登陆台风等熵面位涡演变的数值模拟研究

选取1997年第11号台风温妮为研究个例,通过中尺度模式MM5模拟再现了该台风登陆后经历初期减弱、变性及变性后再次发展的演变过程.引入Ertel等熵面位涡收支方程,深入分析了登陆台风结构演变的过程中绝热与非绝热作用对对流层低层位涡局地变化的影响.研究表明:台风温妮深入内陆的过程中,对流层低层台风中心西北侧位涡增长,且大值中心不再与台风中心重合;由于摩擦和非绝热加热的存在,对流层低层位涡不守恒,其局地变化主要决定于位涡的水平平流(守恒项)、位涡的垂直平流、加热的垂直微分(非守恒项)的分布;台风温妮变性前后,对流层低层位涡的守恒性逐渐减弱,非守恒项尤其是加热的垂直微分对位涡的局地增长的正贡献不断增强直至占有主导地位.

Numerical Simulation of the Evolvement of Potential Vorticity of Landfall Tropical Cyclone on Isentropic Surface

The maintenance process of typhoon Winnie (1997) after landfall was reappeared by using the MM5 model. The numerical simulations cover the entire process including initial weakening, extratropical transition and redeveloping. The adiabatic and diabatic effect on the local change of potential vorticity (PV) at lower troposphere was analyzed, during the entire process using Ertel potential vorticity budget equation on isentropic surface. The results show that the PV increases in the west and north of tropical...