Reproducibility of atmospheric circulation regimes over the winter Northern Hemisphere by the INMCM5 Earth system model

Abstract Weather regimes, i.e., recurrent and persistent large-scale structures of atmospheric circulation, is the dominant manifestation of the low-frequency variability of the mid-latitude atmosphere on subseasonal time scales. Here we suggest a method for studying reproducibility of these structures in the Earth system model simulations, including ensemble experiments. The method is based on the identification of the metastable structures in the state space of the system by means of the hidden Markov model approach. Constructing a Markov evolution operator from data allows us to detect statistically significant communities of the system states with abnormally long lifetimes. Capabilities of the approach are demonstrated on the analysis of data obtained in historical and preindustrial experiments with INMCM Earth system model. The set of the detected regimes is presented and compared with the regimes extracted from reanalysis data. Structures of atmospheric anomalies of geopotential heights, surface air temperatures and precipitations in the obtained regimes are presented.