Nonlinear forcing mechanisms of the migrating terdiurnal solar tide and their impact on the zonal mean circulation
Nonlinear forcing mechanisms of the migrating terdiurnal solar tide and their impact on the zonal mean circulation
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DOI：
10.5194/angeo-37-943-2019
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发表时间：
2019-10
影响因子：
1.9
通讯作者：
F. Lilienthal;C. Jacobi
中科院分区：
文献类型：
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作者：
F. Lilienthal;C. Jacobi
抽象的。本文利用一个机械论的全球环流模式研究了中层大气中太阳潮的强迫机制。为了量化它们各自的贡献，我们进行了几个模型实验，并通过关闭其余的源来分离每个强迫机制。我们发现，初始激发是由于对流层和平流层对太阳辐射吸收的周日分量。次级源是非线性潮汐相互作用和重力波潮汐相互作用。因此，虽然在我们的模拟中，太阳加热明显占主导地位的terdailyderday强迫，我们发现，非线性潮汐和重力波的相互作用，在某些季节，在某些高度作出贡献。通过稍微增强不同的激发源，我们测试了背景环流对这些动力学变化的敏感性。结果表明，重力波拖曳力的增加会对中高层大气动力学产生强烈的影响，包括重力波拖曳力的异常变化、热层中性风的减弱以及热层温度的显著变化（取决于重力波拖曳力的强弱）。相反，非线性潮汐相互作用对中层大气背景动力学的影响很小。
Abstract. We investigate the forcing mechanisms of the terdiurnal solar tide in the middle atmosphere using a mechanistic global circulation model. In order to quantify their individual contributions, we perform several model experiments and separate each forcing mechanism by switching off the remaining sources. We find that the primary excitation is owing to the terdiurnal component of solar radiation absorption in the troposphere and stratosphere. Secondary sources are nonlinear tide–tide interactions and gravity wave–tide interactions. Thus, although the solar heating clearly dominates the terdiurnal forcing in our simulations, we find that nonlinear tidal and gravity wave interactions contribute in certain seasons and at certain altitudes. By slightly enhancing the different excitation sources, we test the sensitivity of the background circulation to these changes of the dynamics. As a result, the increase of terdiurnal gravity wave drag can strongly affect the middle and upper atmosphere dynamics, including an irregular change of the terdiurnal amplitude, a weakening of neutral winds in the thermosphere, and a significant temperature change in the thermosphere, depending on the strength of the forcing. On the contrary, the influence of nonlinear tidal interactions on the middle atmosphere background dynamics is rather small.