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Process-Based Climate Model Development Harnessing Machine Learning: II. Model Calibration From Single Column to Global
Journal of Advances in Modeling Earth Systems ( IF 6.8 ) Pub Date : 2020-12-04 , DOI: 10.1029/2020ms002225
Frédéric Hourdin 1 , Daniel Williamson 2, 3 , Catherine Rio 4 , Fleur Couvreux 4 , Romain Roehrig 4 , Najda Villefranque 4 , Ionela Musat 1 , Laurent Fairhead 1 , F. Binta Diallo 1 , Victoria Volodina 3
Affiliation  

We demonstrate a new approach for climate model tuning in a realistic situation. Our approach, the mathematical foundations and technical details of which are given in Part I, systematically uses a single-column configuration of a global atmospheric model on test cases for which reference large-eddy-simulations are available. The space of free parameters is sampled running the single-column model from which metrics are estimated in the full parameter space using emulators. The parameter space is then reduced by retaining only the values for which the emulated metrics match large eddy simulations within a given tolerance to error. The approach is applied to the 6A version of the LMDZ model which results from a long investment in the development of physics parameterizations and by-hand tuning. The boundary layer is revisited by increasing the vertical resolution and varying parameters that were kept fixed so far, which improves the representation of clouds at process scale. The approach allows us to automatically reach a tuning of this modified configuration as good as that of the 6A version. We show how this approach helps accelerate the introduction of new parameterizations. It allows us to maintain the physical foundations of the model and to ensure that the improvement of global metrics is obtained for a reasonable behavior at process level, reducing the risk of error compensations that may arise from over-fitting some climate metrics. That is, we get things right for the right reasons.

中文翻译:

利用机器学习的基于过程的气候模型开发:II。从单列到全局的模型校准

我们展示了一种在现实情况下调整气候模型的新方法。我们的方法(其数学基础和技术细节在第 I 部分中给出)系统地使用了全球大气模型的单列配置,用于测试案例,这些案例的参考大涡模拟可用。运行单列模型对自由参数空间进行采样,从中使用模拟器在完整参数空间中估计指标。然后通过仅保留模拟度量与给定误差容限内的大涡模拟匹配的值来减少参数空间。该方法应用于 LMDZ 模型的 6A 版本,该模型源于对物理参数化和手动调整开发的长期投资。通过增加垂直分辨率和迄今为止保持固定的变化参数来重新访问边界层,这改进了过程尺度云的表示。该方法使我们能够自动对这种修改后的配置进行与 6A 版本一样好的调整。我们展示了这种方法如何帮助加速引入新的参数化。它使我们能够维护模型的物理基础,并确保在过程级别为合理行为获得全局指标的改进,从而降低可能因某些气候指标过度拟合而产生的误差补偿风险。也就是说,我们出于正确的原因把事情做好。该方法使我们能够自动对这种修改后的配置进行与 6A 版本一样好的调整。我们展示了这种方法如何帮助加速引入新的参数化。它使我们能够维护模型的物理基础,并确保在过程级别为合理行为获得全局指标的改进,从而降低可能因某些气候指标过度拟合而产生的误差补偿风险。也就是说,我们出于正确的原因把事情做好。该方法使我们能够自动对这种修改后的配置进行与 6A 版本一样好的调整。我们展示了这种方法如何帮助加速引入新的参数化。它使我们能够维护模型的物理基础,并确保在过程级别为合理行为获得全局指标的改进,从而降低可能因某些气候指标过度拟合而产生的误差补偿风险。也就是说,我们出于正确的原因把事情做好。它使我们能够维护模型的物理基础,并确保在过程级别为合理行为获得全局指标的改进,从而降低可能因某些气候指标过度拟合而产生的误差补偿风险。也就是说,我们出于正确的原因把事情做好。它使我们能够维护模型的物理基础,并确保在过程级别为合理行为获得全局指标的改进,从而降低可能因某些气候指标过度拟合而产生的误差补偿风险。也就是说,我们出于正确的原因把事情做好。
更新日期:2020-12-04
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