梅雨锋暴雨中β尺度系统的结构

ON STRUCTURE OF MESO-β-SCALE SYSTEMS IN THE MEI-YU FRONT

本文利用中尺度数值模式MM5，选取1981年6月27日梅雨锋暴雨个例进行数值模拟，分析了梅雨锋上的中β尺度雨团和中β尺度系统的空间结构特征。结果指出，与中β尺度雨团相对应的地面气压场上是中尺度低压槽或闭合的中低压系统；在雨团发生初期，其垂直结构为暖心涡柱对流斜压扰动；而在雨团发展期，发展为暖心涡柱强对流混合型低涡；在雨团衰弱期，为暖心涡柱非对流前倾填塞涡。同时还揭示了在北雨团发展南雨团减弱期，在低空流场上对应着呈气旋性打转的一双中β尺度涡旋，即中β尺度的涡对。

The heavy rainfall event of June 27, 1981 in the Mei-Yu front as a case is slmulated byusing the mesoscale model MM5. This paper analyses meso-β-scale rain cluster (i. e. rainfall center for larger than 10mm/hr) and characteristics on space structure of meso-β-scalesystems in the Mei-Yu front. It shows that a system connected to meso-β-scale rain cluster is a mesoscale trough or a mesoscale low pressure on the surface. Its vertical structure is awarm-cored vorticity column with convectional baraclinic disturbance at the genesis stage ofrain cluster,or with a severe convective hybrid vortex at the development stage, or with afilling vortex of nonconvective backward tilting at the weaking stage. Moreover, a pair ofmeso-β-scale vortexes,or a vortex pair,in cyclonic rotation at the low-level stream fieldis discovered during development of the northern rain cluster and weaking of the southernone.