Large-scale Circulation Characteristics Of Precipitation Anomalies In Southern China In The Autumn Of 2016 And Their Relationship With SST

In the autumn of 2016,the southern China suffered from the most heavy rainfall in the past 50 years.Based on the precipitation data from weather stations in China,UK Hadley Centre SST(Sea Surface Temperature)and NCEP/NCAR reanalysis datasets,this paper studies the large-scale atmospheric circulation characteristics of the abnormally heavy precipitation events over the southern China in the fall of 2016 and its relationship with SST.The main conclusions are as follows:(1)Results show that the subtropical westerly jet in East Asia was much stronger in the fall of 2016,and the southern China was just located to the right of the jet stream entrance,which was conducive to an ascending motion.The western Pacific subtropical high also was much stronger than its normal,with a larger area and more northwestward shifted location.The anomalous southeasterly winds on the southwest side of the western Pacific subtropical high transported warm and moist air from the tropical Pacific to the southern China,leading to heavy precipitation there.(2)More landfalling typhoons along the coast of the Southeast China also contributed to the abnormally heavy precipitation over the southern China in the fall of 2016.(3)Further analysis shows that the heavy rainfall event was both related to the abnormally higher SST over the equatorial western and southeastern Pacific simultaneously on inter-annual time scales,and anomalous warming over the North Atlantic on inter-decadal time scales.A series of numerical model simulations using CAM5.3(Community Atmosphere Model Version 5.3)manifests that the abnormally higher SST over the equatorial western Pacific,on one hand,can lead to the western Pacific subtropical high become much stronger,with northwestward shifted location,by triggering a wave train similar to the Summer East Asia-Pacific Pattern Teleconnection.On the other hand,through Gill-type atmospheric response in the lower troposphere,the anomalous cyclonic circulation(similar to the South China Sea-western Pacific monsoon trough in summer),which has an impact on the autumn precipitation in the southern China,can be generated from the South China Sea to the east of the Philippines.When the SST of the southeastern Pacific is abnormally high,the atmospheric circulation anomalies over the tropical western Indian Ocean,South China Sea and tropical western Pacific are caused by a downstream-propagating teleconnection wave train,thus affecting the autumn precipitation over the southern China.As for the inter-decadal warming of the North Atlantic,the Kelvin wave,which is transmitted eastward in the tropical region,can be excited,which may have an impact on the subtropical circulation in the northwestern Pacific,and then on the autumn precipitation in the southern China.