2017-2018年冬季乌梁素海湖冰表面裂缝形态分析

Analysis of ice cracks morphology on lake surface of Lake Wuliangsuhai in the winter of 2017-2018

在2017-2018年冬季使用无人机对乌梁素海湖冰的冰面裂缝进行了航拍,采用改进的自适应阈值分割方法进行图像二值化处理,提取了冰裂缝的密度和分形维数。分析结果显示:在固定区域的冰裂缝分形维数在1.35~1.50间变化,冰裂缝数量随时间增加,其分形维数也随之线性增大;在冰生长期间,冰厚度与冰裂缝分形维数也呈现出明显的线性关系(相关系数R^2=0.75)。冰面不同区域的冰裂缝密度和分形维数在0.017~0.079、1.38~1.64间变化,且两者之间存在显著的对数相关性(相关系数R^2>0.96),不同日期航拍数据拟合结果近似相等,说明冰裂缝密度越大,对应的分形维数越大。作为表征冰面形态特征的一种物理指标,建立得到的冰裂缝分形维数与冰厚、裂缝密度的相关关系,对未来利用冰面裂缝形态监测冰层的生消过程可提供科学的参考。

In the winter of 2017 and 2018,aerial photography of ice surface on Lake Wuliangsuhai was used to determine the density and fractal dimension of the cracks on ice surface,by using improved adaptive-thresholding and image segmentation.The results show that the fractal dimension of ice cracks at a fixed location changes within the range of 1.35~1.50,and both the amount and fractal dimension of the cracks increase with time.An obvious linear relationship is found between the fractal dimension and the ice thickness during the period of ice growth,with a correlation coefficient of R^2=0.75.For ice cracks at different locations of ice surface,the density varies within0.017~0.079,and fractal dimension within 1.38~1.64.A significant logarithmic relationship is also found between the two parameters,with a correlation coefficient of R^2>0.96.Aerial photographs in different days give very similar results of curve fitting,revealing that a larger crack density attributes to a larger fractal dimension of the cracks.As a physical index of ice surface morphology,the relationship between fractal dimension of ice cracks and ice thickness,crack density is developed in this study,which provide a possibility to monitor the ice growth and decay through the evolution of cracks on ice surface.