Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe
Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe
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DOI：
10.1029/2019jd031662
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发表时间：
2020-03-16
影响因子：
4.4
通讯作者：
Jacobi, C.
中科院分区：
文献类型：
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作者：
Heale, C. J.;Bossert, K.;Jacobi, C.
2016 年 1 月 12 日在中欧观测到的强烈山浪在代表相反潮汐相位的两种固定背景风条件下进行了二维模拟。模拟的目的是研究山波的破裂以及随后在高层大气中产生的非初级波。模型结果显示，山波在接近中层临界水平时首先破裂，在 8-30 公里的水平尺度上产生湍流。这些湍流尺度直接耦合到水平次级波尺度，但潮汐风阻止这些尺度到达热层，潮汐风起到过滤器的作用。能够到达热层的初始次级波水平尺度范围为60~120 km，受山波纬向相位宽度波破碎相关的水平和垂直强迫尺度以及水平波长尺度的影响。大尺度非主波在整个模拟过程中占主导地位，水平尺度为 107-300 公里，周期为 11-22 分钟。热层风严重影响热层中波浪强迫的时间平均空间分布，其峰值在150公里高度，并且在2个UT背景模拟中发生在源的西边和东边，在7个UT背景模拟中主要发生在源的东边。强迫幅度约为原始山浪破碎消散幅度的2倍。这表明非主波在重力波动力学中发挥着重要作用，并且提高对热层风的理解对于理解其强迫分布至关重要。
A strong mountain wave, observed over Central Europe on 12 January 2016, is simulated in 2D under two fixed background wind conditions representing opposite tidal phases. The aim of the simulation is to investigate the breaking of the mountain wave and subsequent generation of nonprimary waves in the upper atmosphere. The model results show that the mountain wave first breaks as it approaches a mesospheric critical level creating turbulence on horizontal scales of 8-30 km. These turbulence scales couple directly to horizontal secondary waves scales, but those scales are prevented from reaching the thermosphere by the tidal winds, which act like a filter. Initial secondary waves that can reach the thermosphere range from 60 to 120 km in horizontal scale and are influenced by the scales of the horizontal and vertical forcing associated with wave breaking at mountain wave zonal phase width, and horizontal wavelength scales. Large-scale nonprimary waves dominate over the whole duration of the simulation with horizontal scales of 107-300 km and periods of 11-22 minutes. The thermosphere winds heavily influence the time-averaged spatial distribution of wave forcing in the thermosphere, which peaks at 150 km altitude and occurs both westward and eastward of the source in the 2 UT background simulation and primarily eastward of the source in the 7 UT background simulation. The forcing amplitude is similar to 2 x that of the primary mountain wave breaking and dissipation. This suggests that nonprimary waves play a significant role in gravity waves dynamics and improved understanding of the thermospheric winds is crucial to understanding their forcing distribution.