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

“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。

The distribution of spectrum point at baroclinic shear basic flow is analyzed in the paper entitled“ 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 continuous 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 continuous spectrum. In the overlapped 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 wave is slower than inertia gravitational waves.