台风暴雨相当位涡诊断分析

THE DIAGNOSTIC STUDY OF HEAVY RAIN OF TYPHOON WITH THE EQUIVALENT POTENTIAL VORTICITY

位势涡度作为热力学与动力学相结合的物理量,能更有效地显示出暴雨系统的一些特点,国内外气象学者曾用位涡来分析诸如龙卷、冰雹等强对流天气,杨大升曾用位涡成功地研究过印度季风的爆发问题,并将位涡应用于我国的暴雨诊断分析上,但暴雨过程不可能是干绝热过程,将有大量的凝结潜热释放,而潜热释放对天气系统的发生发展起着重要的反馈作用,所以将位涡应用于暴雨诊断时还应考虑水汽凝结潜热的作用。为了弥补位涡的局限性。

A new physical variable, equivalent potential vorticity (EPV), which is used to diagnose the typhoon heavy rainfall, is derived according to the Ertel equation of generalized potential vorticity. Then, the budget equation of the EPV is derived, and each term of this equation is explained.When applying the EPV to the diagnostic analysis of a typhoon heavy rain process, it is found that the area of heavy rain occurred in the downstream of the negative center of EPV and near the maximum negative EPV tendency.Further analysis of the budget equation shows that the EPV can describe the thermodynamical and dynamical characteristic of heavy rain of typhoon. So the EPV is valuable for the prediction of typhoon heavy rain.