On the interplay between horizontal resolution and wave drag and their effect on tidal baroclinic mode waves in realistic global ocean simulations
On the interplay between horizontal resolution and wave drag and their effect on tidal baroclinic mode waves in realistic global ocean simulations
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DOI：
10.1016/j.ocemod.2020.101656
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发表时间：
2020-08-01
期刊：
影响因子：
3.2
通讯作者：
Zhao, Zhongxiang
中科院分区：
文献类型：
--
作者：
Buijsman, Maarten C.;Stephenson, Gordon R.;Zhao, Zhongxiang
利用两个实际强迫的全球混合坐标海洋模式（HYCOM），研究了水平分辨率和波阻阻尼对M-2半日潮能量的影响。该模式共41层，水平分辨率分别为8 km（1/12.5度; H12）和4 km（1/25度; H25）。在这两种模拟中，通过调整线性波阻力的强度来最小化表面潮汐误差，线性波阻力是表面潮汐能量转换为未解决的斜压波模式的参数化。在这两个模拟的M-2表面潮汐误差与TPXO 8-图集，测高约束模型，是2.6厘米。与H12相比，H25中的表面潮汐能量转换到分解的垂直模式增加了50%。这与从表面潮汐到波阻的能量调谐损失的等效减少相一致。对于这里研究的配置，水平而不是垂直分辨率是限制全球大部分海洋中解析的垂直模式数量的因素：H12中的模式1-2和H25中的模式1-5。波阻也抑制了分解的内潮。波阻强度降低40%不会导致H25中模式1能量密度成比例增加。在更高分辨率的模拟中，地形模式散射和波-波相互作用得到了更好的解决。这允许从模式1到更高模式的能量通量，减轻了对内部潮汐阻尼项的需要。HYCOM模拟验证与分析转换模型和高度推断的海面高度，通量和表面潮汐耗散。H25与这些数据集的一致性最好，接近10%。为了便于从不同持续时间的时间序列中提取的平稳潮汐信号的比较，我们成功地应用了空间变化的校正因子。
The effects of horizontal resolution and wave drag damping on the semidiurnal M-2 tidal energetics are studied for two realistically-forced global HYbrid Coordinate Ocean Model (HYCOM) simulations with 41 layers and horizontal resolutions of 8 km (1/12.5 degrees; H12) and 4 km (1/25 degrees; H25). In both simulations, the surface tidal error is minimized by tuning the strength of the linear wave drag, which is a parameterization of the surface-tide energy conversion to the unresolved baroclinic wave modes. In both simulations the M-2 surface tide error with TPXO8-atlas, an altimetry constrained model, is 2.6 cm. Compared to H12, the surface tide energy conversion to the resolved vertical modes is increased by 50% in H25. This coincides with an equivalent reduction in the tuned loss of energy from the surface tide to the wave drag. For the configurations studied here, the horizontal and not the vertical resolution is the factor limiting the number of vertical modes that are resolved in most of the global ocean: modes 1-2 in H12 and modes 1-5 in H25. The wave drag also dampens the resolved internal tides. The 40% reduction in wave-drag strength does not result in a proportional increase in the mode-1 energy density in H25. In the higher-resolution simulations, topographic mode-scattering and wave-wave interactions are better resolved. This allows for an energy flux out of mode 1 to the higher modes, mitigating the need for an internal tide damping term. The HYCOM simulations are validated with analytical conversion models and altimetry-inferred sea-surface height, fluxes, and surface tide dissipation. H25 agrees best with these data sets to within similar to 10%. To facilitate the comparison of stationary tide signals extracted from time series with different durations, we successfully apply a spatially-varying correction factor.