Inference of optical properties from radiation profiles within melting landfast sea ice
Inference of optical properties from radiation profiles within melting landfast sea ice
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DOI：
10.1029/2007jc004656
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发表时间：
2008-09
影响因子：
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通讯作者：
J. Ehn;T. Papakyriakou;D. Barber
中科院分区：
文献类型：
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作者：
J. Ehn;T. Papakyriakou;D. Barber
[1]2005年4月25日，在哈德逊湾西部融化的1.5至1.7米厚的固定在陆地上的海冰内测量了垂直冰内光谱辐射剖面。由于表面冰受到广泛的融化和重新冻结，海冰分为两种主要类型，即，反射率较高的白色冰和反射率较低的蓝色冰的区域。对于白色冰，短波的短波辐射度约为0.69，对于裸蓝冰，短波辐射度约为0.47。相应的短波透过冰盖的透射率分别约为0.02和0.09。海冰的固有光学特性推断通过捆绑的输入和输出的辐射传输模拟的辐射剖面和冰的物理特性，以及上面和下面的冰盖的辐照度测量。为了同时解释观测到的光谱反射率和透射率，根据以下观测结果将内部冰上方的冰/雪分为三层：雪（白色冰）或含烟灰的薄层（蓝色冰），水线上方的排水冰和水线下方的饱和冰。同样，根据海水界面附近的活冰藻层和底部上方30厘米处主要含有碎屑物质的层的存在，对底部进行了划分。冰的内部，即，由于辐射场几乎是渐近的，而且吸收光谱几乎没有显示出杂质的迹象，因此，距离边界大约20-40厘米的一层纯海冰很好地代表了这一点。散射系数的代表值范围为600-800 m−1，Henyey-Greenstein不对称参数为0.995。对白色冰的观测表明，内部融化的能量中约有40%是由短波辐射直接提供的，而其余的是由于热传导。
[1] Vertical in-ice spectral radiation profiles were measured within melting 1.5- to 1.7-m-thick landfast sea ice in western Hudson Bay on 25 April 2005. Because the surface ice was subject to extensive melting and refreezing, the sea ice had fractioned into two main types, i.e., areas of more reflective white ice and less reflective blue ice. The shortwave albedo was about 0.69 for white ice and 0.47 for bare blue ice. The corresponding shortwave transmittance through the ice cover was about 0.02 and 0.09, respectively. The inherent optical properties of the sea ice were inferred by tying the input and output of radiative transfer simulations to the radiation profiles and the ice physical properties, as well as to the irradiance measurements above and below the ice cover. To explain observed spectral albedo and transmittance simultaneously, the ice/snow above the interior ice was divided into three layers on the basis of the following observations: snow (white ice) or a thin soot containing layer (blue ice), drained ice above and saturated ice below the waterline. Similarly, the bottom portion was divided on the basis of the presence of a living ice algae layer adjacent to the seawater interface and a layer extending 30 cm above the bottom containing mostly detrital matter. The interior of the ice, i.e., roughly 20–40 cm from boundaries, was well-represented by a single layer of pure sea ice as the radiation field was nearly asymptotic and the absorption spectra showed little evidence of impurities. Representative values for the scattering coefficient ranged 600–800 m−1, with a Henyey-Greenstein asymmetry parameter of 0.995. Observations within white ice suggest that about 40% of the energy responsible of the internal melting was provided directly by shortwave radiation, while the rest is due to heat conduction.