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

Abstract

Abstract This study employs the ERA5 and JRA55 monthly reanalysis datasets to examine the intraseasonal 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 impacts of the SCA pattern exhibit evident intraseasonal variations. Notably, the accumulated SAT anomalies over the region to the north of Tibetan Plateau (NP) due to the SCA pattern 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 to the east of Tibetan Plateau. 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, 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 gradients of both the air temperature and potential vorticity intensify, creating more favorable conditions for the vertical coupling between the upper and lower circulation anomalies associated with the SCA pattern. Consequently, the SCA pattern tends to persist, leading to significant SAT anomalies over both the NP and EC in February. These significant influences of the SCA pattern exhibit evident interdecadal variations.