Monthly impact of the Scandinavian pattern on winter surface air temperature over Asia

Abstract

This study employs the ERA5 and JRA-55 monthly reanalysis datasets to examine the monthly impact of the Scandinavian (SCA) teleconnection pattern on the surface air temperature (SAT) over Asia in boreal winters from 1958 to 2021. We demonstrate that the monthly impacts of the SCA vary by month and region. Notably, the accumulated SAT anomalies over the region to the north of Tibetan Plateau (NP) due to the SCA tend to propagate southward to the eastern China (EC) during late winter, which is associated with the gradually intensifying westward gradient of the air temperature over the EC. Furthermore, both the November and January SCA patterns can significantly cause one-month-lagged SAT anomalies over the NP, albeit through different mechanisms. For the November SCA pattern, it induces significant snowfall anomalies over the NP and the associated snow cover anomalies can persist until December, facilitating the formation of local significant SAT anomalies via anomalous sensible heat flux. In contrast, from January to February, the background states for the air temperature in the lower troposphere and absolute vorticity in the upper troposphere change in such a way that creates a more favorable condition for the vertical coupling between the upper and lower circulation anomalies associated with the SCA pattern. Consequently, the SCA pattern tends to persist from January to February, leading to significant SAT anomalies over both the NP and EC in February.