The parametrization of orographic drag processes is a major source of circulation uncertainty in models. The COnstraining ORographic Drag Effects (COORDE) project makes a coordinated effort to narrow this uncertainty by bringing together the modeling community to: explore the variety of orographic drag parametrizations employed in current operational models; assess the resolution sensitivity of resolved and parametrized orographic drag across models; and to validate the parametrized orographic drag in low‐resolution simulations using explicitly resolved orographic drag from high‐resolution simulations. Eleven models from eight major modeling centers are used to estimate resolved orographic drag from high‐resolution (km‐scale) simulations and parametrized orographic drag from low‐resolution simulations, typically used for seasonal forecasting (∼40 km) and climate projections (∼100 km). In most models, at both seasonal and climate resolutions, the total (resolved plus parametrized) orographic gravity wave drag over land is shown to be underestimated by a considerable amount (up to 50%) over the Northern and Southern Hemisphere and by more than 60% over the Middle East region, with respect to the resolved gravity wave drag estimated from km‐scale simulations. The km‐scale simulations also provide evidence that the parametrized surface stress and the parametrized low‐level orographic drag throughout the troposphere are overestimated in most models over the Middle East region, particularly at climate resolutions. Through this process‐based evaluation, COORDE provides model developers new valuable information on the current representation of orographic drag at seasonal and climate resolutions and the vertical partitioning of orographic low‐level and gravity wave drag.

中文翻译：

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COnstraining地形阻力效应（COORDE）：已解析和参数化地形阻力的模型比较

地形阻力过程的参数化是模型中循环不确定性的主要来源。COnstraining地形阻力效应（COORDE）项目通过将建模社区召集在一起来做出协调一致的努力，以缩小这种不确定性：探索当前操作模型中采用的各种地形阻力参数化方法；评估跨模型的解析和参数化地形阻力的分辨率敏感性；并使用高分辨率模拟中明确解析的地形阻力来验证低分辨率模拟中的参数化地形阻力。来自八个主要建模中心的11个模型用于估算高分辨率（千米规模）模拟的解析地形阻力，以及根据低分辨率模拟估算的地形阻力（通常用于季节性预报（〜40公里）和气候预测（〜100公里）。在大多数模型中，在季节和气候分辨率下，显示的地形重力总波（已分解和参数化）在北半球和南半球均被低估了多达50％，且被低估了多达60％相对于通过千米规模模拟估算的已分解重力波阻力在中东地区所占的百分比。公里尺度的模拟还提供了证据，证明在整个中东地区的大多数模型中，特别是在气候分辨率方面，高估了整个对流层的参数化表面应力和参数化的低空地形阻力。通过基于过程的评估，