Propagation Characteristics of Gravity Waves Around Critical Layers Revealed by the Andes Lidar

IF 2.9 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
Ming Yu Hu, Shao Dong Zhang, Chun Ming Huang, Yun Gong, Kai Ming Huang, Zheng Ma
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Abstract

By analyzing horizontal wind and temperature data from the Andes Lidar Observatory Na lidar at Cerro Pachón, Chile (30.3°S, 70.7°W) from May 2014 to July 2019, we investigated the evolution process, propagation characteristics, and influencing factors of gravity waves (GWs) encountering the critical layer. Adopting the criterion that the critical layer is observed when the intrinsic frequency reaches 1.3 times the inertial frequency, accompanied by a sharp decrease in vertical wavelength, we identified 40 critical layer events, with an occurrence rate of 58.9%, indicating that critical layers are common phenomena in the MLT of the Andes mountain area. All observed GWs encountering the critical layer propagate along the wind, with rapid decreases in vertical wavelength and energy and momentum absorption by the background. When the critical layer appears, 44.2% of the wave energy is below 20 J/kg, and 30.4% of momentum flux is below 50 m2/s2. Contrary to the predictions of linear theory, not all waves are fully absorbed at the critical layer. Some carry residual energy to higher altitudes until reaching a second (19.1%) or third (4.4%) critical layer. These effects must be considered in the future GWs parameterization models. The occurrence rate of critical layers shows significant seasonal and altitude variations, being higher in autumn and lower in summer, mainly at 90–91 km, influenced by background wind and thermal structure. The critical layer usually forms below the mesopause, and its occurrence is negatively correlated with mesopause altitude, as a smaller buoyancy frequency favors its formation.

安第斯激光雷达揭示的关键层周围重力波传播特性
利用2014年5月至2019年7月智利Cerro Pachón(30.3°S, 70.7°W)安第斯激光雷达Na激光雷达的水平风和温度数据,研究了遇到临界层的重力波的演化过程、传播特征及其影响因素。采用本征频率达到惯性频率1.3倍时出现临界层,且垂直波长急剧下降的判据,共识别出40个临界层事件,发生率为58.9%,说明临界层是安第斯山区MLT中常见的现象。所有观测到的遇到临界层的gw都沿风传播,垂直波长和背景吸收的能量和动量迅速减少。当临界层出现时,44.2%的波能低于20 J/kg, 30.4%的动量通量低于50 m2/s2。与线性理论的预测相反,并非所有的波都在临界层被完全吸收。有些将剩余能量带到更高的高度,直到到达第二层(19.1%)或第三层(4.4%)临界层。在未来的GWs参数化模型中必须考虑这些影响。受背景风和热结构的影响,临界层的出现率呈现出明显的季节和高度变化,秋季较高,夏季较低,主要分布在90 ~ 91 km。临界层通常形成于中层顶以下,其出现与中层顶高度呈负相关,浮力频率越小越有利于其形成。
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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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