中尺度扰动不稳定的数值研究

A Numerical Study of Instability of the Mesoscale Perturbation

利用一个二维Boussinesq流体的绝热无粘非静力数值模式 ,将中尺度不稳定问题作为一个初值问题进行数值研究。线性情况下数值试验的结果基本与采用特征值方法研究得到的结论一致。非线性情况的数值试验表明 ,其不稳定发生的范围可与线性情况不一致 ;非线性不稳定的增长率一般较线性不稳定的增长率要小 ;非线性作用会造成波型的陡凸 ,从而造成流函数正负环流的不对称和环流流线的密集 ;非线性情形下的流型有些与强对流系统的流型相像。

A non-hydrostatic, adiabatic and non-viscous two-dimensional Boussinesq model is used to study mesoscale instability. This paper discusses the mesoscale instability problem as an initial-value problem by numerical experiments.The results of linear numerical experiments are consistent with ones in using eigenvalue method.The results of non-linear numerical experiments show that the areas of non-linear instability differ from ones of linear instability. The growth rates of non-linear instability are less than ones of linear instability. The non-linear effects can make abrupt wave pattern, accordingly can bring non-symmetry of stream function and high concentration of streamline. The some stream function of non-linear conditions is similar to ones in heavy convection systems.