Atmospheric circulation regime causing winter temperature whiplash events in North China

Temperature whiplash events, which are characterized by a rapid transition between persistent and extreme warm and cold conditions, usually damage natural systems and human communities and can even have catastrophic impacts. To more deeply understand the severe winter temperature whiplash events in North China, in this study, the atmospheric circulation regime that is primarily responsible for such events is investigated based on Japanese 55-year reanalysis data. The results show that the drastic temperature shifts during winter temperature whiplash events are closely correlated with the southeastward propagation of the dipolar anomalous temperature in the middle and lower troposphere over the Eurasian continent. The dipolar structure of the temperature signals features an initial cold anomaly over the West Siberian Plain and a warm anomaly over East Asia during negative (extremely warm to extremely cold) events and the opposite pattern during positive (extremely cold to extremely warm) events. This dipolar temperature anomaly is tightly coupled with the southeastward development of an upper-level wave-like anomalous circulation pattern over the Eurasian continent, which is associated with a Rossby wave originating near the Kara Sea during negative events and in northern Europe during positive events. Based on the calculation of the temperature budget, the drastic temperature drop during negative events is mainly dominated by anomalous meridional temperature advection, and adiabatic heating due to vertical motion is negligible. In contrast, adiabatic heating due to sinking plays a dominant role in the drastic temperature increase during positive events, while anomalous meridional temperature advection also makes a substantial contribution to the temperature increase.