SNICAR-ADv3: a community tool for modeling spectral snow albedo
SNICAR-ADv3: a community tool for modeling spectral snow albedo
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DOI：
10.5194/gmd-14-7673-2021
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发表时间：
2021-12-21
影响因子：
5.1
通讯作者：
Zender, Charles S.
中科院分区：
文献类型：
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作者：
Flanner, Mark G.;Arnheim, Julian B.;Zender, Charles S.
在过去的15年里，雪、冰和气溶胶辐射(SNICAR)模型在不同的能力下被用来模拟具有光吸收成分(LACS)的雪的光谱反照率。最近的研究已将该模型扩展到包括添加-加倍两流解算器和非球形冰粒、二氧化碳雪、雪藻以及新型矿物粉尘、火山灰和棕色碳的表示。还存在用于计算宽带反照率的冰折射率和依赖于太阳天顶角的表面光谱辐照度的新选择。该模型的光谱范围还扩展到更深的紫外线，用于研究地外和高海拔冰冻层表面。然而，到目前为止，这些改进和功能还没有合并到统一的代码库中。在这里，我们记录了公开可用的SNICAR-ADv3源代码、基于网络的模型和随附的组成光学属性库的制定和评估。非球形冰粒向正向散布的强度较小，它的使用将LACS模拟的反照率扰动减少了9%-31%，这取决于应用了三种可用的非球形形状中的哪一种。该模型与七项研究对雪反照率的测量结果进行了很好的比较，尽管影响雪反照率的关键特性并未完全受到测量的限制，包括积雪顶部亚毫米级的冰有效颗粒尺寸、LACS相对于冰颗粒的混合状态以及特定地点的LAC光学特性。新的默认冰折射率在光谱的蓝色和紫外线部分产生极高的纯雪反照率(>；0.99)，到目前为止，这样的值只在南极洲测量到。还需要做更多的工作，特别是在雪藻的表现方面，包括对不同的色素表达和藻细胞浓度如何影响雪的反照率进行实验验证。液态水对光谱雪反照率的影响的表述和测量也是必要的。
The Snow, Ice, and Aerosol Radiative (SNICAR) model has been used in various capacities over the last 15 years to model the spectral albedo of snow with light-absorbing constituents (LACs). Recent studies have extended the model to include an adding-doubling two-stream solver and representations of non-spherical ice particles; carbon dioxide snow; snow algae; and new types of mineral dust, volcanic ash, and brown carbon. New options also exist for ice refractive indices and solar-zenith-angle-dependent surface spectral irradiances used to derive broadband albedo. The model spectral range was also extended deeper into the ultraviolet for studies of extraterrestrial and high-altitude cryospheric surfaces. Until now, however, these improvements and capabilities have not been merged into a unified code base. Here, we document the formulation and evaluation of the publicly available SNICAR-ADv3 source code, web-based model, and accompanying library of constituent optical properties. The use of non-spherical ice grains, which scatter less strongly into the forward direction, reduces the simulated albedo perturbations from LACs by similar to 9%-31%, depending on which of the three available non-spherical shapes are applied. The model compares very well against measurements of snow albedo from seven studies, though key properties affecting snow albedo are not fully constrained with measurements, including ice effective grain size of the top sub-millimeter of the snowpack, mixing state of LACs with respect to ice grains, and site-specific LAC optical properties. The new default ice refractive indices produce extremely high pure snow albedo (>0.99) in the blue and ultraviolet part of the spectrum, with such values only measured in Antarctica so far. More work is needed particularly in the representation of snow algae, including experimental verification of how different pigment expressions and algal cell concentrations affect snow albedo. Representations and measurements of the influence of liquid water on spectral snow albedo are also needed.