西北太平洋爆发性气旋的诊断分析

A DIAGNOSTIC STUDY OF AN EXPLOSIVELY DEEPENING OCEANIC CYCLONE OVER THE NORTHWEST PACIFIC OCEAN

本文对一年中26个西北太平洋爆发性气旋形成的大尺度条件做了统计研究。结果表明:海洋上空大气层结的不稳定、高空急流出口区北侧的动力辐散,冬季副高位置偏北时其西侧的强暖平流以及中低层的强斜压区等都是气旋急剧发展的有利因素。 另外,本文利用完全的ω-方程和Sawyer-Eliassen次级环流方程对1983年1月6—9日发生在西北太平洋上的一次爆发性气旋做了诊断分析,得到:(1)大尺度加热是使气旋强烈发展的主要物理因子;积云对流加热也是重要的物理因子。(2)温度平流是使前两者起作用的先决因子,它对气旋的初期发展起了某种启动作用。

The vertical motions and secondary circulation of an explosively deepening oceanic cyclone, which occured over the Northwest Pacific Ocean and was in conjunction with 200 hPa-level jet stream and has central pressure falls of 33.9 hPa/24h, have been computed from seven-level nonliner balance model and Sawyer-Eliassen-Shapiro Equation for the transverse ageostraphic circulation. The vertical motions are partitioned into contributios from large scale latent heat release, effects of cumulus heating, thermal advection, differential vorticity advection and so on, while the secondary circulation stream function is partitioned into contributions from geostraphic deformation, transfer of momentum and heat in the area of cumulus and diabalic heating. The principal results are the following: large scale latent heat release is very crucial to explosive development of cyclone. If there is enough transfer of moisture, the positive feed-back process between ascent of air and large scale heating would work. The cumulus heating and the transfer of momentum and heat in the area of cumulus played an important role during the explosively deepening stage. Thermal advection is the initial triggering condition for large scale heating and the conditional instability for the convection of cumulus.