Impact of Grain Shape and Multiple Black Carbon Internal Mixing on Snow Albedo: Parameterization and Radiative Effect Analysis
Impact of Grain Shape and Multiple Black Carbon Internal Mixing on Snow Albedo: Parameterization and Radiative Effect Analysis
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DOI：
10.1002/2017jd027752
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发表时间：
2018-01
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影响因子：
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通讯作者：
C. He;K. Liou;Y. Takano;P. Yang;L. Qi;Fei Chen
中科院分区：
文献类型：
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作者：
C. He;K. Liou;Y. Takano;P. Yang;L. Qi;Fei Chen
我们通过明确解析形状和混合结构来量化颗粒形状和多个黑碳（BC）-雪内部混合对雪的影响。非球形雪粒往往比具有相同有效尺寸的球形雪粒具有更高的折射率，而由于形状效应导致的折射率差异随着颗粒尺寸的增加而增加，在可见光和近红外波段，有效半径为1，000 μm时分别高达0.013和0.055。BC-雪的内部混合减少了波长< ~1.5 μm的雪的散射，在较长波长下的影响可以忽略不计。在紫外和可见波段，非球形雪粒显示出比具有相同有效尺寸的球体更少的BC诱导的Crackdo减少，减少高达0.06。与外部混合相比，内部混合增强了雪的反射率降低了1.2-2.0倍，在可见光波长取决于BC浓度和雪的形状。由于雪粒的非球形和BC-雪的内部混合点，对雪道减少的相反影响，需要在气候模拟中同时仔细研究这两个因素。我们进一步开发参数化雪的颗粒形状和BC-雪内部/外部混合，并减少其减少。将参数化与中国、北美和北极的雪中硼浓度测量结果相结合，我们估计，与球形颗粒相比，非球形雪粒将硼浓度引起的辐射效应降低了50%。此外，BC-雪内部混合提高了高达30%（130%）的球形（非球形）颗粒相对于外部混合的反相效果。雪的形状和BC-雪混合状态引起的总体不确定性约为21- 32%。
We quantify the effects of grain shape and multiple black carbon (BC)‐snow internal mixing on snow albedo by explicitly resolving shape and mixing structures. Nonspherical snow grains tend to have higher albedos than spheres with the same effective sizes, while the albedo difference due to shape effects increases with grain size, with up to 0.013 and 0.055 for effective radii of 1,000 μm at visible and near‐infrared bands, respectively. BC‐snow internal mixing reduces snow albedo at wavelengths < ~1.5 μm, with negligible effects at longer wavelengths. Nonspherical snow grains show less BC‐induced albedo reductions than spheres with the same effective sizes by up to 0.06 at ultraviolet and visible bands. Compared with external mixing, internal mixing enhances snow albedo reduction by a factor of 1.2–2.0 at visible wavelengths depending on BC concentration and snow shape. The opposite effects on albedo reductions due to snow grain nonsphericity and BC‐snow internal mixing point toward a careful investigation of these two factors simultaneously in climate modeling. We further develop parameterizations for snow albedo and its reduction by accounting for grain shape and BC‐snow internal/external mixing. Combining the parameterizations with BC‐in‐snow measurements in China, North America, and the Arctic, we estimate that nonspherical snow grains reduce BC‐induced albedo radiative effects by up to 50% compared with spherical grains. Moreover, BC‐snow internal mixing enhances the albedo effects by up to 30% (130%) for spherical (nonspherical) grains relative to external mixing. The overall uncertainty induced by snow shape and BC‐snow mixing state is about 21–32%.