Effects of Snow Grain Shape and Mixing State of Snow Impurity on Retrieval of Snow Physical Parameters From Ground‐Based Optical Instrument
Effects of Snow Grain Shape and Mixing State of Snow Impurity on Retrieval of Snow Physical Parameters From Ground‐Based Optical Instrument
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DOI：
10.1029/2019jd031858
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发表时间：
2020-08
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影响因子：
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通讯作者：
T. Tanikawa;K. Kuchiki;T. Aoki;Hiroshi Ishimoto;Akihiro Hachikubo;M. Niwano;Masahiro Hosaka;S. Matoba;Yuji Kodama;Yukiyoshi Iwata;Knut Stamnes
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文献类型：
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作者：
T. Tanikawa;K. Kuchiki;T. Aoki;Hiroshi Ishimoto;Akihiro Hachikubo;M. Niwano;Masahiro Hosaka;S. Matoba;Yuji Kodama;Yukiyoshi Iwata;Knut Stamnes
为了从光学遥感数据中准确反演雪中的雪颗粒大小和光吸收颗粒浓度，提出了新的雪颗粒模型和雪杂质混合模型。两种冰晶模型，不规则形状的Voronoi柱，和Voronoi聚集。雪可以通过两个过程捕获雨水：干沉积和湿沉积。提出了两种不同的雪杂质混合模型。一个是外部混合模型。我们采用了一个涂层球模型，其中煤烟是亲水性颗粒来代表气溶胶的吸湿性，并假设亲水性煤烟颗粒与雪颗粒外部混合。另一种是内部混合模型。采用动态有效介质近似方法，将煤烟颗粒随机分布在任意粒径分布和数量浓度的雪颗粒中。这些模型的验证是使用地面光谱辐射计系统与现场测量数据进行的。对于雪粒度反演，Voronoi混合模型无缝地表示各种雪类型的几何形状和光学特性，可以提供准确的反演。对于雪中重金属浓度的反演，根据季节和观测点的不同，采用不同的混合状态模型，可以得到较准确的结果。还讨论了影响反演精度的地面坡度反演雪参数的不确定性。这些模型有望通过大气-雪系统中的辐射传输建模，用于先进的机载/卫星遥感和气候研究。
We proposed new snow grain model and snow impurity mixture models for the purpose of accurate retrievals of snow grain size and concentration of light‐absorbing particles (LAP) in snow from the optical remote sensing data. Two kinds of ice crystal models, irregularly shaped Voronoi columns, and Voronoi aggregates were employed. LAP can be captured by the snow through two processes: dry and wet deposition. Two different snow impurity mixture models were proposed. One is an external mixture model. We employed a coated sphere model in which soot were hydrophilic particles to represent a hygroscopic property of aerosol and assumed the hydrophilic soot particles to be externally mixed with snow particles. The other is an internal mixture model. We employed a dynamic effective medium approximation method in which soot particles were randomly located within snow particle with any size distribution and number concentration. Validation of these models is conducted using a ground‐based spectral radiometer system with in situ measurement data. For snow grain size retrievals, a Voronoi mixture model seamlessly representing a geometrical shape and an optical properties of various snow types can provide accurate retrievals. For the retrieval of LAP concentration in snow, employing different mixing state models depending on season and measurement site gives accurate results. We also discussed the uncertainty of retrieved snow parameters on the surface slope involved in the retrieval accuracy. These models are expected to be useful for advanced airborne/satellite remote sensing and climate studies via radiative transfer modeling in the atmosphere‐snow system.