Interdecadal change of Eurasian snow, surface temperature, and atmospheric circulation in the late 1980s

Abstract

AbstractBoreal winter and spring snow cover extent and snow water equivalent over Eurasia experienced an obvious decrease in late 1980s. A concurrent surface warming is observed over the North Atlantic and Eurasia. The present study documents the relationship among the interdecadal changes in snow, surface air temperature, and wind and the plausible reason for this change. Analysis shows that the snow decrease contributes to the temperature increase only in some limited regions and that the surface warming is largely related to the change in atmospheric circulation. The effect of atmospheric circulation change on surface warming is manifested in wind‐induced heat advection and cloud‐radiation changes. The wind changes over the North Atlantic and Eurasia feature a wave train with an anomalous anticyclone over Europe and anomalous southerly winds over midlatitude east Europe and Asia. The anomalous southerly winds contribute to surface warming through advection of warmer air from lower latitudes. The anomalous anticyclone contributes to surface warming over Europe through anomalous warm advection by bringing warmer air from ocean and enhanced downward shortwave radiation by suppressing upward motion. The wave pattern appears to be connected to equatorial Atlantic warming. Warmer sea surface temperature (SST) in the equatorial Atlantic Ocean enhances convection and induces a lower level anomalous cyclone to the northwest of the SST warming. The role of equatorial North Atlantic SST increase in the formation of the wave train over Eurasia is supported by numerical experiments with an atmospheric general circulation model.