2020年6月贵州连续性暴雨成因分析

2020年6月贵州出现4次具有明显夜雨特征的连续性暴雨天气过程,以短时强降水为主,强度大,局地性较强。该文利用NCEP/NCAR再分析资料,详细分析高空形势、东亚西风急流、低空水汽条件和动力条件以及海温特征,并采用西伯利亚高压强度指数分析冷空气强度,结合贵州区域自动站降水观测资料,分析暴雨成因,结果表明:2020年6月欧亚大陆上空呈现正-负-正的波型分布,有利于高纬地区高空槽引导冷空气南下;副热带高压位置较常年同期偏北偏西且稳定维持,有利于水汽输送到贵州;东亚西风急流强度较强,其西段位置较常年同期略偏南,贵州位于急流轴右侧且处于水汽辐合区、垂直速度负值区,动力条件和水汽条件的有效配合,有利于贵州暴雨天气发生;贵州暴雨对西伯利亚高压强度指数具有较好的响应,但暴雨发生时间比西伯利亚高压强度指数滞后1 d;赤道西太平洋地区海温表现为偏暖,赤道东太平洋地区海温表现为偏冷,且印度洋呈现出西正东负的偶极子型海温异常,此类海温配置,有利于激发印度洋和西太平洋的反气旋环流,为水汽输送到贵州上空创造了有利条件。

Analysis on the Causes of Continuous Rainstorm in Guizhou in June 2020

In June 2020, Guizhou experienced 4 consecutive torrential rain processes, with obvious characteristics of night rain, which are mainly short-term heavy rainfall, with high intensity and strong locality. In this paper, NCEP/NCAR reanalysis data are used to analyze the upper-altitude situation, East Asian westerly jet, low-altitude water vapor conditions and dynamic conditions, and SST characteristics in more detail;the analysis of the cold air intensity by using the Siberian high intensity index are combined with the precipitation observation data from the automatic station in Guizhou to analyze the causes of the torrential rain in Guizhou in June 2020, the results show that the positive-negative-positive wave pattern over the Eurasian continent in June 2020 was conducive to the high-altitude troughs in high latitudes to guide cold air southward;the location of the subtropical high was more north and west than that of the same period of the normal years, and it was stable, which was conducive to the water vapor transport to Guizhou;the intensity of the westerly jet over East Asia is strong, and the position of its western segment is slightly southward compared with the same period of the normal years, in addition, Guizhou is located on the right side of the jet axis, in the water vapor convergence zone and the negative vertical velocity zone, so the effective coordination of dynamic conditions and water vapor conditions is conducive to the occurrence of heavy rain in Guizhou;the heavy rain in Guizhou responded well to the Siberian high intensity index, but the occurrence time of heavy rain is 1 d later than the index;the SST in the western equatorial Pacific Ocean is warmer, the SST in the eastern equatorial Pacific is colder, and the Indian Ocean presents a dipole-type SST anomaly of positive west and negative east. This kind of SST configuration is conducive to stimulating the anticyclonic circulation in the Indian Ocean and the western Pacific, creating favorable conditions for the transportation of water vapor over Guizhou.