The interaction between gravity waves and solar tides: Results from 4‐D ray tracing coupled to a linear tidal model
The interaction between gravity waves and solar tides: Results from 4‐D ray tracing coupled to a linear tidal model
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DOI：
10.1002/2015ja021349
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发表时间：
2015-08
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影响因子：
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通讯作者：
B. Ribstein;U. Achatz;F. Senf
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文献类型：
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作者：
B. Ribstein;U. Achatz;F. Senf
通过三维射线追踪器模型和线性潮汐模型的耦合研究了太阳潮汐（ST）和重力波（GW）之间的相互作用。射线追踪器模型描述了由月平均气候和 ST 形成的空间和时间相关背景上的引力波动态。它没有受到传统引力波参数化的典型简化的影响，其中忽略了水平引力波传播和水平背景梯度对引力波动态的影响。射线追踪器模型使用 Wentzel-Kramers-Brillouin (WKB) 理论的变体，其中位置波数空间中的光谱描述有助于避免数值不稳定，否则可能会在类似苛性碱的情况下发生。潮汐模型是通过对月平均值的原始方程进行线性化获得的，考虑到静止的行星波。射线追踪器模型和潮汐模型之间的通信是通过使用与纬度和高度相关的系数（称为瑞利摩擦和牛顿松弛）来促进的，并且是从相对于 ST 及其趋势的引力波动量和浮力通量的回归获得的。这些系数由射线追踪器模型计算，然后应用到潮汐模型中。迭代过程连续更新重力场和潮汐场，直到达到收敛。尽管所采用的引力波源很简单，但观测到的潮汐动力学的许多方面都被再现了。结果表明，传统的“单列”近似会导致显着高估引力波通量，从而低估 ST 振幅，这表明总体上引力波参数化是一个敏感问题。
The interaction between solar tides (STs) and gravity waves (GWs) is studied via the coupling of a three‐dimensional ray tracer model and a linear tidal model. The ray tracer model describes GW dynamics on a spatially and time‐dependent background formed by a monthly mean climatology and STs. It does not suffer from typical simplifications of conventional GW parameterizations where horizontal GW propagation and the effects of horizontal background gradients on GW dynamics are neglected. The ray tracer model uses a variant of Wentzel‐Kramers‐Brillouin (WKB) theory where a spectral description in position wave number space is helping to avoid numerical instabilities otherwise likely to occur in caustic‐like situations. The tidal model has been obtained by linearization of the primitive equations about a monthly mean, allowing for stationary planetary waves. The communication between ray tracer model and tidal model is facilitated using latitude‐ and altitude‐dependent coefficients, named Rayleigh friction and Newtonian relaxation, and obtained from regressing GW momentum and buoyancy fluxes against the STs and their tendencies. These coefficients are calculated by the ray tracer model and then implemented into the tidal model. An iterative procedure updates successively the GW fields and the tidal fields until convergence is reached. Notwithstanding the simplicity of the employed GW source, many aspects of observed tidal dynamics are reproduced. It is shown that the conventional “single‐column” approximation leads to significantly overestimated GW fluxes and hence underestimated ST amplitudes, pointing at a sensitive issue of GW parameterizations in general.