Summertime atmosphere–sea ice coupling in the Arctic simulated by CMIP5/6 models: Importance of large-scale circulation
Summertime atmosphere–sea ice coupling in the Arctic simulated by CMIP5/6 models: Importance of large-scale circulation
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DOI：
10.1007/s00382-020-05543-5
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发表时间：
2021-01
期刊：
影响因子：
4.6
通讯作者：
Rui Luo;Q. Ding;Zhiwei Wu;Ian Baxter;M. Bushuk;Yiyi Huang;Xiquan Dong
中科院分区：
文献类型：
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作者：
Rui Luo;Q. Ding;Zhiwei Wu;Ian Baxter;M. Bushuk;Yiyi Huang;Xiquan Dong
北极夏季正压高压及其在海冰上引起的更温暖和更湿润的大气被认为是过去几十年年际和年代际时间尺度上九月海冰损失的重要因素。利用 ERA5 和其他再分析数据，我们发现北极大气变暖和湿润，与高纬度大气环流变化同步，通过增加地表下流长波辐射协同作用，融化海冰。 CMIP5 和 6 能够在多大程度上捕获这种大气-长波辐射-海冰关系仍然未知，因此解决这个问题是本研究的目的。为了实现这一目标，我们构建了一个面向过程的指标，强调大气温度和湿度与海冰之间的统计关系，可以有效地对 30 个 CMIP5 气候模型在再现观测到的联系方面的表现进行排名和区分。根据我们的评估，我们认为 CMIP5 和 6 中的大多数可用模型在再现观测到的大气-海冰连接的全部强度方面存在局限性。这种限制可能源于下流长波辐射在将海冰与环流联系起来时的微弱影响，而这与北极的温度和湿度场对环流变化的敏感性较弱有关。因此，应进一步努力了解这些模型局限性的根源，并提高模拟北极夏季期间将温度、湿度、表面辐射和海冰耦合在一起的大气环流影响的技能。
Summertime barotropic high pressure in the Arctic and its induced warmer and wetter atmosphere over sea ice are suggested to be important contributors to September sea ice loss on interannual and interdecadal time scales in the past decades. Using ERA5 and other reanalysis data, we find that atmospheric warming and moistening in the Arctic, synchronized by high latitude atmospheric circulation variability, work in tandem to melt sea ice through increasing downwelling longwave radiation at the surface. To what extent this atmosphere-longwave radiation-sea ice relationship can be captured in CMIP5 and 6 remains unknown and thus addressing this question is the objective of this study. To achieve this goal, we construct a process-oriented metric emphasizing the statistical relationship between atmospheric temperature and humidity with sea ice, which can effectively rank and differentiate the performance of 30 CMIP5 climate models in reproducing the observed connection. Based on our evaluation, we suggest that most available models in CMIP5 and 6 have a limitation in reproducing the full strength of the observed atmosphere–sea ice connection. This limitation likely stems from a weak impact of downwelling longwave radiation in linking sea ice with circulation associated with the weak sensitivity of the temperature and humidity fields to circulation variability in the Arctic. Thus, further efforts should be devoted to understanding the sources of these models’ limitations and improve skill in simulating the effects of atmospheric circulation in coupling temperature, humidity, surface radiation and sea ice together during Arctic summer.