The MOSAiC sea ice albedo record: its context and role for informing improved surface radiative budgets in a climate model
The MOSAiC sea ice albedo record: its context and role for informing improved surface radiative budgets in a climate model
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MOSAiC 海冰反照率记录：其背景和在气候模型中改善表面辐射预算的作用
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发表时间：
2021
期刊：
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通讯作者：
D. Bailey
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作者：
B. Light;M. Holland;M. Smith;D. Perovich;M. Webster;David Clemens;F. Linhardt;Ian A. Raphael;D. Bailey
<p>海冰融化既是夏季融化演变的驱动力，也是其后果。收集全面的观测结果并开发准确，通用和一致的基于物理学的模型的能力是我们定量了解海冰质量和热量收支以及各种相关反馈过程的核心。在MOSAiC现场活动期间记录的海冰反射波扩展了我们对特定冰类型的光学特性及其季节演变的了解。这一新的数据集补充和扩展了1998年在博福特海进行的北冰洋表面热量收支（SHEBA）活动期间所作的观测。它也提供了一个机会，以改善气候模式中海冰覆盖的短波辐射分割的数值处理。具体而言，观测包括由地面观测者对两类测量进行的光谱和宽带连续测量：1）单个冰类型，包括积雪覆盖的冰（融化之前和融化期间），裸露的融化冰，积水冰和沉积物冰，以及2）在整个季节周期内测量的时间序列。MOSAiC和SHEBA的数据集显示出显着的相似性，相对于稳定的光谱的裸露，融化的夏季冰和季节性演变的代表性测量线。这两个数据集包括协调的物理特性表征，这是气候模拟中辐射传输处理的发展和完善的关键。</p><p>在这项工作中，我们将观测记录与CESM 2模型运行产生的结果进行了比较。共同体地球系统模式（CESM 2）是一个耦合气候模式，其中包括基于物理的海冰辐射传输处理。该模型依赖于一个2流三角洲爱丁顿解决方案与规定的冰型特定的固有光学特性。具体来说，我们认为新的子网格尺度诊断模型中，详细的辐射分区为个人的表面类型和厚度类别。观测值和模拟值之间的比较被认为是个别表面类型，总的CONDO估计，和他们的季节性进展的CONDO。特别是，我们使用这些比较得出一个定量的图片的整体分割短波辐射的冰盖，以及它如何在过去的几十年中发生了变化。这些结果可以帮助确定在哪里可以完成最实质性的模型升级，以及在哪里应该进行最好的观测投资。</p>
<p>Sea ice albedo is both a driver and a consequence of summer melt evolution. The ability to collect comprehensive observations and develop accurate, general, and consistent physics-based models is central to our quantitative understanding of sea ice mass and heat budgets and a variety of associated feedback processes. Sea ice albedos recorded during the MOSAiC field campaign have extended our knowledge of the optical properties of specific ice types as well as their seasonal evolution. This new dataset complements and extends observations made during the Surface Heat Budget of the Arctic Ocean (SHEBA) campaign in the Beaufort Sea in 1998. It also presents an opportunity to improve numerical treatment of shortwave radiation partitioning by sea ice covers in climate models. Specifically, the observations include spectral and broadband albedo measurements made by observers on the surface for two classes of measurement: 1) individual ice types including snow covered ice (prior to and during melt), bare melting ice, ponded ice, and sediment-laden ice, and 2) time series measured over the full seasonal cycles. The MOSAiC and SHEBA data sets show remarkable similarity with respect to the steady spectral albedo of bare, melting summer ice and the seasonal evolution measured over representative survey lines. Both data sets include coordinated physical property characterization, which is key to the development and refinement of radiative transfer treatment in climate modeling.</p><p>In this work, we compare the observational record with results generated from runs of the CESM2 model. The Community Earth System Model (CESM2) is a coupled climate model that includes a physics-based radiative transfer treatment for sea ice. This model relies on a 2-stream delta-Eddington solution with prescribed ice-type-specific inherent optical properties. Specifically, we consider newly available sub-gridscale diagnostics in the model that detail the radiative partitioning for individual surface types and thickness categories. Comparisons between observed and modeled values are considered for the albedo of individual surface types, aggregate albedo estimates, and their seasonal progression. In particular, we use these comparisons to derive a quantitative picture of the overall partitioning of shortwave radiation by the ice cover, and how it has changed over past decades. These results can help pinpoint where the most substantial model upgrades can be accomplished as well as where the best observational investments should be made.</p>