北疆暴雪过程的湿位涡诊断

Analysis of Moist Potential Vorticity to a Snowstorm Process in Northern Xinjiang

摘要:

利用NCEP1°×1°再分析资料，对2009年3月19～20日北疆沿天山一带一次暴雪天气过程进行诊断分析，着重探讨了湿位涡诊断在新疆暴雪预报中的应用。分析表明：暴雪的水汽输送有3个源地，低层负散度、向北倾斜的涡度“上负下正”分布、等 线的陡立密集带、垂直速度负值区与暴雪落区均有较好的对应关系。暴雪主要发生在MPV1＞0且正负值相互作用、MPV2绝对值迅速增加且等值线密集分布的区域。MPV1下传增大，大气对流不稳定能量释放，低层MPV2绝对值增大，大气湿斜压性增强，下滑倾斜涡度增长是暴雪形成的重要原因。

Abstract:

Using the NCEP 1°×1° reanalysis data, a snowstorm in northern Xinjiang from March 19 to 20 in 2009 was analyzed, and the application of wet potential vorticity was discussed specially. The results showed that there are 3 vapor source of snowstorm, and there are obvious relationship between negative divergence in lower layers, northward inclined vorticity distribution present a up negative and down positive appearance, equivalent potential temperature rise steeply intensive belt, rise velocity area and the falling area of snowstorm. This snowstorm occurred in a area of MPV1 positive and amplify distinctly, and absolute value mushroom and isoline intensive area of MPV2. MPV1 amplify down and atmosphere convective instability energy release. Absolute value of MPV2 at low level magnify and atmosphere wet baroclinicity enhance. It is a important reason that the development of down-sliding slantwise vorticity for the snowstorm formation.