A zonal asymmetry in boreal winter surface temperature trend and its recent reversal over the Northern Hemisphere continents

A zonally asymmetric surface temperature trend has been observed in the boreal winter over the Northern Hemisphere continents from the late 1980s to the late 2000s. While the cooling trend was pronounced over central Eurasia, the warming trend was evident over Northeastern North America and Greenland. However, such trends were suddenly reversed in the late 2000s. The surface energy budget reveals that the downward longwave radiation due to the Arctic Oscillation (AO)-related temperature and moisture advection was mostly responsible for such trends. While the sensible heat flux also contributed to the temperature trend over central Eurasia, other terms play a minor role. This result suggests that a zonally asymmetric temperature trend in boreal winter and its recent reversal in the Northern Hemisphere continents are largely driven by the internal climate variability, particularly the AO-related thermodynamic and dynamic processes.