我国南方西南和中东部区域两次持续性低温雨雪过程与关键环流系统的关系研究OACSTPCD

By using the NCEP reanalysis data and the daily temperature and precipitation data of 753 stations provided by the China National Meteorological Information Center,two low temperature rain and snow processes lasting more than 10 days of southwestern and central-eastern of southern China were compared.Results show that:(1)both processes deepen the East Asian trough in the middle and high latitudes of Eurasia,but there are differences in the circulation situation.The southwestern process was"north high south low"situation,and the key ridge area centered in Lake Baikal,while the central-eastern process was"north high-south low"and"west low-east high"coexisted,the key ridge area extends from the Ural Mountains to Lake Baikal.The anomalous circulation of the two processes was related to the eastward propagating wave train of the North Atlantic Ocean.(2)The Ural Ridge began to develop three days before the southwestern process took place,and then moved east to Lake Baikal,forming a stable situation,while the Ural Mountain-Baikal ridge region of the central-eastern process began to develop one week before the process and reached its strongest on the start date.Both processes are accompanied by Mongolian high pressure moving southeast to make the ground cooling.The ridge area at 500 hPa ahead of the Mongolian high pressure two days change.The cooling of the southwestern process was mainly influenced by cold advection and adiabatic cooling,while the central-eastern process was influenced by cold advection.(3)The water vapor of southwestern process came from the Bay of Bengal area,influenced by the southern branch trough.Differently,the water vapor of central-eastern process came from the Bay of Bengal,the South China Sea and the western Pacific,influenced by the southern branch trough and the West Pacific subtropical high.The positive balance of water vapor in the two processes mainly comes from the southern boundary.The above research results can provide references for forecasting the persistent low temperature rain and snow process in southwestern and central-eastern of southern China.