CAPE等环境参数在华北罕见秋季大暴雨中的应用

On Application of Environment Parameters:CAPE etc,to a Heavy Rain in Autumn in North China

采用中尺度数值模式MM5(V3)对2003年10月10～12日发生在华北地区的一次大暴雨过程进行模拟,利用模拟结果计算分析了对流有效位能(CAPE)、风暴相对螺旋度(SRH)、能量螺旋度指数(EHI),结果表明,以上3个参数对这次大暴雨的发生发展有较好的指示作用:在大暴雨发生前能量得到充分积累,大气处于强不稳定状态,强对流天气爆发后,不稳定能量逐渐释放减弱;大暴雨中心位于低层局地螺旋度大值中心南部等值线密集区。低层局地螺旋度大值中心轴线与切变线和地面倒槽辐合线走向一致,高层局地螺旋度与高空急流相对应;大暴雨过程主要发生在高风暴相对螺旋度结合低对流有效位能的环境中(SRH>200m2·s-2,CAPE<1500J·kg-1)。

The mesoscale numerical model MM5 （V3） is used to simulate the heavy rain process occurred in North China in Autumn. Based on the model products the environment parameters such as convective available potential energy （CAPE）, storm relative helicity（SRH） and energyhelicity index （EHI） are calculated and analyzed. The results show that the three parameters indicate the occurrence and development of the heavy rain. Much energy is accumulated before the heavy rain, and the rainstorm center lies in the isoline denseness which is in the south of the low-layer helicity center, at the same time, the severe storm take place under the condition of big-SRH and small-CAPE.