  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 e.g. 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.
