Quantifying climate model representation of the wintertime Euro-Atlantic circulation using geopotential-jet regimes

Abstract. Even the most advanced climate models struggle to reproduce observed wintertime circulation of atmosphere over North Atlantic and western Europe. During winter, large-scale motions this particularly challenging region are dominated by eddy-driven highly non-linear flows, whose low-frequency variability is often studied from perspective regimes – a small number qualitatively distinct atmospheric states. Poor representation associated with persistent blocking events, or variations in jet latitude, degrades ability correctly simulate extreme events. In paper we leverage recently developed hybrid approach which combines both geopotential height data assess 8400 years historical simulations drawn Coupled Model Intercomparison Project (CMIP) experiments, CMIP5, CMIP6, HighResMIP. We show that these geopotential-jet suited analysis data, considerable reductions sampling compared classical regime approaches. find CMIP6 has considerably improved spatial structure, more trimodal jet, relative but it still struggles under-persistent too little European when reanalysis. Reduced persistence can be understood, at least part, as result jets fast eddy feedbacks on stream weak structural errors do not noticeably improve higher-resolution models.