耗散大气中水平不均匀风场对内重力波传播的影响

THE EFFECT OF INHOMOGENEOUS WINDS ON INTERNAL GRAVITY WAVE PROPAGATION IN A DISSIPATIVE ATMOSPHERE

采用包括耗散的射线跟踪方法 ,计算了在水平不均匀风场作用下 ,不同尺度重力波从对流层直至 2 2 0km观测高度的传播 ,结果表明 ,垂直于重力波传播方向的风以及风剪切能够引起波射线的折射 ,从而导致重力波明显偏离初始传播方向 .在强顺风场作用下 ,由于风场引起的捕获 ,大量重力波不能传播到观测高度 .由于风场引起的多普勒频移 ,小周期的重力波在弱顺风条件下能够传播到观测高度 .由于反射作用 ,强逆风场不支持周期低于约1 8min的较高频重力波的传播 .而在弱逆风作用下 ,大部分中尺度范围重力波都能够传播到观测高度 .本文统计了武汉电离层观象台的TID观测数据随热层风场的分布 ,统计结果与模拟结果符合较好 .

Ray tracing method is used to calculate the propagation of gravity waves with various period and wavelength from ground to the observation height of 220km in a dissipative atmosphere. The results show that the refraction caused by wind and wind shear vertical to the propagation direction leads to considerable changes of wave propagating direction. Under the condition of propagating along strong wind,large number of waves cannot reach the observation height,due mainly to critical coupling. While under the condition of propagating along weak wind,waves with short period can reach observation height,due to dopler shift of wave frequency. Under the condition of propagating against strong wind,waves with period less than 18min cannot reach observation height,for they are reflected below thermosphere. And under the condition of propagating against weak wind,most of medium-scale gravity waves can reach observation height. The Travelling Ionosphere Disturbances (TIDs) observed by Wuhan Ionosphere Observatory is statistically analyzed. The distribution of TIDs with thermosphere wind is in agreement with the numerical results.