CoAuthors

Ran Yan (Qingdao University, China); Xi Zhang (First Institute of Oceanography, China); Ying Xu (National Satellite Ocean Application Service, China); Ping Chen (Huazhong University of Science and Technology, China); Yongsen Zhao (Qingdao University, China); Yuexiang Guo (Qingdao University, China); Yangeng Chen (Qingdao University, China); Xiaohan Zhang (Qingdao University, China); Shengxu Li (Qingdao University, China)

Sea ice recognition is one of the main tasks for sea ice monitoring in the Arctic and is also applied for the detection of other ocean phenomena. The Surface Wave Investigation and Monitoring (SWIM) instrument, as an innovative remote sensor that operates at multiple small incidence angles, is different from existing sensors with moderate and normal incidence modes for sea ice monitoring. Sea ice recognition at small incidence angles has rarely been studied. Moreover, SWIM uses a discrimination flag of sea ice and sea water to remove sea ice from sea wave products. Therefore, this research focuses on sea ice recognition in the Arctic based on SWIM data from October 2020 to April 2021. Eleven features are first extracted, and applied for the analysis of the waveform characteristics using the cumulative probability distribution and mutual information measurement. Random forest (RF), k-nearest neighbor (KNN) and support vector machine (SVM) classifiers are built, and their abilities to distinguish between sea ice and sea water are assessed. The optimal classifier is the KNN method with Euclidean distance and k equal to 11. Feature combinations are also used to separate sea ice and sea water based on the KNN method to select the optimal combination. Thus, the optimal classifier-feature assembly at each small incidence angle is established, and the highest overall accuracy reaches 97.1%. These results reveal that SWIM performs very well in sea ice recognition. Moreover, the application of the optimal classifier–feature assemblies is studied, and its performance is fairly good. These assemblies yield high accuracies in the short- and long-term periods of sea ice recognition and satisfy the SWIM requirement of removing the sea ice effect. Moreover, sea ice extents and edges can be extracted from SWIM sea ice recognition results at a high level of precision. As a result, the optimal classier–feature assemblies based on SWIM data express the effectiveness of the SWIM approach in sea ice recognition. Our work not only highlights the new sea ice monitoring technology of remote sensing at small incidence angles, but also studies the application of SWIM data in sea ice services.