On the surface roughness characteristics of the land fast sea-ice in the Bohai Sea
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摘要: 海冰表面粗糙特征(如高度和坡度)对于海冰表面的电磁散射、辐射和海冰拖拽系数等参数具有重要应用价值,同时也是利用遥感技术准确地区分海冰类型,反演海冰厚度,海冰表面温度和拖拽系数的基础。本文借助于Trimble GX微地形激光扫描仪于2011-2012冬季对盛冰期渤海东岸的5个样点进行了测量,得到了点云图。并从点云图中选取了250条剖面线,计算了剖面线的高度均方根,高度偏度,高度峰度,坡度均值,坡度均方根,坡度偏度,坡度峰度等统计量。高度均方根,坡度均方根和相关长度分别为0.090 m, 0.075 和 11.74 m。从所选取的5个样本来看,有3个样本(150条剖面线)的高度分布为高斯分布,所有样本的坡度分布都为指数分布。另外,我们也计算了分形维度和功率谱密度。结果显示,渤海沿岸固定冰的分形维度约为1.132。选取的250条剖面线的功率谱密度与指数自相关函数功率谱密度更接近。Abstract: The surface roughness characteristics (e.g., height and slope) of sea ice are critical for determining the parameters of an electromagnetic scattering, a surface emission and a surface drag coefficients. It is also important in identifying various ice types, retrieval ice thickness, surface temperature and drag coefficients from remote sensing data. The point clouds (a set of points which are usually defined by X, Y, and Z coordinates that represents the external surface of an object on earth) of land fast ice in five in situ sites in the eastern coast Bohai Sea were measured using a laser scanner-Trimble GX during 2011-2012 winter season. Two hundred and fifty profiles selected from the point clouds of different samples have been used to calculate the height root mean square, height skewness, height kurtosis, slope root mean square, slope skewness and slope kurtosis of them. The root mean square of the height, the root mean square of the slope and the correlation length are about 0.090, 0.075 and 11.74 m, respectively. The heights of 150 profiles in three sites manifest the Gaussian distribution and the slopes of total 250 profiles distributed exponentially. In addition, the fractal dimension and power spectral density profiles were calculated. The results show that the fractal dimension of land fast ice in the Bohai Sea is about 1.132. The power spectral densities of 250 profiles can be expressed through an exponential autocorrelation function.
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Key words:
- sea ice /
- roughness /
- statistical parameters /
- fractal dimension /
- spectral density
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