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

利用DMSP卫星上的SSM/I传感器获取的毫米波雷达图像，采用图像相关PIV方法研究了鄂霍次海的海冰运动。由于冬季的鄂霍次海有厚厚的云层覆盖，通过可见光进行冰层调查很困难，但毫米雷达图像可以穿透厚厚的云层，使我们能够进行调查。从美国国家冰雪数据中心获得了37 GHz和85 GHz的雷达图像，为了获得清晰的图像，先去除针孔噪声，然后对外海云层图像进行平滑和消除。利用这些清晰的图像，研究了过去几年的冰运动，以区分海冰较多和海冰较少的年份的特征。在此基础上，利用相关PIV方法比较冰场内区和周界的冰运动，从而判断出冰雪产生区。在进行PIV分析之前，还考虑了分析矩阵的形状等条件，并将本PIV方法的可跟踪性与1994年GPS信标的跟踪结果进行了比较，以确保本PIV方法的可靠性。结果表明：1)西北季风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涡状结构；3)俄罗斯东海岸附近的冰场在季风和季风的作用下脱离海岸，形成开阔海区，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.