一次入海气旋快速发展的动力和热力学特征分析

Dynamic and Thermal Analyses on an Rapidly Developing Extratropical Cyclone after Entering Sea

利用扩展Zwack-Okossi方程(扩展Z-O方程)对2007年3月3-5日黄、渤海海上快速发展的温带气旋进行了诊断分析。结果表明,潜热释放和暖平流在气旋发展初期起主要作用,潜热释放是气旋接近爆发性发展的最主要强迫项,这与以往研究的主要受涡度平流强迫的中国沿海温带气旋不同,说明在中国近海快速发展的一部分温带气旋主要是由潜热释放项强迫的。绝对涡度平流在气旋发展后期才成为主要强迫项。进一步利用MM5模式模拟了潜热释放的作用以及其他一些影响气旋发展的因素,海表面热通量、水汽通量以及气旋路径上的地形对这次气旋的发展有积极贡献,但作用相对潜热释放较小。由于这种在中国近海接近爆发性发展的温带气旋容易造成风暴潮,因此利用动能方程对气旋发展中期的渤海大风进行了诊断分析。结果表明,动能水平平流是动能增加的主要作用项,但动能达到最大值后渤海海域的动能主要由有效位能转换和动量下传提供。

An extratropical cyclone which rapidly developed in the Yellow Sea and Bohai Sea on 3-5 March 2007 is diagnostically analyzed by the extended Zwack-Okossi equation. Results show that latent heat release and horizontal warm-air advection are main forcing terms at the early developing stage, and la- tent heat release is mostly responsible for the almost explosive development of the cyclone, while hori- zontal absolute vorticity advection become the main forcing term at the late developing stage. Cold-air ad- vection which is the dominant weakening term during the weakening stage of the cyclone and adiabatic cooling act as weakening the cyclone during the whole period. The surface sensible and latent heat fluxes contributed little to the development of the cyclone, with the negative contribution in Yellow Sea and Bo- hai Sea and the positive contribution in Japan Sea. The surface moist flux played more important role than the surface sensible and latent heat fluxes do in the development of cyclone. Changbai Mountain and Kore- an Mountain also are favorable for the development of cyclone by intensifying the precipitation and the la- tent heat. The cyclone resulted in a storm surge in Bohai Sea, so the gale in Bohai Sea by kinetic energy e- quation is analyzed. The results show that the increase of kinetic energy in Bohai Sea resulted from hori- zontal kinetic energy advection before 20..00 on 4 March 2007, with smaller contributions from available potential energy exchange and downward momentum transport. After 20：00, the kinetic energy in Bohai Sea was supplied by available potential energy exchange and downward momentum transport. The contri- bution of downward momentum transport was equal to that of available potential energy exchange, and sometimes larger than that of available potential energy exchange.