A parametrization, based on sea ice morphology, of the neutral atmospheric drag coefficients for weather prediction and climate models
A parametrization, based on sea ice morphology, of the neutral atmospheric drag coefficients for weather prediction and climate models
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DOI：
10.1029/2012jd017630
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发表时间：
2012-07
影响因子：
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通讯作者：
C. Lüpkes;V. Gryanik;J. Hartmann;E. L. Andreas
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文献类型：
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作者：
C. Lüpkes;V. Gryanik;J. Hartmann;E. L. Andreas
[1]基于将总表面阻力分为表层阻力和形态阻力的划分概念，推导出了具有不同形态的极地海冰上中性10米阻力系数的参数化层次。新的推导提供了阻力系数作为海冰浓度和粗糙度元素特征长度尺度的函数，比以前的类似方法需要更少的假设。结果表明，形式阻力变异性可以解释边缘海冰区和夏季内北极地区表面阻力的变异性。在MIZ中，形状阻力是由浮冰边缘产生的；在北极内部，它是由融化池的边缘和由于冰表面相对于开放水面的高度而产生的。结果表明，在新概念中，当对浮冰和熔池几何形状进行特定的简化时，观测到的中性阻力系数较早地拟合是一种特殊情况。由于MIZ和夏季北极不同的地表形态，导致阻力系数对海冰浓度的函数依赖性不同。在平均条件下，这些差异只导致MIZ和夏季阻力系数之间的微小差异，但它们可能对局部大气动量输送到海冰很重要。新的参数化公式可用于当前条件，也可用于海冰条件变化的未来气候情景。
[1] A hierarchy of parametrizations of the neutral 10 m drag coefficients over polar sea ice with different morphology regimes is derived on the basis of a partitioning concept that splits the total surface drag into contributions of skin drag and form drag. The new derivation, which provides drag coefficients as a function of sea ice concentration and characteristic length scales of roughness elements, needs fewer assumptions than previous similar approaches. It is shown that form drag variability can explain the variability of surface drag in the marginal sea ice zone (MIZ) and in the summertime inner Arctic regions. In the MIZ, form drag is generated by floe edges; in the inner Arctic, it is generated by edges at melt ponds and leads due to the elevation of the ice surface relative to the open water surface. It is shown that an earlier fit of observed neutral drag coefficients is obtained as a special case within the new concept when specific simplifications are made which concern the floe and melt pond geometry. Due to the different surface morphologies in the MIZ and summertime Arctic, different functional dependencies of the drag coefficients on the sea ice concentration result. These differences cause only minor differences between the MIZ and summertime drag coefficients in average conditions, but they might be locally important for atmospheric momentum transport to sea ice. The new parametrization formulae can be used for present conditions but also for future climate scenarios with changing sea ice conditions.