不稳定能量参数在一次强对流天气数值模拟中的应用

Application of Instability Energy Parameters to a Severe Convective Storm Forecast

摘要:

采用常规观测资料和1°×1°NCEP/NCAP再分析资料,运用MM5V3.7高分辨率中尺度数值模式,对2004年7月12日17时30分前后发生在江苏南通的一次强中尺度对流系统(龙卷)进行模拟分析。结果表明:南通上空处在上干冷、下暖湿的大气不稳定层结中。干冷空气侵入与边界层暖湿气流强烈辐合,大量能量释放造成了本次龙卷的发生。运用数值模拟结果,计算了最佳对流有效位能I_BCAPE、对流抑制能量I_CIN、归一化对流有效位能I_NCAPE、能量—螺旋度指数I_EHI和强对流天气威胁指数I_SWEAT等不稳定能量参数。通过分析上述参数的空间分布和在南通上空的时间分布,发现它们对强对流天气的发生有一定反映。

Abstract:

The atmospheric unstable energy accumulation and release play a key role in the formation of severe convective weather.A mesoscale severe convective storm with tornado and hails at 1730 BST July 12,2004 in Nantong,Jiangsu Province is analyzed in this paper by using the conventional observational data and the NCEP/NCAR 1°×1° reanalysis data.The results show that beore 1730 BST July 12 the stratification was unstable with dry and cold air at the upper level and warm and moist air at the lower level over Nantong,and dry air intrusion and its strong convergence with the warm and moist air in the boundary layer induced the release of unstable energy and the formation of tornado.Based on the numerical simulation results,parameters I_BCAPE,ICIN,INCAPE,IEHI and ISWEAT etc are calculated,and it is found that the parameters and indexes were good indicators for the severe weather including this tornado.