【作者】 王子谦； 朱伟军； 段安民；

【Author】 Wang Ziqian1,2 , Zhu Weijun1 , Duan Anmin2 (1.Atmosphere Sciences College,Nanjing University of Information Science & Technology, Jiangsu Nanjing 210044; 2.LASG,Institute of Atmospheric Physics,Chinese Academy of Science, Beijing 100029)

【机构】 南京信息工程大学大气科学学院； 中国科学院大气物理研究所LASG；

【摘要】 基于湿位涡(MPV)诊断分析和倾斜涡度发展(SVD)理论,本文对2007年11月一次孟加拉湾热带风暴北上造成青藏高原暴雪的天气进行了研究。结果表明:热带风暴螺旋云系移动至高原东南部受陡峭地形抬升与高层北侧下滑的干冷空气(MPV1正值带)的交汇是导致这次天气过程的重要原因。由于等熵面密集且明显倾斜,在降雪区上空附近大气弱稳定区,负的MPV2对总湿位涡MPV的贡献超过了MPV1,SVD得到较大增长,同时使得MPV<0,导致条件性对称不稳定的产生,有利于倾斜涡度的发展。条件性对称不稳定机制是本次暴雪发生发展的一种可能的重要触发机制。更多还原

【Abstract】 Based on the diagnosis of moist potential vorticity (MPV) and the theory of slantwise vorticity development (SVD), a case study of snowstorm in the Tibetan plateau induced mainly by a Bay of Bengal storm in November 2007 was carried out. The results show that the interaction of the storm’s spiral cloud band and the down-sliding dry cold air (positive MPV1 band) over the steep southern fringe of the plateau is the main reason for this synoptic process. Owing to the dense and obvious slantwise isentropic surface, the contribution of negative MPV2 to moist potential vorticity (MPV) is more than MPV1 over the snowfall area where atmosphere is weak stable. It further leads to the sharp growth of SVD. Moreover, negative MPV makes a favorable background of the generation of conditional symmetrical instability. The conditional symmetrical instability is beneficial to the development of slantwise vorticity, and it is a possible important trigger mechanism to this snowstorm.更多还原