A parameterization of the ice‐ocean drag coefficient
A parameterization of the ice‐ocean drag coefficient
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DOI：
10.1029/2010jc006878
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发表时间：
2011-07
影响因子：
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通讯作者：
P. Lu;Zhijun Li;B. Cheng;M. Leppäranta
中科院分区：
文献类型：
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作者：
P. Lu;Zhijun Li;B. Cheng;M. Leppäranta
[1]通过将海洋拖曳力分解为浮冰边缘形状拖曳力、脊龙骨形状拖曳力和冰底表面摩擦力三个分量，建立了冰-海洋拖曳系数（Cw）的参数化模型。通过这些量，Cw被表示为可观测海冰几何参数的函数。进行了敏感性研究，以调查不同的海冰条件对Cw的影响。结果表明，随着冰浓度（A）的增加，Cw先增大后减小，这与气-冰阻力系数的观测结果相似，主要是由于浮冰边缘形状阻力随冰浓度的非单调变化所致。此外，浮冰边缘的形状阻力总是占主导地位的组成部分，在具有大长宽比（吃水/长度≥ 1/100）的海冰中所占的比例超过60%，这表明在海冰动力学模型中，特别是对于边缘冰区（MIZ），包括该项的必要性。当起垄强度极高（深度/间距≥ 1/20）时，脊龙骨上的形状阻力才占主导地位。此外，大的Cw值不能仅仅由包含形状阻力项引起，也不能由粗糙冰底上的大表面摩擦引起。最后，对于中等脊强度的MIZ的典型情况，参数化将低估Cw约30%的粗糙的冰底和超过80%的光滑的冰底，如果没有考虑形状阻力。
[1] A parameterization of the ice-ocean drag coefficient (Cw) was developed through partitioning the oceanic drag force into three components: (1) form drag on the floe edge, (2) form drag on the ridge keel, and (3) skin friction on the ice bottom. Through these quantities, Cw was expressed as a function of observable sea ice geometric parameters. Sensitivity studies were carried out to investigate the influence of varying sea ice conditions on Cw. The results revealed that Cw increases first and then decreases with increasing ice concentration (A), similar to the observations of the air-ice drag coefficient, and which is mainly attributed to the nonmonotonic variation of the form drag on the floe edge with ice concentration. Moreover, the form drag on the floe edge is always the dominant component, having a proportion of more than 60% in sea ice with a large aspect ratio (draft/length ≥ 1/100), indicating the necessity of including this term in sea ice dynamic models, particularly for the marginal ice zone (MIZ). The form drag on the ridge keel becomes dominant only when the ridging intensity is extremely high (depth/spacing ≥ 1/20). Additionally, a large value of Cw cannot be caused only by the inclusion of form drag terms but also by large skin friction over rough ice bottoms. Finally, for typical situations in the MIZ with moderate ridging intensity, the parameterization will underestimate Cw by approximately 30% for a rough ice bottom and by over 80% for a smooth ice bottom if no form drags are considered.