Impact of topographic internal lee wave drag on an eddying global ocean model
Impact of topographic internal lee wave drag on an eddying global ocean model
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DOI：
10.1016/j.ocemod.2015.10.013
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发表时间：
2016
期刊：
影响因子：
3.2
通讯作者：
D. Trossman;B. Arbic;J. Richman;S. Garner;S. Jayne;A. Wallcraft
中科院分区：
文献类型：
--
作者：
D. Trossman;B. Arbic;J. Richman;S. Garner;S. Jayne;A. Wallcraft
地形内部背风波阻力（以下简称波阻力）的影响，在几个方面的低频率环流的高分辨率全球海洋模式迫使风和气-海浮力通量在这里检查。混合坐标海洋模式（HYCOM）以两种不同的水平分辨率运行（一种名义上为1/12°，另一种为1/25°）。波阻，参数化地形阻塞和产生的背风波所产生的地转流撞击粗糙的地形，被插入到模拟，因为它们运行。这里使用的参数化影响动量方程，从而涡动动能的结构。虽然参数化并不直接改变密度，但背风波对海洋中的贯向混合也有影响。由于波浪阻力和二次底边界层阻力引起的近底总能量耗散几乎增加了一倍，并且由于二次底阻力引起的能量耗散减少了约2倍，与仅具有二次底阻力的模拟相比，在具有插入波浪阻力的模拟中。随着波阻的插入，动能在深渊和三维整体积分中减少。偏折部分地形阻塞被推断为近底动能可以增加的地方，有很少的变化，由二次底阻力耗散的原因之一。尽管在深渊中看到了很大的变化，但在模拟中插入波阻后，在海面附近发生的变化相对较小。在这些诊断中，海表面高度方差和地转表面动能在全球平均上都减少了两倍以上的季节变化。由插入波阻引起的增强喷流位置的改变与喷流位置的时间变化是不可区分的。各种统计测量表明，仅在距海底固定距离内施加波阻，相对于观测结果而言，不会对模型性能造成损害。然而，引入一种新的诊断表明，一种方法来改善波阻参数化是允许背风波动量通量的垂直沉积空间异质性。
The impact of topographic internal lee wave drag (wave drag hereafter) on several aspects of the low-frequency circulation in a high-resolution global ocean model forced by winds and air-sea buoyancy fluxes is examined here. The HYbrid Coordinate Ocean Model (HYCOM) is run at two different horizontal resolutions (one nominally 1/12° and the other 1/25°). Wave drag, which parameterizes both topographic blocking and the generation of lee waves arising from geostrophic flow impinging upon rough topography, is inserted into the simulations as they run. The parameterization used here affects the momentum equations and hence the structure of eddy kinetic energy. Lee waves also have implications for diapycnal mixing in the ocean, though the parameterization does not directly modify the density. Total near-bottom energy dissipation due to wave drag and quadratic bottom boundary layer drag is nearly doubled, and the energy dissipation due to quadratic bottom drag is reduced by about a factor of two, in simulations with an inserted wave drag compared to simulations having only quadratic bottom drag. With the insertion of wave drag, the kinetic energy is reduced in the abyss and in a three-dimensional global integral. Deflection by partial topographic blocking is inferred to be one reason why the near-bottom kinetic energy can increase in locations where there is little change in dissipation by quadratic bottom drag. Despite large changes seen in the abyss, the changes that occur near the sea surface are relatively small upon insertion of wave drag into the simulations. Both the sea surface height variance and geostrophic surface kinetic energy are reduced on global average by more than twice the seasonal variability in these diagnostics. Alterations in the intensified jet positions brought about by inserting wave drag are not distinguishable from the temporal variability of jet positions. Various statistical measures suggest that applying wave drag only within a fixed distance from the seafloor is not detrimental to the model performance relative to observations. However, the introduction of a novel diagnostic suggests that one way to improve the wave drag parameterization is to allow the vertical deposition of lee wave momentum flux to be spatially heterogeneous.