Dynamical effects of internal gravity waves in the equinoctial thermosphere
Dynamical effects of internal gravity waves in the equinoctial thermosphere
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平分热层中内部重力波的动力学效应
DOI：
10.1016/j.jastp.2011.11.014
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发表时间：
2012
影响因子：
1.9
通讯作者：
P. Hartogh
中科院分区：
文献类型：
--
作者：
Erdal Yiğit;A. Medvedev;A. Aylward;A. Ridley;M. Harris;M. Moldwin;P. Hartogh
利用最近发展起来的谱非线性重力波(GW)参数化方法，首次研究了低层大气起源的广谱小尺度内部重力波对赤道热层的影响。GW在两个半球传播到F区高度，对平均纬向风产生明显的阻力。文中还模拟了GWS对两单体平均环流的修正。在中高纬度地区，平均纬向GW阻力与高达∼260公里的离子阻力相当。虽然GWS的平均动力效应是平均气流的减速，但瞬时GW体力可以同时具有这两个标志。在南半球高纬度地区，GW产生了大于1000ms−1day−的大扭矩，并对其产生的机理进行了详细的研究。GW各向异性在抵消和调制波滤波中起着至关重要的作用，为高纬度西风谐波提供了更有利的条件。由于分子粘度、热传导和离子阻力的增强，这导致了一个非常大的局部向东的GW阻力在高层热层达到最大。最后，给出了高空热层GW体力的高纬度分布，并与离子阻力作了比较。GW动量沉积表现出明显的半球差异和较大的纵向变化。
Using a recently developed spectral nonlinear gravity wave (GW) parameterization implemented into a 3-D coupled general circulation model, the effects of a broad spectrum of small-scale internal GWs of lower atmospheric origin on the equinoctial thermosphere are studied for the first time. GWs propagate to F region altitudes in both hemispheres, producing appreciable drag on the mean zonal wind. Some modifications of the two-cell equinoctial mean circulation by GWs are simulated, too. The mean zonal GW drag is comparable to the ion drag up to ∼260km in the middle- and high-latitudes. While the mean dynamical effect of GWs is the deceleration of the mean flow, the instantaneous GW body force can have both signs. In the Southern Hemisphere high-latitude, GWs are found to produce large torque of more than 1000ms−1day−1the mechanism of which is investigated in detail. GW anisotropy plays a crucial role in offsetting and modulating wave filtering, introducing increased favourable conditions for westerly harmonics in the high-latitudes. This leads to a very large localized eastward GW drag reaching a maximum in the upper thermosphere as a consequence of enhanced molecular viscosity, thermal conduction, and ion drag. Finally, the high-latitude distribution of the GW body force is presented in the upper thermosphere along with the comparison with ion drag. It demonstrates significant interhemispheric differences and large longitudinal variations in GW momentum deposition.