Eddy viscosity and diffusivity in the modon-sea model
Eddy viscosity and diffusivity in the modon-sea model
复制标题
modon-sea 模型中的涡粘性和扩散率
DOI：
10.1357/002224011799849426
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发表时间：
2011
影响因子：
0.5
通讯作者：
T. Radko
中科院分区：
文献类型：
--
作者：
T. Radko
建立了一个确定性模型来评价和解释海洋涡旋流的动量耗散率。该理论基于中尺度变率的经典概念化——Stern的模态-海解——它代表了正压β平面上稳定紧凑的偶极涡旋的紧密排列。在我们的模型中，周期模态-海模式受到大尺度扰动，弱调制单个模态的振幅。渐近多尺度分析可以明确地描述近海涡旋与扰动流之间的相互作用。这种相互作用导致大尺度扰动的系统性减弱。模型中的涡动黏度对显耗散的依赖性较弱，但随模态分离的增加而迅速减小。基于modon-sea模式的估计值与通常用于粗分辨率数值海洋模式的粘度值相当，但小于。用解析法和数值法相结合的方法对被动示踪剂的涡流扩散系数进行了评价和讨论。通过直接数值模拟成功地验证了渐近理论。
A deterministic model is developed to evaluate and explain the rate of dissipation of momentum in eddying oceanic flows. Theory is based on a classical conceptualization of mesoscale variability – Stern’s modon-sea solution – which represents a closely packed array of steady compact dipolar vortices on the barotropic beta-plane. In our model, the periodic modon-sea pattern is subjected to a large-scale perturbation, weakly modulating the amplitude of the individual modons. The asymptotic multiscale analysis makes it possible to explicitly describe the interaction between the modon-sea eddies and the perturbing flow. This interaction results in a systematic weakening of the large-scale perturbation. The eddy viscosity in the model is found to be only weakly dependent on the explicit dissipation but rapidly decreases with increased separation of the modons. The estimates based on the modon-sea model are comparable to, but less than, the values of viscosity typically used in coarse resolution numerical ocean models. The eddy diffusivity of passive tracers is also evaluated and discussed in terms of a combination of analytical and numerical methods. The asymptotic theories are successfully tested by direct numerical simulations.