Article ID: 2021-058
An unprecedented cold wave swept through most parts of East Asia in January 2016, leading to record–breaking low temperatures and widespread snowstorms in many regions. Our analysis indicated that this East Asian cold wave was triggered by a series of consecutive extreme events in the Northern Hemisphere from late 2015 to early 2016. (1) On 28 December 2015, a severe cyclonic storm emerged in the North Atlantic, and a downstream blocking high formed in Europe through the downstream development process. The strong southerly jet stream between the storm and its downstream–blocking high steered the storm into the Arctic Circle, transported enormous warm and moist air masses, establishing warm conveyor belts, which led to an extraordinary Arctic warming event in late 2015; (2) This Arctic warming event in late 2015 resulted in a distinct Arctic dipole pattern resembling the negative phase of the Arctic Oscillation in early–mid-January 2016; and (3) The dipole pattern induced eastward propagation of the Rossby wave and led to the occupation of two downstream blocking highs in Urals and western North America. These two blocking highs, together with the low pressure between them, resulted in an inverted omega–shaped circulation pattern (IOCP) over the Siberia–North Pacific region. In addition, the IOCP distinctly modulated the meridional circulation cell along the East Asia–Siberia regions, which generated negative vorticity and anticyclonic advection to the Siberian region, ultimately intensifying the Siberian high. The IOCP and the associated enhanced Siberian high eventually induced the outbreak of a mega-cold wave in East Asia in January 21-25 2016.
