Abstract JRA55-do, the new atmospheric dataset for driving ocean–sea-ice models based on the Japanese 55-year atmospheric reanalysis (JRA-55), has been recently proffered for use in future ocean–sea-ice hindcast simulations, including those under the Ocean Model Intercomparison Project (OMIP) umbrella, thereby replacing the Coordinated Ocean-ice Reference Experiments (CORE) interannual forcing dataset. The JRA55-do dataset contains numerous and substantial improvements over the existing CORE dataset, including refined resolution, self-consistency of forcing fields, and duration. However, one feature of CORE, that is not available in JRA55-do, is the “Normal Year Forcing” (CORE-NYF), a single repeating annual cycle of all forcing fields necessary to run an ocean–sea-ice model without imposed interannual variability. Here, we propose a process for obtaining and evaluating “Repeat Year Forcing” (RYF) datasets based on the JRA55-do dataset for driving ocean–sea-ice models. This process involves the identification of 12-month periods (not necessarily a single calendar year) that are most neutral in terms of major climate modes of variability. Three candidate periods are identified and evaluated with three global ocean–sea-ice models. We find that the largest differences between the simulations arise from model biases, indicating the ultimate choice of the candidate repeat year is not critical. By referencing to the respective CORE-NYF simulations (in an attempt to account for model bias), we find the differences between the three RYF periods to be generally consistent across the models, except for an anthropogenic warming signal for later candidate years. Based on the analysis presented here, we find all three candidate periods to be suitable for use as RYF datasets, subject to application, and we recommend the period from 1st May 1990 to 30th April 1991 to be the best available RYF dataset for driving ocean–sea-ice models.

中文翻译：

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用于驱动海洋-海冰模型的基于 JRA55 的重复年强迫数据集

摘要 JRA55-do 是基于日本 55 年大气再分析 (JRA-55) 的用于驱动海洋-海冰模型的新大气数据集，最近已被用于未来的海洋-海冰后报模拟，包括那些在海洋模式比对项目 (OMIP) 伞下，从而取代协调海冰参考实验 (CORE) 年际强迫数据集。JRA55-do 数据集包含对现有 CORE 数据集的大量实质性改进，包括改进的分辨率、强迫场的自洽性和持续时间。然而，在 JRA55-do 中没有的 CORE 的一个特征是“正常年强迫”（CORE-NYF），它是运行海洋-海冰模型所需的所有强迫场的单一重复年度循环，而没有施加任何强迫。年际变化。这里，我们提出了一种获取和评估基于 JRA55-do 数据集的“重复年强迫”（RYF）数据集的过程，用于驱动海洋-海冰模型。该过程涉及确定在主要气候变率模式方面最中性的 12 个月期间（不一定是单个日历年）。使用三个全球海洋-海冰模型确定和评估了三个候选时期。我们发现模拟之间的最大差异来自模型偏差，表明候选重复年份的最终选择并不重要。通过参考各自的 CORE-NYF 模拟（试图解释模型偏差），我们发现三个 RYF 时期之间的差异在模型中大体一致，除了后期候选年份的人为变暖信号。