The Influence of Gravity Waves on the Slope of the Kinetic Energy Spectrum in Simulations of Idealized Midlatitude Cyclones
The Influence of Gravity Waves on the Slope of the Kinetic Energy Spectrum in Simulations of Idealized Midlatitude Cyclones
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DOI：
10.1175/jas-d-18-0329.1
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发表时间：
2019-06
影响因子：
3.1
通讯作者：
M. Menchaca;D. Durran
中科院分区：
文献类型：
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作者：
M. Menchaca;D. Durran
利用理想化的斜压不稳定切变流中气旋生长的模拟，研究了地面应力和地形产生的重力波对大气动能谱的影响。即使在地形的情况下，表面应力大大提高了在冷锋附近的重力波的产生，与这些波相关的垂直能量通量产生显着变浅的KE光谱在中尺度波长相对于相应的自由滑动的情况下。然而，单个孤立脊的影响比表面应力的影响显著得多。当山波发展得很好时，它们在平流层低层产生的波数在中尺度波长的宽范围内为−5/3。在对流层中部，一个较小的波长范围也呈现出-5/3光谱。当山高500米时，波不会破碎，它们的KE完全与速度场的发散分量有关，速度场的发散分量几乎随高度而恒定。当山是2公里高，波破碎产生的位涡，和KE谱的旋转分量也被强烈激发的波。分析的频谱KE预算表明，实际的频谱是不断移动的平衡的直接强迫垂直能量通量的发散，保守的平流输送，浮力通量的结果。然而，有一个有趣的例子，其中-5/3斜率的平流层下部能谱似乎与重力波引起的高惯性级联有关。
The influence of gravity waves generated by surface stress and by topography on the atmospheric kinetic energy (KE) spectrum is examined using idealized simulations of a cyclone growing in baroclinically unstable shear flow. Even in the absence of topography, surface stress greatly enhances the generation of gravity waves in the vicinity of the cold front, and vertical energy fluxes associated with these waves produce a pronounced shallowing of the KE spectrum at mesoscale wavelengths relative to the corresponding free-slip case. The impact of a single isolated ridge is, however, much more pronounced than that of surface stress. When the mountain waves are well developed, they produce a wavenumber to the −5/3 spectrum in the lower stratosphere over a broad range of mesoscale wavelengths. In the midtroposphere, a smaller range of wavelengths also exhibits a −5/3 spectrum. When the mountain is 500 m high, the waves do not break, and their KE is entirely associated with the divergent component of the velocity field, which is almost constant with height. When the mountain is 2 km high, wave breaking creates potential vorticity, and the rotational component of the KE spectrum is also strongly energized by the waves. Analysis of the spectral KE budgets shows that the actual spectrum is the result of continually shifting balances of direct forcing from vertical energy flux divergence, conservative advective transport, and buoyancy flux. Nevertheless, there is one interesting example where the −5/3-sloped lower-stratospheric energy spectrum appears to be associated with a gravity-wave-induced upscale inertial cascade.