关键词: 暴雨, 数值模拟, 诊断分析, 对流有效位能, 边界层幅合线, MCC

Abstract: A mesoscale convective system (MCS) which happened around Shangdong Province in the middle spring 2003 induced heavy rainfall. In the unstable large scale atmosphere, trigger conditions determine when and where the convections come into being. However, these conditions lie in boundary level above ground with small scales, and the general surface and rawinsonde data can not reveal them. A method of numerical simulation and sensitivity simulation together with objective analysis are conducted, and its trigger mechanism can be diagnosed. The results of diagnosis indicate that two developments of MCS bring up this heavy rain. The first can be called a typical Huabei MCS, whose initial convections are arisen by terrain forced climb; the second initial convections are arisen by boundary convergence lines in the afternoon, meantime the lower level cold air from Huabei Plain also contributes to their formation. So the maximum convective available potential energy (MCAPE) is able to give right information on where the initial convections will occur.

Key words: heavy rainfall, numerical simulation, diagnostic analysis, convective available potential energy, boundary convergence line, MCC