Mesospheric Mountain Wave Activity in the Lee of the Southern Andes
Mesospheric Mountain Wave Activity in the Lee of the Southern Andes
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DOI：
10.1029/2020jd033268
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发表时间：
2020-06
期刊：
影响因子：
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通讯作者：
P. Pautet;M. Taylor;D. Fritts;D. Janches;N. Kaifler;A. Dörnbrack;J. Hormaechea
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文献类型：
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作者：
P. Pautet;M. Taylor;D. Fritts;D. Janches;N. Kaifler;A. Dörnbrack;J. Hormaechea
由地形强迫产生的重力波（GW），也称为山波（MW），已经被研究了数十年。首先在对流层进行测量，然后在平流层进行测量，直到 2008 年才在中层高度拍摄到它们的图像。在最近的几次观测活动中对它们的特征进行了研究，但关于它们对高层大气的影响以及背景环境对其深层传播的影响，仍然存在许多问题。 2018 年南方冬季，先进中层温度测绘仪 (AMTM) 和阿根廷南部敏捷流星雷达 (SAAMER) 在阿根廷里奥格兰德（南纬 53.8°）同时运行。该站点位于南美洲尖端附近，安第斯山脉的背风处，该地区被认为是地球上最大的兆瓦热点地区（例如，Eckermann & Preusse，1999；Hendricks 等，2014；Jiang 等，2003、2005、2002；Wright 等，2016）。 6 个月期间获得的新 AMTM 图像数据显示，近 100 次 MW 特征渗透到上层中间层。在冬季中期（五月中旬至七月中旬）期间，大约 30% 的时间都可以看到它们。它们的间歇性与半日潮控制的纬向风高度相关，揭示了大气背景对MW渗透到中间层低层热层（MLT，海拔80-100公里）的直接影响。其动量通量 (MF) 的测量结果被确定达到非常大的值（36 个事件的平均值~250 m2/s2），为中层高度小尺度重力波的重要性和影响提供了有力的证据。
Gravity waves (GWs) generated by orographic forcing, also known as mountain waves (MWs) have been studied for decades. First measured in the troposphere, then in the stratosphere, they were only imaged at mesospheric altitude in 2008. Their characteristics have been investigated during several recent observation campaigns, but many questions remain concerning their impacts on the upper atmosphere, and the effects of the background environment on their deep propagation. An Advanced Mesospheric Temperature Mapper (AMTM) and the Southern Argentina Agile MEteor Radar (SAAMER) have been operated simultaneously during the Austral winter 2018 from Rio Grande, Argentina (53.8°S). This site is located near the tip of South America, in the lee of the Andes Mountains, a region considered the largest MW hotspot on Earth (e.g., Eckermann & Preusse, 1999; Hendricks et al., 2014; Jiang et al., 2003, 2005, 2002; Wright et al., 2016). New AMTM image data obtained during a 6‐month period show almost 100 occurrences of MW signatures penetrating into the upper mesosphere. They are visible ∼30% of time during the period corresponding to the middle of the winter season (mid‐May to mid‐July). Their intermittency is highly correlated with the zonal wind controlled by the semi‐diurnal tide, revealing the direct effect of the atmospheric background on MW penetration into the mesosphere lower thermosphere (MLT, altitude 80–100 km). Measurements of their momentum fluxes (MFs) were determined to reach very large values (average for 36 events ∼250 m2/s2), providing strong evidence of the importance and impacts of small‐scale gravity waves at mesospheric altitudes.