Links between atmospheric blocking and North American winter cold spells in two generations of Canadian Earth System Model large ensembles

Abstract Due to the significant negative consequences of winter cold extremes, there is need better understand and simulate mechanisms driving their occurrence. The impact atmospheric blocking on spells over North America investigated using ERA-Interim NCEP-DOE-R2 reanalyses for 1981–2010. Initial-condition large-ensembles two generations Canadian Earth System Models (CanESM5 its predecessor, CanESM2) are evaluated in terms ability represent blocking-cold spell linkage associated internal-variability. reanalysis datasets show that 72 58% southern northern coincide with occurring high-latitude Pacific-North America. Compared reanalyses, CanESM2 CanESM5 ensembles underestimate by 19.9 14.3% events coincident blocking, due under-representation frequency Pacific (− 47.1 − 29.0%), whereas biases relatively small (6.6 4.7%). In regions statistically above-normal relative climatology lie east and/or south flanks events, those below-normal along core or surrounding blocking. reproduce observed America, despite underestimating magnitude frequency. also physical drivers underpin linkage. Spatial agreement found simulated patterns temperature advection surface heat flux forcing anomalies during events. While shows an improved representation CanESM2, both yield similar results