Numerical Simulation of a Typical Continuous Night Rain Processin the Western Sichuan Basin

Abstract

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”.

Keywords

• night rain
• “mountain-valley breeze”
• numerical simulation
• western sichuan basin