Origins of multi-decadal variability in sudden stratospheric warmings

Abstract. Sudden stratospheric warmings (SSWs) are major disruptions of the Northern Hemisphere (NH) polar vortex and occur on average approximately six times per decade in observation-based records. However, within these records, intervals significantly higher lower SSW rates observed, suggesting possibility low-frequency variations event occurrence. A better understanding factors that influence this decadal variability may help to improve predictability NH midlatitude surface climate, through stratosphere–troposphere coupling. In work, multi-decadal events is examined a 1000-year pre-industrial simulation coupled global climate model. Using wavelet spectral decomposition method, we show hiatus (intervals or more with no SSWs) consecutive (extended at least one each year) vary timescales periods between 60 90 years. Signals present for 450 years simulation. We investigate possible source long-term signals find direct impact tropical sea temperatures, as well associated Aleutian Low, can account only small portion variability. Instead, amplitude quasi-biennial oscillation (QBO). The QBO consistent well-known Holton–Tan relationship, extended particularly strong, deep westerly phases. results support recent studies have highlighted role vertical coherence when considering coupling QBO, tropospheric circulation.