西南雨季降水异常水汽输送变化特征

Characteristics of Water Vapor Transport Changes in Abnormal Rainfall during the Southwest Rainy Season

摘要: 为了研究西南地区存在的异常水汽输送的变化特征，利用西南地区81个气象台站点1960~2022年共63年的逐日气象降水量观测资料和同期ERA5逐月再分析资料，数据的网格分辨率0.25˚ × 0.25˚，通过天气学诊断分析、径向基函数插值算法、t检验法和显著性检验等方法，对西南地区的雨季异常水汽输送特征进行了详细研究，其研究结论表明：1) 西南地区雨季降水量自1960年起呈现显著下降趋势，具有约11年的周期性变化周期内分布并不均匀，多为上升慢，跌落快。当前正处于新周期的起始阶段，预计将经历一个缓慢的上升期。2) 每30划分一个年际为统计口径，越靠近当下的年际的雨季降水量越低，水汽输送也越弱，代表水汽输送的水汽通量散度和垂直积分都会越低，垂直积分的下降趋势略弱于散度。3) 西南地区还存在一个异常区域位于103˚E~106˚E区域，该区域内站点之间存在水汽输送的共通性，水汽输送和异常降水都与整体相反，拥有相对独立水汽输送通道，根据四轮30年际统计发现异常带将逐渐扩大，空间上沿向外扩散，伴随整体周期性的上升，除异常带外的其他地区将经历水汽输送和雨季降水的增长，而异常带地区将呈现与整体趋势相反的异常低值。

Abstract: To investigate the characteristics of anomalous water vapor transport in Southwest China, we utilized daily precipitation observations from 81 meteorological stations in Southwest China spanning 63 years (1960~2022) and monthly ERA5 reanalysis data with a grid resolution of 0.25˚ × 0.25˚. Through synoptic diagnostic analysis, radial basis function interpolation, t-test, and significance testing, we conducted a detailed study on the characteristics of anomalous moisture transport during the rainy season in Southwest China. The study concluded that: 1) Since 1960, the rainy season precipitation in Southwest China has shown a significant downward trend, characterized by an approximately 11-year periodic cycle. Within this cycle, the distribution is uneven, with a slow rise and a rapid fall. Currently, it is at the beginning of a new cycle, expected to experience a slow upward trend. 2) When dividing into 30-year intervals for statistical purposes, the closer to the present, the lower the rainy season precipitation and the weaker the moisture transport. This is reflected in lower moisture flux divergence and vertically integrated moisture transport, with the decline in vertical integration being slightly less pronounced than that in divergence. 3) An anomalous region exists between 103˚E and 106˚E, where the meteorological stations exhibit commonality in moisture transport. Both moisture transport and anomalous precipitation in this region are contrary to the overall trend, indicating a relatively independent moisture transport channel. Statistical analysis over four 30-year intervals reveals that this anomalous belt is gradually expanding spatially, with the anomaly spreading outward. As the overall periodic rise continues, regions outside the anomalous belt will experience growth in moisture transport and rainy season precipitation, while the anomalous belt will exhibit anomalously low values opposite to the general trend.