Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation
Observations of surface momentum exchange over the marginal ice zone and recommendations for its parametrisation
复制标题
DOI：
10.5194/acp-16-1545-2016
复制
发表时间：
2016-01-01
影响因子：
6.3
通讯作者：
King, J. C.
中科院分区：
文献类型：
--
作者：
Elvidge, A. D.;Renfrew, I. A.;King, J. C.
全面的飞机观测被用来计算北极边缘冰区（MIZ）的表面粗糙度，并因此对MIZ表面动量交换的参数化提出建议。这些观测是作为北极气溶胶-云耦合和气候相互作用（ACCA-CIA）项目的一部分，从两架飞机上在巴伦支海和弗拉姆海峡收集的。这是目前在北极MIZ上空进行的此类飞机观测总数的两倍。涡度相关方法被用来从湍流风速测量中获得10 m中性阻力系数（C-DN 10）的估计值，并采用一种新的方法，使用涡度和表面温度来获得冰分数。在0.6至0.8范围内的冰分数处发现峰值表面粗糙度（C-DN 10中的平均四分位数范围为1.25至2.85 +/- 10（-3））。C-DN 10作为冰分数的函数被发现通过由领先的参数化方案提供的负偏斜分布很好地近似（Lupkes等人，2012年），专门为海冰阻力在MIZ，其中两个组成部分的阻力皮肤和形式阻力分别量化。目前的参数化方案中使用的天气和气候模式与我们的结果进行了比较，大多数被发现是物理上不合理的和不具代表性的。Lupkes et al.（2012）方案建议采用计算简单的形式，调整参数设置。一个很好的协议持有不同地点的数据子集，尽管海冰条件的差异。在巴伦支海的冰条件，其特点是小，松散的浮冰，被发现与较高的C-DN 10值，特别是在较高的冰分数比那些弗拉姆海峡，在那里通常更大，更平滑的浮冰观察。因此，海冰的形态和浮冰的大小对表面粗糙度的重要影响是公认的，并在此参数化方案的代表性的改进，建议为今后的研究。
Comprehensive aircraft observations are used to characterise surface roughness over the Arctic marginal ice zone (MIZ) and consequently make recommendations for the parametrisation of surface momentum exchange in the MIZ. These observations were gathered in the Barents Sea and Fram Strait from two aircraft as part of the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCA-CIA) project. They represent a doubling of the total number of such aircraft observations currently available over the Arctic MIZ. The eddy covariance method is used to derive estimates of the 10m neutral drag coefficient (C-DN10) from turbulent wind velocity measurements, and a novel method using albedo and surface temperature is employed to derive ice fraction. Peak surface roughness is found at ice fractions in the range 0.6 to 0.8 (with a mean interquartile range in C-DN10 of 1.25 to 2.85 +/- 10(-3) ). C-DN10 as a function of ice fraction is found to be well approximated by the negatively skewed distribution provided by a leading parametrisation scheme (Lupkes et al., 2012) tailored for sea-ice drag over the MIZ in which the two constituent components of drag-skin and form drag-are separately quantified. Current parametrisation schemes used in the weather and climate models are compared with our results and the majority are found to be physically unjustified and unrepresentative. The Lupkes et al. (2012) scheme is recommended in a computationally simple form, with adjusted parameter settings. A good agreement holds for subsets of the data from different locations, despite differences in sea-ice conditions. Ice conditions in the Barents Sea, characterised by small, unconsolidated ice floes, are found to be associated with higher C-DN10 values-especially at the higher ice fractions-than those of Fram Strait, where typically larger, smoother floes are observed. Consequently, the important influence of sea-ice morphology and floe size on surface roughness is recognised, and improvement in the representation of this in parametrisation schemes is suggested for future study.