非热成风平衡基流的对称不稳定

SYMMETRIC INSTABILITY OF NON THERMAL WIND BALANCE BASIC FLOW

采用适合于中尺度研究的ｆ平面、非静力平衡、滤声波模式，运用解析方法研究了具有非热成风梯度存在的高空急流入口区右侧及低空急流入口区左侧的对称不稳定性问题。求出了扰动流函数解析表达式，从而定性地分析了由于非热成风梯度的存在，中尺度扰动波结构以及波振幅空间分布特征。通过解析求解得到了扰动半波长Ｌｃ及非热成风梯度存在时的对称不稳定判据。所得理论结果可以解释在平行型高低空急流入口区之间产生强暴雨的原因。

Symmetric instability is analytically investigated of the right side of upper air jet entrence region and the left side of lower level jet entrance region with non thermal wind gradients available in the context of a f plane, non hydrostatic equilibrium and acoustic wave filtering model for meso scale research purposes, arriving at an analytic expression of perturbation streamfunction, whereby qualitative analysis is done of the existence of non thermal gradients, meso perturbation wave structure and spatial distrbution features of wave amplitude. And obtained analytically are the disturbance half wave length L c and criterion for symmetric instability with non thermal gradients available. Results presented can account for causes of vigorous rainstorm genesis at jet entrance regions one atop the other at high and lower levels.