“威马逊”引发广西暴雨的等熵位涡与湿位涡变化特征

Isentropic Potential Vorticity and Moist Potential Vorticity’s Variation Characteristics of Heavy Rain Caused by Rammasun in Guangxi

摘要: 本文运用NCEP/NCAR 1˚ × 1˚再分析资料，结合广西区域自动气象站降水资料，对超强台风“威马逊”(1409)引发广西暴雨天气的等熵位涡与湿位涡变化特征进行了分析，结果表明：此次台风暴雨是由东南气流带来的高温高湿水汽在台风外围强辐合上升作用下产生的对流性强降雨，水汽主要来自孟加拉湾、南海以及西太平洋。由等熵位涡分析可知，台风中心位涡值最大，高层位涡值大于低层位涡值。“威马逊”为强台风时，未来6 h暴雨中心位于位涡中心气流辐合处，其强度减弱为热带风暴后，未来6 h暴雨中心则位于位涡中心右侧。由湿位涡分析可知，“威马逊”暴雨中心多位于MPV₁ < 0区域内，对流层低层MPV1“上正下负”配置有利于暴雨的发生发展，台风中心与MPV₁大值中心对应。对流层低层MPV₂“上负下正”配置有利于降水的增幅，MPV₁ < 0且MPV₂ > 0的区域对未来6 h暴雨中心有较好的指示性，MPV₁ < 0且MPV₂ < 0叠加对于未来6 h降水有增幅效果，同样易出现暴雨中心。

Abstract: This paper aims at analyzing the variation characteristics of IPV and MPV of rainstorm in Guangxi, which is triggered by the super typhoon Rammasun (1409), by analyzing the precipitation data from automatic station in Guangxi area and reanalyzing the data of NCEP/NCAR (National Centers for Environment Prediction/National Center for Atmosphere Research). Isentropic potential vor-ticity (IPV) and moist potential vorticity (MPV) characteristics of the rainstorm in Guangxi are analyzed, which is triggered by super typhoon Rammasun (1409). The conclusions are as follows: The strong convection rainstorm weather is affected by warm and moist air convergence which contributes to the development of ascent movement. Water vapor is mainly transported from the Bay of Bengal, the South China Sea and the Western Pacific. The calculation of IPV shows that IPV from the upper layer is larger than the lower layer, and IPV of the typhoon center is the maximum. When Rammasun is strong typhoon, the rainstorm center locates at the center of the potential vorticity and airflow convergence in the next 6 hours; while Rammasun’s intensity decreases as tropical storm, the rainstorm center lies in the right side of the center of IPV in the next 6 hours. According to the results of the analysis of MPV, rainstorm center is likely to occur in negative MPV₁ region. It is advantageous to the development of rainstorm that MPV₁ is “positive at upper and negative at low” in the low troposphere. The center of typhoon has a very good correspondence with the center of big value of MP_V1. MPV₂, “negative at upper and positive at low”, is benefited for the increasing of precipitation in the low troposphere. When MPV₁ < 0 and MPV₂ > 0, the future rainstorm center will probably happen. Negative MPV₁ and negative MPV₂ are good for increasing of precipitation in the next 6 hours and also heavy rain center will happen.