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

• Published in: Journal of geophysical research. Atmospheres 2018-09, Vol.123 (18), p.10,076-10,091
• Main Authors: Han, Shuangze, Sun, Jianqi
• Format: Article
• Language: English
• Subjects: Aerodynamics; Air temperature; Anomalies; Arctic Oscillation; Dipoles; Eurasian snow cover; Geophysics; Latitude; Mountains; Polar vortex; Snow; Snow cover; Stratosphere; Stratospheric polar vortexes; Stratospheric vortices; surface air temperature; Surface temperature; Surface-air temperature relationships; Troposphere; Upper troposphere; Vortices; wave activity flux; Wave propagation; Winter
• ISSN: 2169-897X; 2169-8996
• DOI: 10.1029/2018JD028443

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°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°N. The second leading winter Eurasian SAT mode shows negative values northward from 60°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. Key Points The midlatitude Eurasian zonal dipole pattern of November snow cover can exert an influence on the first mode of winter Eurasian surface air temperature The second mode of winter Eurasian surface air temperature has a close relationship with the October snow cover to the east of the Ural Mountains Snow cover‐related wave activity plays a crucial role in the connection between the autumn snow cover and winter surface air temperature over the Eurasian Continent