用传输函数构建的大气重力波传播理论模式

本文根据考虑大气热传导和黏滞的重力波复色散关系，采用传输函数的概念，基于重力波的线性理论，构建了用于研究对流层内重力波激发源与电离层响应之间的传输函数数值模式.在相空间中讨论了传输函数振幅的分布特性，并以地面单位脉冲源为例，分析了从地面到300 km高空的响应，得到了物理量的时空分布特征.结果表明：（1）对内重力波的传播而言，大气相当于一个滤波器，只有波动周期在15～30 min，水平波长在200～450 km之间的重力波扰动才最容易到达300 km电离层高度；（2）电离层的响应主要在与地面的激发源之间相隔较远的水平距离上发生；（3）黏滞和热传导系数在低层对上传重力波的影响较小，随着高度的增加它们对重力波的影响越来越大；（4）在低层计算的波动频率与Row理论的计算结果比较一致，然而到了高层却相差较大.

A theoretical model of gravity wave propagation based on the transfer function

In order to study the relationship between the excitation source of gravity wave in the troposphere and the response of ionosphere,a theoretic model of gravity wave propagation based on the complex dispersion relation of internal gravity wave and the conception of transfer function has been built in a dissipative atmosphere which includes viscosity and heat conductivity.In the paper the amplitude of transfer function is discussed in the frequency domain.Through analyzing a case of unit impulse,we obtain the distribution of a certain physical quantity in time and space from earth's surface to 300 km above.The results reveal that the atmosphere behaves like a filter which offers the easy passage to some gravity waves whose periods range from 15 min to 30 min and the horizontal wave lengths are between 200 km and 450 km.The response of ionosphere occurs at a large horizontal distance from the source.The viscosity and the conductivity coefficients of atmosphere have small influence in the low atmosphere,but it becomes greater with increasing of height.The frequency obtained by the transfer function model is consistent with that from Row's theory in the low atmosphere,but they differ much in the high atmosphere.