内重力波传播的3维传输函数模式研究

Study of Internal Gravity Waves Propagation on the Basis of the Three-Dimensional Transfer Function Model

在考虑背景风场及大气耗散的条件下,建立了3维内重力波传输函数数值模式．分析了300km高度3维传输函数在频率波数域的特性,并以近地面单位脉冲点源为激发源,得到了内重力波在3维空间中的时空分布．讨论了不同时空尺度地面方波源激发的内重力波在电离层高度的能量分布特征．结果表明, (1)对内重力波而言,背景大气相当于一个带通滤波器,只有波动周期和波长分别在15～30 min和200～400 km之间的重力波扰动最容易上传到300 km高度;(2)在背景风场的作用下水平面上以同心圆扩散的波阵面以及垂直方向上成漏斗状的波阵面发生了变形,并且逆风方向比顺风方向更有利于声重力波由对流层向电离层高度传播;(3)300km高度对时间尺度和空间尺度分别在20～30 min和150～250 km之间的地面方波源响应的总能量最强．

In this paper the three-dimensional transfer function model has been developed in the atmosphere with dissipation and background winds. Then the model is used to analyze the filter characteristics in the frequency wavenumber domain and the spatial-temporal domain. Finally, we discussed the total energy of ionosphere response on the three rectangle waves with the different spatial-temporal scales on the surface. The computed results reveal that for internal gravity waves, the atmosphere behaves like a filter which only offers the easy passage to some gravity waves with periods of 15-30 min and with horizontal wave lengths of 200-400 km. The wave fronts which are like funnels in vertical profile and concentric circles in horizontal plane are distorted by the background winds when the gravity waves propagate from the earth surface to the ionospheric height. The gravity waves propagating against winds are easier than those propagating along winds. The total energy of ionosphere response can arrive at maximum when rectangle wave source＇s spatial scale is between 150km to 250km and temporal scale is between 20min to 30min.