The Sensitivity of Euro‐Atlantic Regimes to Model Horizontal Resolution

• Published in: Geophysical research letters Vol. 46; no. 13; pp. 7810 - 7818
• Main Authors: Strommen, K., Mavilia, I., Corti, S., Matsueda, M., Davini, P., Hardenberg, J., Vidale, P.‐L., Mizuta, R.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 16.07.2019; John Wiley and Sons Inc
• Subjects: Atmospheric dynamics; Atmospheric models; Atmospheric Processes; Atmospheric Science; Bifurcations and Attractors; climate model; clustering; Computer simulation; Euro‐Atlantic; General Circulation; General circulation models; Geodesy and Gravity; Global Change; Global Climate Models; horizontal resolution; Nonlinear Geophysics; Ocean/Earth/atmosphere/hydrosphere/cryosphere interactions; Paleoceanography; Research Letter; Research Letters; Resolution; weather regimes
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2019GL082843

There is growing evidence that the atmospheric dynamics of the Euro‐Atlantic sector during winter is driven in part by the presence of quasi‐persistent regimes. However, general circulation models typically struggle to simulate these with, for example, an overly weakly persistent blocking regime. Previous studies have showed that increased horizontal resolution can improve the regime structure of a model but have so far only considered a single model with only one ensemble member at each resolution, leaving open the possibility that this may be either coincidental or model dependent. We show that the improvement in regime structure due to increased resolution is robust across multiple models with multiple ensemble members. However, while the high‐resolution models have notably more tightly clustered data, other aspects of the regimes may not necessarily improve and are also subject to a large amount of sampling variability that typically requires at least three ensemble members to surmount. Key Points Climate models have difficulty representing Euro‐Atlantic regime structure correctly Increasing horizontal resolution improves the significance of regime clustering across multiple models Spatial patterns and persistence levels of regimes do not necessarily improve with increased resolution