利用中尺度模式WRF研究了2017年7月15 -17日发生在四川盆地西部的一次典型连续性夜雨过程的形成机制， 重点讨论了“山谷风”局地环流对此次夜雨过程的作用。研究表明： （1）此次降水天气过程主要发生在500 hPa“北高南低”的环流形势背景下， 这种背景有利于北方冷空气向南输送； 850 hPa上台风东侧的偏南气流和副热带高压西侧偏南气流叠加形成输送带， 有利于低纬大量水汽和热量向四川盆地输送。（2）WRF模式模拟出的“山谷风”是此次夜雨过程的重要动力机制： 白天青藏高原东坡受“谷风”控制， 夜晚青藏高原东坡受“山风”控制， 从而产生了此次夜雨现象。（3）三种螺旋度都能够较好地解释夜间降水形成和“山谷风”之间的关系。

Used the mesoscale WRF model to study a continuous night rain processthat occurred in the western Sichuan Basin from 15 to 17 July 2017， and explored the formation mechanism of the night rain process， especially the local “valley wind” circulation.The main conclusions are as follows： （1）This weather process mainly occurs in the background of the 500 hPa “North High South Low” circulation， which is conductive to the southward transport of cold air.The southerly airflow on the east side of the typhoon at 850 hPa and the southerly airflow on the west side of the subtropical high are superimposed to from a conveyor belt， which is conducive to the transportation of large amounts of water vapor and heat to the Sichuan Basin at low latitudes.（2）The “valley wind” simulated by the WRF model is an important driving mechanism of the night rain process： during days， the eastern slope of the Qinghai-Xizang Plateau is controlled by the “valley wind” while the eastern slope of the Qinghai-Xizang Plateau is controlled by the “mountain wind” at night.（3）The three helicities can better explain the relationship of the night precipitation formation and the "valley wind”.