Abstract:

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.

Key words: Precipitation anomaly, Circulation anomaly, SST effect