Linkage between the NAO and Siberian high events on the intraseasonal timescale

Abstract

The Siberian high (SH) is a dominant component of the boreal winter circulation, and it significantly controls the climate of almost the entirety of continental Asia. Inspired by a case study of the “boss level” cold wave in 2016, intraseasonal SH events are classified into two types: positive-North Atlantic Oscillation (NAO)-related and negative-NAO-related SH events. Composite analysis shows that the SH events associated with the positive NAO often occur west of Eurasia and gradually amplify further westwards across Eurasia, which leads to warm Arctic-cold Eurasian surface temperature anomalies. The negative-NAO-related SH events often occur east of Eurasia and lead to almost all of the Eurasian negative surface temperature anomalies. Besides, the East Asian winter monsoon (EAWM) in the negative-NAO-related SH events presents stronger than that in the negative-NAO-related SH events. Before the peaks of the positive-NAO-related SH events, an upper tropospheric Rossby wave train originates from the North Atlantic, propagates across northern Eurasia, and interacts with preexisting cold surface anomalies over central Siberia, which is particularly crucial for the development and amplification of the positive-NAO-related SH events. In addition, the synoptic eddy-induced feedback originating from the North Pacific is the key factor in the development and amplification of the negative-NAO-related SH events.