Application of fluid mechanical technique to the analysis of ice movements in Okhotsuk Sea using satellite millimeter radar images

基于DMSP卫星上SSM/I传感器获取的毫米雷达图像，采用图像相关PIV方法对鄂霍和锡克海海冰运动进行了研究。冬季，由于鄂和锡克海的云层很厚，很难用可见光观测冰，但毫米雷达图像可以透过厚厚的云层进行观测。从美国国家冰雪数据中心获取37GHz和85GHz雷达图像，然后对远海云图进行平滑和消除，消除针孔噪声，得到清晰的图像。利用这些清晰的图像，研究了过去几年的冰运动，以区分海冰多的年份和海冰少的年份的特征。然后利用相关PIV对冰原内部区域和周边区域冰的运动进行比较，估算出冰原产生的区域。在进行PIV分析之前，还考虑了分析矩阵形状等条件，并将本方法的可追溯性与1994年GPS信标的跟踪结果进行了比较，以保证本方法的可靠性。结果发现：1)西北季节性风的强度决定了每年海冰的数量；2)北海道附近每年都有海冰形成旋涡状结构；3)俄罗斯东海岸附近的冰原在强烈而极冷的季节性西北风的作用下与海岸分离形成开阔的海域，海面立即冻结形成新的海冰。

Sea ice movements in Okhotsuk Sea were investigated based on millimeter radar images obtained by SSM/I sensors on board DMSP satellite by means of image correlation PIV method. Due to the thick clouds covering the Okhotsuk Sea in winter, investigation of ice via visible light is difficult, but the millimeter radar images can see through the thick clouds and enable us the investigation. 37GHz and 85GHz radar images were obtained from National Snow and Ice Data Center in U.S.A. Then in order to obtain clear images, pinhole noises were eliminated followed by smoothing and elimination of cloud's images on open sea. Using these clear images, ice movement in the past several years were investigated to differentiate the characteristics between years of more sea ice and less sea ice. Then movements of ice in the inner region of ice field and the perimeter were compared by means of correlation PIV to estimate the region of ice production. Also prior to PIV analysis, conditions such as the shape of analyzing matrix were considered, and traceability of present PIV method is compared with tracking results of GPS beacon conducted 1994 to ensure the reliability of present PIV method. As the results, 1) strength of north-westerly seasonal wind was found to determine the amount of sea ice in each year, 2) sea ice was found to form vortex like structure near Hokkaido in every year, 3) ice field near Russian east coast was found to detach from the coast to create open sea region by strong and extremely cold seasonal north-westerly wind, and immediately the sea surface is frozen to create new sea ice.