基于湿位涡(MPV)诊断分析和倾斜涡度发展(SVD)理论,研究了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事件。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)相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这次暴雪发生、发展的一种可能的重要机制。 Based on the MPV diagnostic analysis and the SVD theory, a weather event triggered by a tropical storm over the Bay of Bengal north of the Qinghai-Tibet Plateau in November 2007 was studied. The results show that the tropical cyclone cloud system moved to the southeastern part of the plateau where the steep terrain uplifted and the dry cold air (MPV1 positive band) falling on the north side of the upper layer intersected. This was the main reason for this weather process. As the isentropic surface is dense and obviously tilted, the negative MPV2 contributes more to MPV than the MPV1 in the weak atmospheric stable region near the snowfall area, and the MPV1 increases greatly and the MPV <0 leads to the conditional symmetry Instability is conducive to the development of tilt vorticity. The conditional symmetrical instability mechanism is a possible and important mechanism for the occurrence and development of Blizzard.