中文摘要：

利用NCEP／NCAR再分析资料和实测资料对2004年6月24-25日的一次江苏暴雨过程进行了分析，并且根据湿位涡守恒原理和倾斜涡度发展理论，对这次暴雨过程中的湿位涡进行了诊断分析，结果表明：此次暴雨由中尺度低涡、切变线直接触发产生；西南低空急流的稳定维持为这次暴雨的发生提供了重要的水汽条件；当负湿位涡向上的扰动高度增加、强度增强，高低空正负湿位涡区配合较好时常会出现强降水。另外，利用EVAD技术由多普勒雷达基数据定量计算了这次过程的平均散度场，通过分析其演变情况，发现：低层散度场由辐散逐渐向辐合过渡、高层散度场由辐合逐渐向辐散过渡时，预示着强降水将要发生，如果出现相反的变化趋势，则降水减弱或停止；低层由辐散向辐合、高层由辐合向辐散的转折出现时间早于强降水出现的时间，对强降水产生有预示作用，对预报员准确作出短时临近预报预警具有重要实际应用价值。

英文摘要：

By using the NCEP/NCAR reanalyzed data and observation data a heavy rainfall occurred in Jiangsu during 24--25 June 2004 has been analyzed. The results show that the process is resulted directly from mesoscale vortex and shear line. It is found that the lower south-west jets have an important effect on the transportation of the moisture and energy. The moist potential vorticity in the heavy rainfall has been diagnostically studied in terms of moist potential vorticity principle and slantwise vorticity development theory. It is shown that heavy rainfall will occur when negative moist potential vorticity disturbance upward become stronger and the positive and negative moist potential vorticity cooperated well. Furthermore, radar base data was used to calculate quantitively the atmospheric average divergence by applying the EVAD techniques and its evolution is investigated. The divergence gives an indication of rainfall before it. That is to say, when the divergence field at the lower level changes from divergence to convergence and the divergence field at the higher level changes from convergence to divergence, gradually the rainfall will strengthen, but if there is opposite situation the rainfall will become weaker or will stop. The transition is earlier than the heavy rainfall.