Diagnostic study on the torrential rains coupling with the lower southwest jets in Yunnan

Seven cases of the torrential rain coupled with the lower jets during Feb.1998-May,2002 in Yunnan are composite analyzed.The results show that the lower south-west jets is the main cause of torrential rain;Torrential rains usually occurred in the north of the lower jets where are characterized by cyclonic winds and lapse of wind speed;lower jets have an important effect on the transportation of the moisture and energy for the torrential rain.Some useful results by using the concept of moist potential vorticity are also obtained in this paper.