Effects Of Mid-high Latitude And Low Latitude Synoptic-scale Disturbances On Summer Precipitation In China And Numerical Simulations

Based on the daily precipitation of China station,and ERA-interim reanalysis data,this paper analyzed the spatio-temporal correlation between summer precipitation and synoptic scale disturbance intensity.Sensitivity experiments were designed using the Reg CM4.6(Regional climate model)to analyze the influence of the synoptic scale disturbance on summer precipitation by weakening the synoptic scale disturbance on different side boundary.The main conclusion are given as follows:(1)It is found that the precipitation in Northeast China is negatively correlated with the synoptic scale disturbance in the mid-high latitudes in reanalysis.In years of strong disturbance,the synoptic scale disturbance propagated southeast from Novaya Zemlya and converged over northeast China,weakening the westerly wind.Abnormal high pressure anticyclone was formed at 850 h Pa over Northeast China.The mid-high system was stronger,while the low latitude system was weaker.It was not conducive to the northward development of summer monsoon.There was high pressure divergence over Northeast China,which was not conducive to ascending movement.It was manifested as the decrease of precipitation over Northeast China.(2)In the experiment of removing the synoptic scale disturbance at mid-high latitudes,it was found that the southerly wind increased in intensity and range northward,and transported warm and wet air northward.The warm center appeared in the south side of Mongolia,the lower pressure decreased,the upper pressure increased,and the abnormal high pressure anticyclone was formed at the tropopause.Northeastern China and Tibet Plateau were located on both sides of the anticyclonic divergence,which is conducive to ascending motion.It is manifested by the increase of average precipitation.After removing the synoptic scale disturbance at low latitudes,only the local areas on the boundary are affected,and the changes in the other areas are not significant.(3)In 2020,the precipitation in Meiyu period is mainly due to synoptic scale disturbance.When the mid-high latitudes synoptic disturbance on the north or northwest boundary is weakened,the southward spread of E vector divergence on 850 h Pa is weakened,and zonal wind develops northward.The vorticity generated is conducive to the northward of subtropical high and Meiyu ends earlier in the Yangtze-Huaihe river basin.The conversion of atmospheric mean circulation kinetic energy to disturbance is northward.The westerly belt on the north side of the subtropical high moves northward and the precipitation center moves northward from the middle and lower reaches of the Yangtze River to the Huaihe River basin.When the synoptic scale disturbance in low latitudes is weakened,the southward wind in low latitudes weakened,and the precipitation in the Yangtze River basin increases slightly,but it had little influence on the evolution of rain belt.