Enhanced Snow Absorption and Albedo Reduction by Dust‐Snow Internal Mixing: Modeling and Parameterization
Enhanced Snow Absorption and Albedo Reduction by Dust‐Snow Internal Mixing: Modeling and Parameterization
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DOI：
10.1029/2019ms001737
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发表时间：
2019-11
影响因子：
6.8
通讯作者：
C. He;K. Liou;Y. Takano;Fei Chen;M. Barlage
中科院分区：
文献类型：
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作者：
C. He;K. Liou;Y. Takano;Fei Chen;M. Barlage
我们扩展了一个随机气溶胶-雪气溶胶模型，以明确地模拟灰尘内部/外部混合不同形状的雪粒，并首次量化了灰尘-雪内部混合和雪的非球形对雪的光学特性和气溶胶的综合影响。沙尘-雪内部/外部混合显著增强了雪在<1.0 μm波长处的单次散射和吸收，内部混合（相对于外部混合）和更高的粉尘浓度具有更强的增强作用，但对雪的大小和形状变化的依赖性非常弱。与纯雪相比，尘雪内部混合在<1.0 μm的波长下大大减少了雪的散射，更高的粉尘浓度，更大的雪尺寸和球形（相对于非球形）雪形状的减少更大。与内部混合相比，尘-雪外部混合通常显示出相似的光谱模式，即雪的大小和形状的影响。然而，相对于外部混合，尘-雪内部混合在可见光（近红外）波段将可吸收性降低的幅度提高了10%-30%（10%-230%）。当雪粒变得更大或非球形时，这种相对增强会更强，雪的大小和形状也会产生类似的影响。此外，对于尘雪外部和内部混合，非球形雪粒比球形雪粒具有高达~45%的弱散射减少，这取决于雪的大小，灰尘浓度和波长。尘雪混合状态和雪的形状的交互作用突出了在雪建模中同时考虑这两个因素的重要性。对于土地/气候模式的应用，我们开发的参数化粉尘对雪的光学特性和高精度的反射。
We extend a stochastic aerosol‐snow albedo model to explicitly simulate dust internally/externally mixed with snow grains of different shapes and for the first time quantify the combined effects of dust‐snow internal mixing and snow nonsphericity on snow optical properties and albedo. Dust‐snow internal/external mixing significantly enhances snow single‐scattering coalbedo and absorption at wavelengths of <1.0 μm, with stronger enhancements for internal mixing (relative to external mixing) and higher dust concentrations but very weak dependence on snow size and shape variabilities. Compared with pure snow, dust‐snow internal mixing reduces snow albedo substantially at wavelengths of <1.0 μm, with stronger reductions for higher dust concentrations, larger snow sizes, and spherical (relative to nonspherical) snow shapes. Compared to internal mixing, dust‐snow external mixing generally shows similar spectral patterns of albedo reductions and effects of snow size and shape. However, relative to external mixing, dust‐snow internal mixing enhances the magnitude of albedo reductions by 10%–30% (10%–230%) at the visible (near‐infrared) band. This relative enhancement is stronger as snow grains become larger or nonspherical, with comparable influences from snow size and shape. Moreover, for dust‐snow external and internal mixing, nonspherical snow grains have up to ~45% weaker albedo reductions than spherical grains, depending on snow size, dust concentration, and wavelength. The interactive effect of dust‐snow mixing state and snow shape highlights the importance of accounting for these two factors concurrently in snow modeling. For application to land/climate models, we develop parameterizations for dust effects on snow optical properties and albedo with high accuracy.