高压脊线位置、面积指数、强度指数与西南地区同期降水关系最密切。从西南地区夏季降水与同期南亚高压的SVD分解表明：第一模态空间分布型反映了南亚高压偏弱(强)年与西南地区偏旱(涝)年对应关系一般。第二模态空间分布型反映了南亚高压偏弱(强)年与西南地区偏旱(涝)年对应关系较好。
In order to further study the relationship between summer precipitation change in Southwest China and South Asia high, the daily meteorological observation precipitation data of 76 mete-orological stations in Southwest China from June to August from 1961 to 2022 and the monthly average reanalysis data of NCEP/NCAR in the same period (including height field, wind field, surface pressure field, relative humidity field and specific humidity field) were used. By means of composite analysis, EOF decomposition, SVD singular value decomposition, South Asia high characteristic quantity and other methods, the relationship between summer precipitation vari-ation characteristics and South Asia high in Southwest China is discussed in detail. The main conclusions are as follows: (1) The summer precipitation in Southwest China showed a negative trend from 1961 to 2022, and the average summer precipitation decreased by 4.377 mm every 10 years. (2) According to the EOF analysis, the cumulative variance contribution rate of the first three modes reached 51.6%, which can better reflect the spatial distribution type of summer precipitation. The first mode shows that the whole southwest region shows a trend of more rain (less rain) throughout the year. The second mode shows the staggered distribution of positive anomaly area and negative anomaly area. The third mode shows a “positive-negative-positive” distribution pattern of summer precipitation from north to south. (3) From 1961 to 2022, the characteristics of the South Asia High not only have obvious interannual changes, but also have obvious interdecadal changes, except for the ridge position. From 1961 to 2022, the intensity of the South Asian High is gradually increasing, the area is gradually increasing, the eastern ridge point is gradually westward, the western ridge point is gradually eastward, and the ridge line