Andes上空中间层和低热层中大气惯性重力波的激光雷达观测

利用Andes观测站(30. 3°S,70. 7°W)激光雷达2016年6月8～9日共11. 6 h的风场、温度以及钠原子数密度的观测数据,研究了一个在中间层顶区域惯性重力波活动事件。谱分析表明,这个惯性重力波的周期约6. 6 h,垂直波长约7. 5 km,水平波长约826 km。根据矢端曲线法分析发现,此惯性重力波的传播方向大约为西偏北38. 6°。计算出它的垂直群速度约0. 2 m·s~(-1),水平群速度约22. 9 m·s~(-1)。射线追踪结果表明,上传惯性重力波可能来自于平流层的急流区域。虽然该惯性重力波不能达到不稳定性的阈值,但是理查德森数和浮力频率显示,由于不同扰动分量的叠加,导致了在一些高度和时间上,动力学的发生和对流不稳定性的存在。因此,叠加效应引起的不稳定性可能会对中间层-低热层中波的饱和度和幅度约束有显著影响。同时利用重力波偏振关系和惯性重力波纬向风扰动,计算出了经向风、温度和大气密度扰动,同时观测的经向风和温度扰动与计算的结果一致,表明观测到的准单色惯性重力波能很好满足重力波偏振关系。另外,计算得到的大气密度扰动与观测的钠原子数密度扰动相位一致,证实了中间层-低热层区域的钠原子可以作为重力波的示踪物。

A case study of inertia gravity wave event based on Na lidar observation

Using the 11.6 h wind, temperature and Na atom number density data observed by the Na lidar system at Andes Lidar Observatory (30.3°S,70.7°W) from 2212 UT 8 June to 1024 UT 9 June 2016, we study a typical upward propagating inertia-gravity wave (IGW) in the mesosphere and lower thermosphere (MLT). The spectral analysis indicates that the period of the IGW is about 6.6 h, and its horizontal and vertical wavelengths are about 826 km and 7.5 km, respectively. Hodograph technique shows that the wave propagates in the horizontal direction of about 38.6° west of north. The horizontal and vertical group velocities are calculated to be 22.9 ms-1 and 0.2 ms-1, respectively. The ray-tracing analysis indicates that the upward propagating IGW probably originates from the stratospheric unbalances flow over the Antarctic. Although the IGW do not reach the threshold of instability,However, the Richardson number and N2 show the occurrence of dynamical and convective instabilities in some height and time due to the superposition of different perturbation components. Hence, the instability arising from the superposition effect may have a significant influence on wave saturation and amplitude constraint in the MLT. According the IGW polarization relations, the perturbation components of the meridional wind, temperature and atmospheric density are derived from the zonal wind perturbation. The observed perturbations in the meridional wind and temperature are consistent with the results derived from the polarization relations, which indicates that the observed quasi monochromatic IGW satisfies the polarization relations of GWs. The calculated perturbation phase of Na atom number density is in good agreement with that of atmospheric density, confirming that the Na atom in the MLT can be regarded as a tracer of IGW activity.