东南沿海一次大暴雨过程的湿位涡分析

应用自动站和NCEP 1°×1°再分析资料，对2010年7月24日发生在东南沿海的一次大暴雨过程的湿位涡场进行了诊断分析.结果表明：鞍形场低层东南风低空急流输送的暖湿气流和对流层中低层来自东北方向的冷空气相互交汇是此次大暴雨发生的触发因子，大暴雨期间暴雨区上空对流层中低层等θse线较稀疏且陡立，大气对流稳定度较低，有利于湿斜压涡度发展，大暴雨发生在600 hPa上MPV、MPV1和MPV2正负过渡带附近，MPV1下负上正垂直叠加配置是暴雨发生发展的有利形势，湿位涡在900 hPa以下具有MPV1为负、MPV2为正的特征，当800 hPa以上MPV1正大值区变弱和900 hPa以下MPV2由正大值变为负大值时，大暴雨过程基本结束.

Analysis on the moist potential vorticity for a heavy rainstorm process in the southeast coastal areas of China

Based on the precipitation data from surface automatic stations and NCEP 1°×1° reanalysis data, moist potential vorticity (MPV) of a heavy rainstorm process occurred in the southeast coastal areas of China on July 24, 2010 was analyzed. The results indicate that the interaction between the warm moist air transport by the low level southeastly jet and the cold air from the northeast in the low troposphere in a saddle field is the trigger mechanism of this heavy rainstorm. During the heavy rainstorm, there are thin and stiff θse isolines above the rainfall area in the low troposphere, where the convective stability is so small that it is beneficial to the development of moist baroclinic vorticity. The heavy rainstorm area is located near the transition zone of positive and negative value of MPV, MPV1 and MPV2 at 600 hPa. The vertical overlapping of the positive and negative MPV1 areas at the lower and upper level is favorable to the appearance and development of rainstorm. MPV has the characteristics of MPV1＜0 and MPV2＞0 below 900 hPa. When the areas with positive and large value of MPV1 becomes weak above 800 hPa, as well as the positive and large value of MPV2 changes to the negative and large value below 900 hPa, the heavy rainstorm process basically ends up.