斜压气流的中尺度稳定性 Ⅰ.对称不稳定

本文是“斜压气流的中尺度稳定性”的第一部份,讨论斜压基流对平行型中尺度扰动的稳定性,寻找弱稳定层结大气中出现带状中尺度扰动的可能性及其对深厚对流云系的启动和组织作用。 用非弹性近似(anelastic assumption),导出适于用广义矩阵法及打靶法解特征值问题的理想大气扰动方程,并在线性风,双曲正切型风及飑线发生前的实测风分布下,计算出中尺度不稳定谱及特征扰动结构,通过能量分析,说明斜压性在产生这种非地转惯性对流中的作用。

ON MESOSCALE INSTABILITY OF A BAROCLINIC FLOW 1. Symmetric Instability

The first part of the present work investigates instability of a baroclinic basic flow against the mesoscale disturbances parallel to it. The focus of this study is to search for the possibility for a mesoscale disturbance of band structure to occur in a stably stratified atmosphere and its effect on triggering and organizing deep convections,The two- and three-dimensional perturbation equations, suitable to solving eigenvalue problems by use of the generalized matrix method and shooting method, are formed under anelastic approximation. The criteria for symmetric instability to set in are discussed for a linear, a hyperbolic-tangential and a real wind profile sounded before occurrence of a squall line event in SESAME 1979. The effect of baroclinicity of the basic flow on occurrence of this kind inertial convection is also analyzed in terms of energetic calculation.