2013年冬季长江中下游地区一次高架雷暴过程的成因分析  

Analysis on the formation mechanism of an elevated thunderstorm over the middle and lower Yangtze Basin in February 2013

作　　者：黄小刚[1] 费建芳[1] 孙吉明[2] 程小平[1] 

机构地区：[1]解放军理工大学气象海洋学院,南京211101 [2]空军航空大学航空理论系,长春130022

出　　处：《气象学报》2017年第3期429-441,共13页Acta Meteorologica Sinica

基　　金：国家自然科学基金重点项目(41230421);国家重点基础研究发展计划973项目(2013CB430101)

摘　　要：综合应用常规观测资料、再分析资料、多普勒雷达探测资料等多源数据,分析了2013年2月发生在长江中下游地区一次高架雷暴过程的形成机制。结果表明,此类高架雷暴过程发生在冷锋后部对流稳定的环境大气中,其主要形成过程为:首先气块在地形强迫和锋面抬升作用下产生垂直运动,由于对流稳定环境大气的抑制,气块只能到达较低的中性浮力高度并产生与环境大气之间的绝对地转动量差(ΔM),在ΔM调整机制作用下自低层抬升的气块将产生沿等熵面的惯性加速度从而加强了倾斜运动,当暖湿气流沿锋面爬升至约700 hPa高度时,在辐合切变线和高、低空急流耦合等的共同作用下,倾斜运动进一步加强,并在此过程中产生对称不稳定并通过反馈机制促进倾斜运动的进一步发展。在地形强迫和锋面抬升的基础上,ΔM调整与对称不稳定的共同作用使得冷锋后部锋区上空产生旺盛的倾斜运动,倾斜运动的持续发展使对流得到组织化,产生带状的对流云和降水带,最终形成了雷暴等强对流天气。总之,在对流稳定的环境大气条件下,由于地形强迫和锋面抬升、ΔM调整、辐合切变线和高低空急流耦合以及对称不稳定等机制的联合作用激发了倾斜对流运动的强烈发展,使倾斜对流有效位能大量累积并释放,最终形成了此次冬季高架雷暴天气过程。An elevated thunderstorm process occurring in the middle and lower reaches of the Yangtze River region in February 2013 was investigated using conventional observation data, reanalysis data and Doppler radar data. The results show that this elevated thunderstorm formed and remained in the upper air behind the surface cold front. Its evolution process is described as follows. The air parcel in the vicinity of the cold front was lifted by the topographic and frontal forcing first. However, the air parcel could only reach the lower height of neutral buoyancy due to the convective inhibition in a stable atmospheric environ- ment. As the parcel ascended, its potential temperature and geostrophic absolute momentum were conserved, thereby leading to an absolute momentum anomaly （AM） between the parcel and the atmosphere at the level of neutral buoyancy in the ba roclinic atmosphere. The parcel then experienced an inertial acceleration and the inertial adjustment occurred along the neutral buoyancy surface, which forced the parcel to move along a slantwise path and the AM adjustment circulations formed. Once the warm moist air reached 700 hPa level, the slantwise motion further strengthened by the shear line and the coupling of the two jets at the upper and lower levels. Accompanied with the AM-adjustment, the conditional symmetric instability （CSI） genera- ted. The AM-adjustment and CSI circulations both promoted the development of slantwise convection above the cold front. In a word, the interwoven effects of the topographic and frontal forcing, the atmospheric stability, AM-adjustment, the shear line and the coupling of the upper and lower level jets, and CSI greatly promoted the development of slantwise convection, which released the slantwise convective available potential energy and caused this elevated thunderstorm process.

关 键 词：高架雷暴 ΔM调整 对称不稳定 地形强迫 锋面抬升 

分 类 号：P446[天文地球—大气科学及气象学]