湿斜压性与热带气旋强度突变

应用湿位涡方程和倾斜涡度发展理论 ,研究了热带气旋内部相当位温结构的演变与其强度突变的可能关系 ,并用一套高分辨率的模拟资料对所得结论进行验证。结果表明 ,由于热带气旋眼壁附近等相当位温面陡立 ,湿斜压性变化所激发的倾斜涡度发展是引起该区域垂直涡度突然增大或突然减小的主要原因。当热带气旋中心附近大部分区域的垂直涡度显著增长时 ,热带气旋就会在整体上表现为爆发性或迅速发展。最后还据此对同心双眼结构的出现和消失如何影响热带气旋强度变化进行了探讨。

MOIST BAROCLINITY AND ABRUPT INTENSITY CHANGE OF TROPICAL CYCLONE

Based on MPV equation and the theory of slantwise vorticity development, the possible relationship between the abrupt intensity change of tropical cyclone and the evolution of its equivalent potential temperature structure is studied in this paper. A set of high resolution model output data is used to verify the result. Analyses show that, because the moist isentropic surfaces are extremely steep in the eyewall region, the change of moist baroclinity is a main cause for abrupt change of vertical vorticity there. If the vertical vorticity increases rapidly in most regions, the tropical cyclone will experience explosive deepening. Some discussions on how the concentric eyewall structure affects the intensity of tropical cyclone are also proposed.