Surface heat and moisture exchange in the marginal ice zone: Observations and a new parameterization scheme for weather and climate models
Surface heat and moisture exchange in the marginal ice zone: Observations and a new parameterization scheme for weather and climate models
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DOI：
10.1029/2021jd034827
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发表时间：
2021-08
影响因子：
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通讯作者：
A. Elvidge;I. Renfrew;I. Brooks;P. Srivastava;M. Yelland;J. Prytherch
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作者：
A. Elvidge;I. Renfrew;I. Brooks;P. Srivastava;M. Yelland;J. Prytherch
从两个北极领域的运动飞机观测被用来解释和模拟表面的热量和水分交换的边缘冰区（MIZ）。我们表明，表面粗糙度长度的热量和水分在未破碎的海冰随粗糙雷诺数（R;本身的功能的动量，z 0，和表面风应力的粗糙度长度），在空气动力学平滑（R 2.5）制度之间的过渡峰值。Andreas（1987）的概念模型准确地再现了这一峰值，与目前两个最先进的数值天气预报模式中使用的简单参数化不同，这两个模式对R ε不敏感。我们提出了一个新的，简单的参数化表面交换的MIZ，融合了Andreas（1987）的概念模型，海冰与表面交换的水作为海冰浓度的函数。在离线测试中，该混合A87方案在“IGP”现场活动期间观察到的粗糙条件下比现有方案表现得好得多。混合A87方案的总湍流热通量偏差从英国气象局统一模式和欧洲中期天气预报中心综合预报系统方案的48和80 W m-2分别降低到13 W m-2。在“ACCACIA”现场活动期间观察到的相对平稳的条件下，它的表现也略好。然而，这个新方案的好处是依赖于通过z 0的海冰地形的表示，在海冰表面交换参数化的不确定性的一个关键的剩余来源。
Aircraft observations from two Arctic field campaigns are used to characterise and model surface heat and moisture exchange over the marginal ice zone (MIZ). We show that the surface roughness lengths for heat and moisture over unbroken sea ice vary with roughness Reynolds number (R✶; itself a function of the roughness length for momentum, z0, and surface wind stress), with a peak at the transition between aerodynamically smooth (R✶ 2.5) regimes. The conceptual model of Andreas (1987) accurately reproduces this peak, in contrast to the simple parameterizations currently employed in two state-of-the-art numerical weather prediction models, which are insensitive to R✶. We propose a new, simple parameterization for surface exchange over the MIZ that blends the Andreas (1987) conceptual model for sea ice with surface exchange over water as a function of sea ice concentration. In offline tests, this Blended A87 scheme performs much better than the existing schemes for the rough conditions observed during the ‘IGP’ field campaign. The bias in total turbulent heat flux across the MIZ is reduced to only 13 W m-2 for the Blended A87 scheme, from 48 and 80 W m-2 for the Met Office Unified Model and ECMWF Integrated Forecast System schemes, respectively. It also performs marginally better for the comparatively smooth conditions observed during the ‘ACCACIA’ field campaign. However, the benefit of this new scheme is dependent on the representation of sea ice topography via z0; a key remaining source of uncertainty in surface exchange parameterization over sea ice.