【摘要】 利用中尺度模式MM5研究了2003年7月4～5日(简称“03.7”)的梅雨锋暴雨过程,该模式对这次暴雨过程有很好的模拟能力。应用假相当位温密集区定义锋面,梅雨锋锋生比暴雨早12h出现。此次暴雨过程中,急流发展比暴雨要早2h左右。低空急流的增强,负散度绝对值加大,促使低层强烈辐合,是本次暴雨的触发机制,而涡度的增强则是系统发展的结果。暴雨期间,对流层低层是平均湿位涡负值区,湿对称不稳定。然而,850hPa上湿位涡的弱正值区随暴雨中心(雨量>20mm·h-1)同步东移,说明其中心为湿对称弱中性。更多还原

【Abstract】 Mesoscale model MM5 is used in this paper to investigate the course of Meiyu front rainstorm in Nanjing on 4~5 July 2003(!03.7"), and it is shown thatits simulation ability is good about this process. The results show that the time of frontogenesis is earlier 12 h than that of heavy rain occurred. The results also suggest that the developmentof jet stream is about earlier 2 h than that of heavy rain. Increasing of the lower level jet stream and enhancing of absolute value of negative divergence that produce convergence on the low-level of troposphere to cause violently the occurrence of heavy rain. But it is the heavy rain that causes the increaseof the relative vorticity. The moist potential vorticity analysis during the heavy rain indicates that the lower level of troposphere is negative averagely in large area. This means the heavy rain have a feature of moist symmetric instability. But the result from the center of the heavy rain (rainfall > 20 mm·h+{-1}) isaccompanied by a small positive moist potential vorticity on 850 hPa. This shows that the center in heavy rain is almost moist symmetricstability after the release of convective energy.更多还原