Impacts of Autumnal Eurasian Snow Cover on Predominant Modes of Boreal Winter Surface Air Temperature Over Eurasia

In the present paper, the linkage between the predominant modes of boreal winter surface air temperature (SAT) anomalies over Eurasia and the preceding autumnal Eurasian snow cover is investigated for the period of 1979-2014. The first leading winter Eurasian SAT mode exhibits a strong signal over the region northward from 40 degrees N; in association with this SAT mode, a significant zonal dipole pattern in snow cover can be observed in the midlatitude Eurasia during November. Such anomalous November snow cover strengthens the wave activity flux upward propagating over the middle latitudes, which can change the stratospheric polar vortex thereafter. In the following winter, the anomalous polar vortex signal propagates downward to the surface and gives rise to the negative Arctic Oscillation-like structure. Consequently, this leads to the winter SAT anomalies occupying the area north of 40 degrees N. The second leading winter Eurasian SAT mode shows negative values northward from 60 degrees N as well as positive over the middle latitudes of Eurasia; in association with the second SAT mode, the significant anomalous snow cover appears to the east of the Ural Mountains during October. Such an anomalous snow signal can persist from October until the subsequent winter and produce a wave-like structure with a southeastward propagation from the Ural Mountains to the midlatitude Eurasia in the midtroposphere and upper troposphere, which results in the dipole anomalous temperatures lying in the middle to high latitudes of Eurasia. The preceding autumn snow cover signal is valuable for the prediction of the winter SAT over the Eurasian continent.