2019年12月吉林省降水异常偏多成因分析

本文从大尺度大气环流和海温异常方面对2019年12月吉林省降水异常成因进行分析，并探究前期秋季日本附近关键区海温异常对吉林省12月降水异常的可能影响。结果表明：1981—2019年吉林省12月降水有明显增多的趋势，在降水年代际偏多的气候背景下，2019年12月吉林全省降水量为常年同期的227.5%，居1981年以来同期多雨雪第4位。前期秋季日本附近关键区海温异常偏暖是12月吉林省降水异常偏多的驱动条件之一，在前期海温异常偏暖年：鄂霍茨克海至日本上空为异常反气旋，阻塞高压活跃，贝加尔湖附近地区为负高度距平，东亚冬季风系统减弱，局地海温的异常升高使其上空的水汽含量增加，配合东亚冬季风异常为吉林省上空带来了充足的水汽；另一方面，由于中纬度45°N附近为西风距平，为东北地区带来冷空气，在槽前正涡度平流作用下，有上升运动，为降水提供了动力条件。在前期海温异常偏冷年：中国东北地区盛行西风，东亚冬季风偏强，中国东部沿海有北风异常，西伯利亚高压偏强，吉林省降水的水汽和动力条件不足，降水异常偏少。

Cause analysis of enhanced precipitation anomaly in December of 2019 in Jilin province

The characteristics of precipitation anomalies in December of 2019 in Jilin province were analyzed based on atmospheric circulation and sea surface temperature (SST) anomaly.The possible influence mechanism of SST anomaly in key areas near Japan in the early autumn on this precipitation anomaly was studied.The results show that since 1981, the precipitation in December in Jilin province has increased significantly.Under the climate background of more inter-decadal precipitation, the precipitation in December of 2019 in Jilin province is 227.5% of that in the same period of the history year, ranking the fourth place with more rain and snow in the same period since 1981.The anomalous warm SST in key areas near Japan in the early autumn is one of the driving conditions for the anomalous heavy precipitation in Jilin province in December.In the anomalous warm SST years in the early autumn, on the one hand, there is an abnormal anticyclone from the Sea of Okhotsk to Japan, and the blocking high is active.There is a negative height anomaly over the area around Lake Baikal, and the East Asian winter monsoon system is weakened.The abnormal increase of local SST increases the water vapor content in the East Asian winter monsoon season, which brings sufficient water vapor over Jilin province.On the other hand, due to the west wind anomaly near the mid-latitude 45°N, cold air is brought to Northeast China.Under the action of positive vorticity advection in front of the trough, there is upward movement, which provides dynamic conditions for precipitation.In the early SST abnormally cold years, there are zonal circulation in middle and high latitudes, prevailing westerly winds in Northeast China, strong winter winds in East Asia, abnormal northerly winds in East China, and strong Siberian high.Insufficient water vapor and dynamic conditions of precipitation in Jilin province result in less precipitation anomaly.