水平切变线上涡层不稳定理论

THE INSTABILITY OF THE VORTEX SHEET ALONG THE HORIZONTAL SHEAR LINE

文中打破了传统的 Kelvin- Helmholtz研究切变不稳定的观点 ,考虑了强涡度切变存在时切变线已构成了一个涡层 ,这时切变线的不稳定问题就变为涡层的不稳定问题。同时考虑由涡层所产生的诱导速度 ,从理论上得到了水平切变线上涡层不稳定必要条件的判据 ,即必须满足 (1 - Rv+Rid) >0 ,且有 U(y,t) >U(A(t) )与之相配合。这表明环境场的配置制约着切变线上扰动的发展 ,这种中尺度扰动同环境场存在着相互作用。文中还用具体个例对如何计算不稳定必要条件做了解释和说明。

The traditional Kelvin Helmholtz notion of studying the shear instability is not suitable to the shear line with the strong horizontal wind shear. For this case, the shear line should be considered as the vortex sheet. Since then, the instability of this kind of the shear line becomes the instability of the vortex sheet rather than the traditional shear instability. If the velocity is induced by the vortex sheet, the in equalities, (1-R v+R id )>0 and U(y,t)> U(A(t)) become the criterion of the vortex sheet instability. This criterion indicates that the disposition of environment field restrains the disturbance developing along the shear line,there exist multi scale interactions between this mesoscale disturbance and environment field. The calculation of the necessary condition for the instability is also presented in this paper.