川渝地区夏季降水异常水汽输送差异

利用川渝地区1960—2006年34站逐月降水量资料和美国NCEP/NCAR同期逐月风场、比湿场和地面气压场资料,网格距2.5°×2.5°,采用EOF分解、区域降水指数、合成分析等方法,详细讨论了川渝地区夏季降水量多、少雨年水汽通量的纬向、经向、整层输送及水汽通量散度的差异。川渝地区夏季降水量标准化距平EOF分解结果表明把川渝地区夏季降水量作为一个整体来分析是合理的。区域降水量指数能很好地揭示出川渝地区夏季降水量的多寡。合成分析表明川渝地区夏季降水量多、少雨年水汽输送通量的纬向、经向、整层输送及水汽通量散度存在着明显差异,多雨年孟加拉湾、南海、西太平洋的水汽输送通量显著增强,水汽输送通量辐合比少雨年显著增强,为川渝地区夏季降水提供了丰沛的水汽条件,有利于川渝地区夏季降水量的异常偏多;少雨年则反之。

Characteristics of Water Vapor Transport of Summer Precipitation Anomalies in Sichuan-Chongqing Region

Based on the precipitation at 34 stations in the Sichuan-Chongqing region and the mean daily reanalysis geopotential height, wind field, humidity field and surface pressure field data (grid 2.5°×2.5°) from 1960 to 2006, the different characteristics of zonal, meridional and the whole layer water vapor transfer in the Sichuan-Chongqing region are studied in terms of the empirical orthogonal function, regional precipitation index, composite analysis, and so on. The result of EOF for the summer standardized anomaly precipitation shows that it is reasonable for summer precipitation as a whole in the Sichuan-Chongqing region. The method of regional precipitation index is showed that there is significant difference in the summer precipitation in the Sichuan-Chongqing region. The method of composite analysis indicates that there are marked differences for the water vapor flux of zonal wind, meridional wind as the whole and the water vapor flux divergence between the good and poor years. The results showed that the water vapor flux of zonal wind, meridional wind as the whole and the water vapor flux divergence are intensified in good years, which supplied the ample conditions of the water vapor transport and it is advantageous of increasing of the precipitation in the Sichuan-Chongqing region, and vice versa in poor precipitation years.