运城一次罕见秋季长连阴雨分析及其对农业生产的影响

Analysis of a Rare Long Continuous Autumn Rain in Yuncheng and Its Impact on Agricultural Production

利用常规气象观测资料和NCEP再分析资料,分析运城市2019年9月的一次长达11 d的秋季长连阴雨过程。结果表明:运城市2019年9月这次连阴雨具有时间长、雨量大、范围广、局部地区伴有暴雨的特点。500 hPa冷空气扩散南下与副高外围暖湿气流交汇,是造成此次连阴雨的直接原因;700 hPa的西南急流与850 hPa的偏东气流在山西南部辐合为此次连阴雨过程提供了有利的水汽和动力条件;物理量诊断分析,连阴雨期间,垂直速度场上有持续的上升运动;700 hPa水汽通量场上在河套西南部有明显湿舌,将孟加拉湾水汽输送至运城;20日后副高南退到长江以北,运城高空转为西北气流,此次连阴雨过程结束。

Based on the conventional meteorological observation data and NCEP reanalysis data,an 11 day long continuous autumn rain process in Yuncheng City in September 2019 was analyzed.The results show that the continuous rain in September of 2019 in Yuncheng City has the characteristics of long time,heavy rainfall,wide range and heavy rain in some areas.The direct cause of the continuous rain is that 500 hPa cold air diffuses southward and converges with the warm and humid air flow around the subtropical high;The convergence of 700 hPa southwest jet and 850 hPa easterly flow in southern Shanxi provided favorable water vapor and dynamic conditions for the continuous rain process;According to the diagnostic analysis of physical quantity,there is a continuous upward movement in the vertical velocity field during the continuous rain;In the 700 hPa water vapor flux field,there is an obvious wet tongue in the southwest of Hetao,which transports water vapor from Bay of Bengal to Yuncheng;After 20 days,the subtropical high retreated south to the north of the Yangtze River,and Yuncheng turned to the northwest air stream at high altitude.The continuous rain process ended.