Understanding and Seeking Ways to Improve the Capability of Models in Simulating a Key Climate Pattern of the Northern Hemisphere


The warm Arctic–cold Eurasia (WACE) climate pattern is the main feature of winter temperature in the Northern Hemisphere in the last 20 years. Extreme cold events related to this pattern have occurred frequently in the Northern Hemisphere, causing large numbers of human casualties and considerable economic losses. The ability of climate models to simulate WACE directly affects the skill in simulating the winter temperature. Past studies have shown that previous generations of climate models were poor at simulating the midlatitude atmospheric response to sea ice, resulting in them simulating a weaker than observed WACE. However, it is unclear whether the situation has improved for the current generation of state-of-the-art climate models (i.e., models participating in phase 6 of the Coupled Model Intercomparison Project, or CMIP6).
Scientists from the Institute of Atmospheric Physics (Chinese Academy of Sciences), the China Meteorological Administration, and Nanjing University of Information Science and Technology, evaluated the ability of CMIP6 models to simulate WACE and suggested the key factors influencing the differences in simulation capability. The findings have recently been published in Advances in Atmospheric Sciences.
Results showed that the CMIP6 multi-model ensemble mean was better able to simulate WACE, but that there were still large gaps among individual models. Models with good ability in simulating the climatic states and extremes of Eurasian winter temperatures also showed more skill in simulating WACE.
"The difference in the simulation of extremes was mainly reflected in the ability to simulate the warming anomalies in the Barents Sea–Kara Sea (BKS) region," explains one of the authors of the paper, ZHAO Liang. 
Further analysis showed that the models' simulations of BKS warming anomalies were related to their reflection of the location and persistence of the Ural blocking (a large-scale anticyclone that occurs in the Ural Mountains region), which transmits heat northwards to the BKS, thereby warming the Arctic, strengthening the downstream westerly trough, and cooling central Eurasia. Therefore, the simulation of the Ural blocking is the key to improving the capability of climate models in simulating WACE.
Citation: Zhao, L., and Coauthors, 2023: The warm Arctic–cold Eurasia pattern and its key region in winter in CMIP6 model simulations. Adv. Atmos. Sci., https://doi.org/10.1007/s00376-022-2201-4 
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