Arctic PASSION - High Resolution Synthetic Aperture Radar based Risk Index Outcome (AP-RIO)

The Risk Index Outcome (RIO) is a critical component of the Polar Operational Limit Assessment Risk Indexing System (POLARIS) developed by the International Maritime Organization (IMO, 2016). RIO evaluates the operational risks for ships navigating in ice-infested waters by evaluating ice conditions and offers a quantifiable measure of risk that aids in decision-making for safe navigation in polar regions based on ship ice class, sea ice type/stage of development (SOD) and sea ice concentration (SIC). The DMI-led Automated Sea Ice Products (DMI-ASIP; Wulf et al., 2024, dataset) provides daily maps of SOD and SIC based on Sentinel-1 SAR imagery, AMSR-2 Passive Microwave and Ice Charts from the Greenland and Canadian Ice Services, combined with novel AI retrieval and processing techniques. In the framework of EU funded Arctic PASSION project, we produced 10 years of satellite observation based weekly RIO maps referred as the Arctic PASSION-RIO (AP-RIO) by leveraging DMI-ASIP datasets. The AP-RIO dataset will provide weekly risk assessment maps for the given ship classes and will support the establishment of a 10 year climatology thereby enabling the assessment of RIO variability in the years covered by the input DMI-ASIP products. The AP-RIO dataset will enhance the safety and efficiency of maritime operations in the polar seas, providing a robust reference for evaluating normal and extreme ice conditions. AP-RIO is produced in the framework of the Arctic PASSION project (European Union's Horizon 2020 research and innovation program under grant agreement No. 101003472) and supported by the DMI-ASIP development team.Algorithm and Processing Scheme:SIC and SOD from ASIP are processed (by taking the mean and mode respectively) into a weekly field based on the daily files for that week. This is done for the time period of 3 Oct. 2014 - 3 Oct. 2024. The weekly SOD is used to find the Risk Value (RV) by looking at the lookup table (Dybkjær et al. 2025a). Risk Index Outcome (RIO) values are computed for each pixel in the field based on the RIO formula (RIO = SIC x RV) using the SIC from ASIP and the found RV. The meaning of the computed RIO values can be interpreted using the table in (Dybkjær et al. 2025b). The RIO field is finally saved to weekly NetCDF files.

风险指数结果（Risk Index Outcome，简称RIO）是国际海事组织（International Maritime Organization, IMO, 2016）研发的极地作业极限评估风险指数系统（Polar Operational Limit Assessment Risk Indexing System, POLARIS）的核心组成部分。RIO通过评估冰况，为航行于冰区水域的船舶评估作业风险，并提供可量化的风险度量，助力基于船舶冰级、海冰类型/发展阶段（Sea Ice Type/Stage of Development, SOD）和海冰密集度（Sea Ice Concentration, SIC）的极地安全航行决策。
由丹麦气象研究所（DMI）主导研发的自动化海冰产品（Automated Sea Ice Products, DMI-ASIP；Wulf等，2024，数据集）基于哨兵-1号（Sentinel-1）合成孔径雷达（Synthetic Aperture Radar, SAR）影像、AMSR-2被动微波数据以及格陵兰岛与加拿大冰务部门的冰况图，结合新型人工智能检索与处理技术，生成SOD与SIC的每日分布图。
在欧盟资助的北极PASSION项目框架下，研究团队依托DMI-ASIP数据集，生成了基于10年卫星观测数据的周度RIO分布图，命名为北极PASSION-RIO（Arctic PASSION-RIO, AP-RIO）。AP-RIO数据集将为指定船舶冰级提供周度风险评估分布图，并助力构建10年海冰气候数据集，从而能够基于输入的DMI-ASIP产品覆盖时段，评估RIO的时空变异性。AP-RIO数据集将提升极地海域海事作业的安全性与作业效率，为评估常规与极端冰况提供可靠的参考依据。AP-RIO数据集由北极PASSION项目（欧盟“地平线2020”研究与创新计划，资助协议编号101003472）框架下研发，并得到DMI-ASIP开发团队的支持。
算法与处理流程：从ASIP获取的SIC与SOD数据，分别通过取均值和众数的方式，基于当周的每日文件生成周度格点场。该处理覆盖的时间范围为2014年10月3日至2024年10月3日。通过查询查找表（Dybkjær等，2025a），利用周度SOD数据获取风险值（Risk Value, RV）。基于RIO计算公式（RIO = SIC × RV），利用ASIP提供的SIC数据与获取的RV值，为格点场中的每个像素计算RIO值。可通过Dybkjær等（2025b）中的表格对计算得到的RIO值进行解译。最终，生成的RIO格点场将保存为周度NetCDF格式文件。