Abstract As climate models move towards higher resolution, their ocean components are now able to explicitly resolve mesoscale eddies. High resolution for ocean models is roughly classified into eddy-present (EP, ∼ 1/4°) and eddy-rich (ER, ∼ 1/12°) resolution. The cost–benefit of ER resolution over EP resolution remains debated. To inform this discussion, we quantify and compare the surface properties of coherent mesoscale eddies in high-resolution versions of the HadGEM3-GC3.1 coupled climate model, using an eddy tracking algorithm. The modelled properties are compared to altimeter observations. Relative to EP, ER resolution simulates more (+60%) and longer-lasting (+23%) eddies, in better agreement with observations. The representation of eddies in Western Boundary Currents (WBCs) and the Southern Ocean compares well with observations at both resolutions. However a common deficiency in the models is the low eddy population in subtropical gyre interiors, which reflects model biases at the Eastern Boundary Upwelling Systems and at the Indonesian outflow, where most of these eddies are generated in observations. Despite a grid spacing larger than the Rossby radius of deformation at high-latitudes, EP resolution does allow for eddy growth in these regions, although at a lower rate than seen in observations and ER resolution. A key finding of our analysis is the large differences in eddy size across the two resolutions and observations: the median speed-based radius increases from 14 km at ER resolution to 32 km at EP resolution, compared with 48 km in observations. It is likely that observed radii are biased high by the effective resolution of the gridded altimeter dataset due to post-processing. Our results highlight the limitations of the altimeter products and the required caution when employed for understanding eddy dynamics and developing eddy parameterizations.

中文翻译：

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使用“存在涡流”和“富含涡流”的海洋分辨率评估耦合气候模拟中的表面涡流特性

摘要 随着气候模型朝着更高分辨率发展，它们的海洋成分现在能够明确地解析中尺度涡旋。海洋模型的高分辨率大致分为存在涡流 (EP, ∼ 1/4°) 和富涡流 (ER, ∼ 1/12°) 分辨率。ER 分辨率相对于 EP 分辨率的成本效益仍有争议。为了为讨论提供信息，我们使用涡流跟踪算法量化并比较了高分辨率版本的 HadGEM3-GC3.1 耦合气候模型中相干中尺度涡流的表面特性。将建模的属性与高度计观测值进行比较。相对于 EP，ER 分辨率模拟了更多 (+60%) 和更持久 (+23%) 的涡流，与观察结果更加吻合。西部边界流 (WBC) 和南大洋中涡旋的表现与两种分辨率下的观测结果相得益彰。然而，模型中的一个常见缺陷是亚热带环流内部的低涡群，这反映了东部边界上升流系统和印度尼西亚流出系统的模型偏差，其中大部分涡流是在观测中产生的。尽管网格间距大于高纬度地区的 Rossby 变形半径，但 EP 分辨率确实允许这些区域的涡流增长，尽管其速率低于观测和 ER 分辨率中所见。我们分析的一个关键发现是两种分辨率和观测值之间涡流大小的巨大差异：基于速度的中值半径从 ER 分辨率的 14 公里增加到 EP 分辨率的 32 公里，与 48 公里的观测相比。由于后处理，网格高度计数据集的有效分辨率可能会使观察到的半径偏高。我们的结果突出了高度计产品的局限性以及在用于理解涡流动力学和开发涡流参数化时需要注意的事项。