Assessments of the Climate System Model (CAS-ESM-C) Using IAP AGCM4 as Its Atmospheric Component
Assessments of the Climate System Model (CAS-ESM-C) Using IAP AGCM4 as Its Atmospheric Component
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发表时间：
2012
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通讯作者：
Hongchuan Sun
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作者：
Hongchuan Sun
本文评估了一个新的气候系统模式CAS-ESM-C（中国科学院-地球系统模式-气候系统组件）的性能，该模式采用了最近改进的IAP AGCM版本，即IAP AGCM 4作为其大气组件。本文首先简要介绍了模式的发展和框架，然后评价了模式在模拟大气、陆面、海洋和海冰的气候平均状态方面的性能。还分析了季节循环和年际变化的一些方面。结果表明，CAS-ESM-C模式成功地控制了长期气候漂移，并在真实再现大气、海洋、陆地表面和海冰的气候平均状态方面具有可接受的性能。CAS-ESM-C还成功地再现了热带太平洋海温的季节性变化和北极海冰覆盖的季节性变化。模式较好地再现了季风雨带的季节性迁移，表明模式对东亚季风的模拟效果是可以接受的。除了对ENSO周期的低估和对平均振幅的高估外，CAS-ESM-C模式较好地再现了热带太平洋年际变化的其他特征。特别重要的是，由于对热带太平洋海温季节循环的模拟，在模拟的ENSO中出现了其它耦合模式难以再现的“锁相”现象。CAS-ESM-C模式的主要缺陷是热带偏置，这在其他耦合模式中是常见的。分析了模拟偏差尤其是热带偏差产生的可能原因。结果表明，海气反馈放大的大气偏差是耦合系统中热带偏差产生的主要原因。根据偏差分析，CAS-ESM-C未来的改进方向应集中在AGCM中云和降水物理过程的处理上。从这一点来看，更新或改进低层云方案和大气模式的对流参数化可能是CAS-ESM-C未来发展的第一步。
This paper assesses the performance of a new climate system model, namely CAS-ESM-C (Chinese Academy of Sciences-Earth System Model-Climate system component), which employs the recently improved version of IAP AGCM, namely IAP AGCM4, as its atmospheric component. This paper first describes the development and framework of the model briefly, and then evaluates the performances of the model in simulating the climate mean states of the atmosphere, land surface, ocean, and sea ice. Some aspects of the seasonal cycle and interannual variability are also analyzed. The results indicate that the CAS-ESM-C succeeds in controlling the long-term climate drift and has acceptable performances in realistically reproducing the climate mean states of the atmosphere, ocean, land surface and sea ice. The CAS-ESM-C also successfully reproduces the seasonal cycle of SST over the tropical Pacific and the seasonal cycle of the sea ice cover in the Arctic. The seasonal migration of monsoon rain band is well reproduced in the model, indicating the acceptable performance of the East Asian monsoon simulation. Except for the slight underestimation of the ENSO period and overestimation of the average amplitude, other characteristics of interannual variability over the tropical Pacific are well reproduced in the CAS-ESM-C. It is particularly important that, benefiting from the realistic simulation of the seasonal cycle of SST over the tropical Pacific, a "phase-locked" phenomenon appears in the simulated ENSO, which is hardly reproduced in other coupled models. The main deficiency of the CAS-ESM-C is the tropic bias, which is common in other coupled models. Some analyses are made to reveal the possible reason behind these simulation biases especially the tropical bias. The results suggest that the biases in the atmosphere which are amplified by the ocean-atmosphere feedback are the key reasons of the tropic bias in the coupled system. According to the analyses of the biases, future improvements of the CAS-ESM-C should focus on the treatment of physical processes of cloud and precipitation in the AGCM. From this point, updating or improving the low-level cloud scheme and the convective parameterization of the atmosphere model may be the first step for the future development of the CAS-ESM-C.