Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition
Nudging allows direct evaluation of coupled climate models with in situ observations: a case study from the MOSAiC expedition
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DOI：
10.5194/gmd-16-1857-2023
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发表时间：
2023-04
影响因子：
5.1
通讯作者：
F. Pithan;Marylou Athanase;S. Dahlke;A. Sánchez-Benítez;M. Shupe;A. Sledd;J. Streffing;G. Svensson;T. Jung
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作者：
F. Pithan;Marylou Athanase;S. Dahlke;A. Sánchez-Benítez;M. Shupe;A. Sledd;J. Streffing;G. Svensson;T. Jung
抽象的。将大气环流模式的输出与观测结果进行比较对于评估和提高模式的质量至关重要。虽然数值天气预报模型通常是根据大量的观测结果进行评估的，但比较气候模型和观测结果通常需要很长的时间序列来建立可靠的统计数据。在这里，我们表明，通过轻推耦合气候模型中的大尺度大气环流，模型输出可以与个别日子的当地观测进行比较。我们在2020年4月的一段时间内为三个气候模型说明了这一点，当时暖空气入侵到达了北极中部的MOSAiC（北极气候研究多学科漂流观测站）探险队。MOSAiC考察的无线电探空仪、云遥感和地面通量观测可作为参考观测。气候模式AWI-CM 1/ECHAM和AWI-CM 3/IFS在春季错过了地表温度的日变化周期，这可能是因为两个模式都假设冰上的积雪具有均匀的温度。CAM 6是一个使用三层来表示雪温的模型，它更真实地表示了日循环。在寒冷和干燥的时期，广泛的薄的混合相云，AWI-CM 1/ECHAM只产生部分云量和高估下降流短波辐射的表面。AWI-CM 3/IFS产生封闭的云层覆盖，但错过了云的液态水。我们的研究结果表明，轻推大尺度环流的观测状态允许一个有意义的比较气候模式的输出，即使是短期的观测活动。我们认为，轻推可以简化和加速从观测到气候模式改进的途径，并大大扩展了适合模型评估的观测范围。
Abstract. Comparing the output of general circulation models to observations is essential for assessing and improving the quality of models. While numerical weather prediction models are routinely assessed against a large array of observations, comparing climate models and observations usually requires long time series to build robust statistics. Here, we show that by nudging the large-scale atmospheric circulation in coupled climate models, model output can be compared to local observations for individual days. We illustrate this for three climate models during a period in April 2020 when a warm air intrusion reached the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) expedition in the central Arctic. Radiosondes, cloud remote sensing and surface flux observations from the MOSAiC expedition serve as reference observations. The climate models AWI-CM1/ECHAM and AWI-CM3/IFS miss the diurnal cycle of surface temperature in spring, likely because both models assume the snowpack on ice to have a uniform temperature. CAM6, a model that uses three layers to represent snow temperature, represents the diurnal cycle more realistically. During a cold and dry period with pervasive thin mixed-phase clouds, AWI-CM1/ECHAM only produces partial cloud cover and overestimates downwelling shortwave radiation at the surface. AWI-CM3/IFS produces a closed cloud cover but misses cloud liquid water. Our results show that nudging the large-scale circulation to the observed state allows a meaningful comparison of climate model output even to short-term observational campaigns. We suggest that nudging can simplify and accelerate the pathway from observations to climate model improvements and substantially extends the range of observations suitable for model evaluation.