西南暖湿气流

伴随西南暖湿气流，华北回流降水的水汽来自南方。

The moisture came from the South along with the south-west air flow .

这次降雨是受西南暖湿气流和冷空气的共同影响，降水、降温都比较明显。

This rainfall is influenced by the southwest warm and humid air and cold air jointly as well as the rainfall and temperature decline will both be obvious .

南下冷空气在江南一带被来自低纬的西南暖湿气流和东南暖湿气流所切断，形成一高位涡冷空气中心。

The air was cut by the Southwest and Southeast warm moist air flow from low latitude in the vicinity of South of the Yangtze River , and formed a high PV center of cold air .

模拟结果分析表明：此次积层混合云的水汽辐合主要是由西南暖湿气流提供，且西南暖湿气流区域的大气层结始终处于对流不稳定状态，而均匀上升气流场中的波动导致了对流云镶嵌其中。

The simulation results shows that , moisture convergence is mainly caused by warm-moist airflow from southwest , and the atmospheric stratification of warm-moist airflow area keeps in an unsteady state all the time , while the dramatic fluctuations of updraft lead to embedded convective clouds .