热带气旋过程中的近惯性振荡解及频散关系

Upper Ocean Near-inertial Oscillations and Dispersion Relation in the Course of Tropical Cyclone

基于简单的Slab模式,建立了热带气旋过程中上层海洋近惯性流与风应力之间的定量关系。在此基础上推导出了近惯性振荡在海面能量输入通量及在温跃层内能量耗散表达式,揭示了近惯性流在大尺度准地转流场作用下的频散关系。研究表明:上混合层近惯性流的产生是局地风应力直接作用的结果。海洋因其层化效应存在相应的斜压正交模,当风应力频率与海洋内部固有的斜压模态相近时,二者共振产生近惯性振荡。而当海面输入近惯性能量大于其在上混合层能量损耗的水深平均值时,近惯性振荡处于增长阶段,反之则处于衰减阶段。大尺度准地转流的作用是对近惯性振荡流产生频移效应,而对近惯性流的能量耗散没有贡献。

The quantitative relationship between the upper ocean near-inertial current and the local wind stress and the expressions of near-inertial energy input at the surface and the energy dissipation within the thermocline in the course of a tropical cyclone are investigated based on a simple slab model. It is indicated that the near-inertial oscillations in the ocean mixed layer are created by the local wind stress. As the wind stress changes with the baroclinic model of the interior ocean, the resonance mechanism is expected to oc- cur in the upper layer. Additionally, the near-inertial oscillations are amplified （or damped） with time when the near-inertial energy input at the surface is greater （or smaller） than the average energy dissipation in the mixed layer. The quasi-geostrophic flow has no effect on the energy dissipation in the mixed layer, but has an effect on the frequency shift of the near-inertial current.