An overview of the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts
An overview of the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts
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DOI：
10.1007/s00382-020-05409-w
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发表时间：
2020-08
期刊：
影响因子：
4.6
通讯作者：
I. Richter;H. Tokinaga
中科院分区：
文献类型：
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作者：
I. Richter;H. Tokinaga
研究了耦合模式相互比较项目第6阶段（CMIP 6）的大气环流模式模拟热带大西洋的平均状态和变率及其与热带太平洋的联系的能力。虽然平均而言，相对于之前的相互比较（CMIP 5），平均状态偏差几乎没有改善，但现在有一些模型的偏差非常小。特别是赤道大西洋暖SST和西风偏差在这些模式中大多被消除。此外，在赤道和亚热带大西洋的年际变化是相当现实的一些CMIP6模式，这表明他们应该是有用的工具，了解和预测的变化模式。赤道大西洋偏差的演变遵循与前几代模型相同的模式，西风偏置在北方春季之前温暖的海表温度（SST）偏置在东部在北方夏季。西风偏置的很大一部分已经存在于大气中，只有模拟强迫与观测到的SST，这表明大气起源。虽然在许多模式中的变化是相对现实的，SST似乎不太响应风强迫比观察到的，无论是在赤道和亚热带，可能是由于一个过深的混合层起源于海洋组件。因此，具有真实SST振幅的模型往往具有过大的风振幅。具有最小平均状态偏差的模型都具有相对较高的分辨率，但也有一些低分辨率模型表现同样出色，这表明分辨率并不是减少热带大西洋偏差的唯一方法。结果还表明，平均状态偏差和模拟变异性的质量之间的联系相对较弱。与热带太平洋的联系显示了各种模式的行为，表明需要进一步改进模式。
General circulation models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are examined with respect to their ability to simulate the mean state and variability of the tropical Atlantic and its linkage to the tropical Pacific. While, on average, mean state biases have improved little, relative to the previous intercomparison (CMIP5), there are now a few models with very small biases. In particular the equatorial Atlantic warm SST and westerly wind biases are mostly eliminated in these models. Furthermore, interannual variability in the equatorial and subtropical Atlantic is quite realistic in a number of CMIP6 models, which suggests that they should be useful tools for understanding and predicting variability patterns. The evolution of equatorial Atlantic biases follows the same pattern as in previous model generations, with westerly wind biases during boreal spring preceding warm sea-surface temperature (SST) biases in the east during boreal summer. A substantial portion of the westerly wind bias exists already in atmosphere-only simulations forced with observed SST, suggesting an atmospheric origin. While variability is relatively realistic in many models, SSTs seem less responsive to wind forcing than observed, both on the equator and in the subtropics, possibly due to an excessively deep mixed layer originating in the oceanic component. Thus models with realistic SST amplitude tend to have excessive wind amplitude. The models with the smallest mean state biases all have relatively high resolution but there are also a few low-resolution models that perform similarly well, indicating that resolution is not the only way toward reducing tropical Atlantic biases. The results also show a relatively weak link between mean state biases and the quality of the simulated variability. The linkage to the tropical Pacific shows a wide range of behaviors across models, indicating the need for further model improvement.