海冰是海洋环境监测的重点对象，光学遥感能为海冰的精细化监测提供技术支持，实现海冰的动态监测与量化估算。中国海洋水色业务卫星星座——海洋一号C/D卫星（Haiyang-1C/D, HY-1C/D），搭载有适用于海冰监测的海岸带成像仪（Coastal Zone Imager, CZI）和水色水温扫描仪（Chinese Ocean Color and Temperature Scanner, COCTS），具备开展海冰业务化监测应用的能力。本研究以2021年12月至2022年3月中国渤海辽东湾海冰为例，收集了冰期内的HY-1C/D卫星影像数据，开展海冰识别与估算研究，评估CZI与COCTS数据对海冰的识别效能，分析海冰、海水、云等典型目标在光学（可见光-近红外）和热红外波段的影像特征；面向光学遥感影像中海冰识别易受到云干扰这一困扰，基于COCTS载荷热红外、近红外及红光波段数据，通过海冰与云的亮度温度及光谱反射差异实现云信息的区分和剔除；针对50 m空间分辨率CZI光学影像中的海冰海水像元混合问题，通过海冰密集度反演提高海冰面积的估算精度，并与哨兵2号卫星（Sentinel-2）多光谱影像数据（MultiSpectral Instrument，MSI）结果进行对比验证。研究结果表明：本研究方法针对HY-1C/D卫星影像数据中的海冰识别提取具有较高的精度和抗干扰能力，可为国产海洋光学卫星的海冰监测业务化应用提供方法参考。

Sea ice represents a typical natural phenomenon that affects the marine and coastal environment in North China, and thus being the focus of marine environment monitoring. Timely and accurate remote sensing data about sea ice (e.g., sea ice extent, area, and thickness) is of great importance for the emergency treatment and recovery. So far, various remote sensing technologies have been applied to sea ice monitoring. Among these optical remote sensing is frequently used, and sea ice concentration (SIC) is a key parameter indicating the spatial distribution characteristics of sea ice. However, it should be noted that sea ice and cloud have similar reflection characteristics in visible and near-infrared (VNIR) wavelengths, thus posing great difficulties for the optical extraction of sea ice. Haiyang-1C/D (HY-1C/D) satellites are the first operational ocean color satellites of China, both of them are equipped with Coastal Zone Imager (CZI) and Chinese Ocean Color and Temperature Scanner (COCTS), which can technically support the fine and dynamical monitoring of sea ice due to their wide coverage and high spatial and temporal resolution. In addition to the VNIR bands (412-865 nm), the COCTS sensor onboard can also interpret the thermal characteristics of targets, which would help distinguish between sea ice and cloud. In this study, Liaodong Bay of Bohai Sea is selected as the study area, and synchronous CZI and COCTS images covering Liaodong Bay from December, 2021 to March, 2022 are collected and analyzed. The main objective of this study is to verify the feasibility of HY-1C/D satellites to detect sea ice, especially the image characteristics of typical targets (i.e., sea ice, seawater and cloud) in both optical (i.e., VNIR) and thermal infrared bands. Based on the brightness temperature (BT) difference between sea ice and cloud in the thermal infrared band of COCTS, sea ice and cloud can be preliminarily separated. Then, sea ice can be distinguished from seawater due to its higher reflectance in VNIR wavelengths. Moreover, considering the mixed pixel effect of sea ice and seawater in optical images with different spatial resolution, the scale applicability of SIC is discussed comparing with near-synchronous Sentinel-2 MSI images with spatial resolution of 10 m. The results indicate that our method taking BT into consideration can effectively distinguish between sea ice and cirrus clouds, and shows good precision and anti-interference ability. However, there is little difference in BT between cumulus clouds and sea ice, which can be further separated according to the NIR-red reflectance ratio. In addition, the application of SIC can effectively unmix ice-water pixels and improve the estimation accuracy of sea ice area for optical images with spatial resolution lower than 50 m. The above results can confirm the capability of HY-1C/D satellites in sea ice detection. Therefore, HY-1C/D satellites can provide reliable data and improve the monitoring of sea ice.