The Relationship between Winter Extremely Low Temperature Events in Mid-latitude Asia and Abnormal Warming over Barents-Kara Seas and Associated Mechanism

Based on the NCEP-DOE reanalysis data during 1979–2019, this paper investigated the relationship and correlation mechanisms between the frequency of winter extremely low temperature events in mid-latitude Asia and the abnormal warming over Barents and Kara Seas. The results show that the abnormal warming over Barents and Kara Seas usually corresponds to the enhancement of Siberian high and the frequent occurrence of extreme low temperatures in mid-latitude Asia. It is found that the positive geopotential height anomaly appears over Novaya Zemlya and Urals with the abnormal warming over the Barents and Kara Seas. Significant cold advection and sinking motion anomalies appear on the east and south sides of the positive geopotential height anomaly and the abnormal divergent flow appears near the ground, which makes Siberian high strengthening and extending to Southeast. The diagnosis using thermodynamic equations further indicates that cold advection anomaly caused by the northeast wind on the south side of the Siberian high pressure anomaly, the ascending motion anomaly caused by the easterly wind anomalies passing through the terrain, and the abnormal diabatic cooling caused by radiation, sensible heat, and latent heat result in an increase in the amplitude of the near-surface temperature’s seasonal cycle in mid-latitude Asia, which in turn favors the frequent occurrence of extreme low temperatures.