Influence of Eastern Tibetan Plateau Spring Snow Cover on North American Air Temperature and Its Interdecadal Change

Abstract

AbstractPrevious studies revealed the influence of the autumn–winter Tibetan Plateau snow cover on atmospheric circulation and climate in the North American region. The present study documents the relationship between the eastern Tibetan Plateau snow cover and the North American air temperature in spring and the associated physical processes using satellite-based snow cover, reanalysis atmospheric and surface variables, observation-based surface air temperature (SAT), and sea surface temperature (SST). A stable relationship is identified between the eastern Tibetan Plateau snow cover and the North American SAT in spring before the mid-2000s. Positive snow-cover anomalies over the eastern Tibetan Plateau induce cooling in the local atmospheric column. The atmospheric cooling stimulates a large-scale atmospheric wave pattern at the upper level that extends northeastward from the eastern Tibetan Plateau via northeast Asia and the North Pacific to North America. An anomalous high forms over North America, accompanied by anomalous descent. In the northwestern part, the horizontal advection by anomalous southerly winds along the west flank of anomalous anticyclone induces SAT increase. In the central part, the enhanced surface sensible heat flux following anomalous descent-induced downward shortwave radiation increase leads to SAT increase. The relationship between the eastern Tibetan Plateau snow cover and the North American SAT is weakened after the mid-2000s. The weakened relationship is attributed to an intensified impact of tropical central Pacific SST anomalies on the North American SAT variations through a Pacific–North America-like atmospheric circulation pattern, which overcomes the influence of the Tibetan Plateau snow-cover anomalies.