A 60 year minimum temperature record of 11 stations in inner Eurasia enabled the characterization of the Siberian High (SH) intensity. The decline in the SH intensity is observed in tandem with the positive mode of the Arctic Oscillation (AO), both increasing in recent years. The coldest 1968–1969 winter in the 60 year period corresponds with the lowest AO annual index value. Spatial correlation analyses indicate that enhanced cyclogenetic conditions over the eastern flank of the Icelandic Low (IL) are associated with a milder SH. Seasonal composite analyses of the circulation pattern during the coldest 1968–1969 winter are characterized by a retreat of the IL, allowing a westward expansion of the SH cold core. A robust methodology, assuring an adequate representation of extremely cold spells in both their extent and duration, was developed. This methodology yielded three exceptional events, the most severe one lasting 10 days and affecting all stations in the SH domain. Analysing this event on a fine temporal resolution enabled the detection of short-term synoptic scale processes, such as the polar air mass penetration, resulting in a mean minimum temperature of − 40 °C over the whole domain. This short-term polar air incursion and its termination featuring this spell, as modulated by the location of the IL, point at its important role in modifying the SH. Copyright © 2012 Royal Meteorological Society
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