In climate models, the subgrid‐scale orography (SSO) parameterization imposes a blocked flow drag at low levels that is opposed to the local flow. In IPSL‐CM6A‐LR, an SSO lift force is also applied perpendicular to the local flow to account for the effect of locally blocked air in narrow valleys. Using IPSL‐CM6A‐LR sensitivity experiments, it is found that the tuning of both effects strongly impacts the atmospheric circulation. Increasing the blocking and reducing the lift lead to an equatorward shift of the Northern Hemisphere subtropical jet and a reduction of the midlatitude eddy‐driven jet speed. It also improves the simulated synoptic variability, with a reduced storm‐track intensity and increased blocking frequency over Greenland and Scandinavia. Additionally, it cools the polar lower troposphere in boreal winter. Transformed Eulerian Mean diagnostics also show that the low‐level eddy‐driven subsidence over the polar region is reduced consistent with the simulated cooling. The changes are amplified in coupled experiments when compared to atmosphere‐only experiments, as the low‐troposphere polar cooling is further amplified by the temperature and albedo feedbacks resulting from the Arctic sea ice growth. In IPSL‐CM6A‐LR, this corrects the warm winter bias and the lack of sea ice that were present over the Arctic before adjusting the SSO parameters. Our results, therefore, suggest that the adjustment of SSO parameterization alleviates the Arctic sea ice bias in this case. However, the atmospheric changes induced by the parametrized SSO also impact the ocean, with an equatorward shift of the Northern Hemisphere oceanic gyres and a weaker Atlantic meridional overturning circulation.

中文翻译：

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通过修改亚网格尺度地形参数化来缓解耦合模型中的北极海冰偏差


在气候模型中，亚网格尺度地形（SSO）参数化在低水平上施加了与局部流动相反的阻塞流动阻力。在 IPSL-CM6A-LR 中，SSO 升力也垂直于局部流动施加，以考虑狭窄山谷中局部阻塞空气的影响。使用 IPSL-CM6A-LR 敏感性实验发现，两种效应的调节都会强烈影响大气环流。阻挡的增加和升力的减少导致北半球副热带急流向赤道方向移动，中纬度涡流驱动的急流速度降低。它还改善了模拟的天气变化，降低了格陵兰岛和斯堪的纳维亚半岛的风暴路径强度并增加了阻塞频率。此外，它在北方冬季使极地对流层低层变冷。变换欧拉平均诊断还表明，极地地区低水平涡流驱动的沉降有所减少，与模拟冷却一致。与仅大气实验相比，耦合实验中的变化被放大，因为北极海冰生长引起的温度和反照率反馈进一步放大了低对流层极地冷却。在 IPSL-CM6A-LR 中，这纠正了调整 SSO 参数之前北极上空存在的暖冬偏差和海冰缺乏。因此，我们的结果表明，SSO 参数化的调整减轻了这种情况下的北极海冰偏差。然而，参数化 SSO 引起的大气变化也会影响海洋，导致北半球海洋环流向赤道移动，大西洋经向翻转环流减弱。