双变量波状扰动激发重力波波包的数值研究

采用谱配置方法对双变量波状扰动激发重力波的过程及其能量传播和转换特性进行数值研究．模拟结果表明，当初始给定的两个变量的波状扰动的相对振幅和相位严格满足重力波的偏振关系时，只有水平风场扰动(u′)与温度扰动(7′)的共同作用才能抑制能量向下传输．通常情况下，两个变量的波状扰动都会激发出两文传播方向相反的重力波波包，这两支波包的相对能量明显取决于两个波状扰动之间的相对振幅关系．当两个扰动之间的相对振幅满足特定条件时，向下传播的能量几乎为零，只会有一支向上传播的重力波波包被激发．进一步的数值分析则表明，各种情况下两个变量的波状扰动所激发的重力波波包的能量传播路径和速度基本相同；与单变量波状扰动激发重力波波包的过程相比，能量传播路径几乎完全一致，扰动转化为波动的特征时间也基本相同，但能量转换效率更高．

A NUMERICAL STUDY ON THE GRAVITY-WAVE PACKETS EXCITED BY TWO-VARIABLE WAVE-LIKE DISTURBANCES

By using the spectral allocation method, the energy propagation and the characteristics of energy conversion in the excitation of gravity waves by initially given two-variable wave-like disturbances is numerically studied. The simulation results show that when the relative amplitudes and phases of the two initially given wave-like disturbance variables satisfy strictly the polarization relation of gravity waves, only this two-variable disturbance which variables are horizontal wind and temperature can restrict the downward energy propagation of gravity waves. In general cases, A two-variable wave-like disturbance will excite two gravity-wave packets, one propagates upward and the other downward, moreover, the ratio of wave energy for those two gravity waves is decided evidently by the relation of the amplitudes for the two initial disturbance variables, when the ratio satisfies certain condition, only one upward propagating gravity wave can be excited. Further numerical analysis shows that, both the energy propagation paths and velocities in all numerical cases are identical with each other. Compared with the results of energy conversion for gravity waves excited by single-variable disturbances, the characteristic times of the energy conversion for gravity waves in the cases present in this paper are the same, but the efficiencies of energy conversion are larger.