Observational evidence differentiating Siberian High variability from the Ural-Siberian pattern

Most studies on atmospheric variability in the Northern Hemisphere (NH) have traditionally focused on the North Atlantic and North Pacific regions, due to the prominence of two main teleconnection patterns: the North Atlantic Oscillation (NAO) and the Pacific-North America (PNA). Despite being relatively overlooked compared to those two regions, Eurasia has gained an emerging interest due to its role in Arctic-mid latitude linkages, particularly in the so-called Warm Arctic-Cold Eurasia (WACE) pattern. The dynamics underlying this latter covariance seem to include an anticyclonic circulation over the Siberian coast whose identification has been ambiguous in literature. Here, we have diagnosed and characterized two distinct atmospheric variability modes, namely the Ural-Siberian (USib) pattern and the Siberian High (SH). The Ural-Siberian pattern, sometimes referred to as the Scandinavian (SCAND) pattern at upper levels, is identified as a regional mode of circulation variability maintained by transient-eddy activity and with a barotropic wave-like structure associated with Rossby wave propagation. Whereas Siberian High variability is mainly driven by radiative processes, i.e. the cooling effect of snow cover, and displays a baroclinic structure. While the signature on surface temperature of both atmospheric modes exhibits a dipole that can be identified as the WACE pattern, our results show clear spatial differences among them, being actually in quadrature (out-of-phase). The USib-related temperature signal shows positive anomalies over the Barents-Kara Seas associated with sea ice reduction and negative anomalies over the whole Eurasian continent related to northerly cold advection from the Arctic. In contrast, the SH signal depicts positive anomalies over northern Eurasia linked to warm advection from the south and negative anomalies around the core of the Siberian High due to an increase in snow cover. Further, we find that the vertical extension into the stratosphere of both patterns is distinct, with only the USib signal being consistent with an impact on the polar vortex.