斜压切变基流中横波型扰动的特征波动 Ⅱ:谱函数
CHARACTERISTIC WAVES OF TRANSVERSAL DISTURBANCE AT BAROCLINIC SHEAR FLOW Ⅱ:SPECTRAL FUNCTION
-
摘要: “斜压切变基流中横波型扰动的特征波动:谱点分布”一文中分析了斜压切变基流中横波型扰动的谱点分布,这里又对其谱函数进行了分析讨论。结果表明:当基流在垂直方向存在切变时,重力惯性波与涡旋波的谱函数在垂直方向上均可出现临界层,临界层的高度随频率σ而变化,即重力惯性波与涡旋波都存在连续谱,但涡旋波与重力惯性波连续谱的结构却不同;对天气尺度扰动,两支重力惯性波和1支涡旋波的连续谱不重叠,此时每支波动仅有1个临界层;而对次天气尺度的扰动,重力惯性波与涡旋波的连续谱区会发生重叠,在连续谱的重叠区,重力惯性波仍只有1个临界层,但涡旋波则可以有2个或3个临界层。无论是涡旋波还是重力惯性波其连续谱的波包随时间都是衰减的,但涡旋波波包比重力惯性波波包衰减得慢。Abstract: The distribution of spectrum point at baroclinic shear basic flow is analy zed in the paperent it led "characteristic waves of tranversal disturbance at baroclinic shear flow Ⅰ:spectrum analysis". The spectral function is studied there. The results show that, when the vertical shear of basic flow is not zero, there is a critical layer in the vertical direction about the spectral function of inertia-gravitational wave and vortex wave. The height of critical layer is changing with frequency. The continuo us spectrum structure of vortex wave is different from that of inertia-gravitational wave.To synoptic scale disturbance, the continuous spectrum of them is not overlapped, and there is only a critical layer to every wave. To subsynoptic scale disturbance, there exists overlap of wave continuo us spectrum. In the overl apped spectrum area, there is still a critical layer to the inertia-gravitational wave, but there are two or three critical layers to vortex wave. Not only vortex wave but also inertia-gravitational waves, the wave ensemble is decaying with time, the decay of vortex waveis slower than inertia-gravitational waves.