Impacts of Background Conditions on the Evolutionary Disparities between Greenland and Euro-Atlantic Blocking

Abstract In this paper, we investigate the contrasting evolutionary behaviors and weather impacts of Greenland blocking and Euro-Atlantic blocking. The comprehensive analysis reveals that Greenland blocking is characterized by substantial amplitude, a prolonged lifespan, and notable westward movement, accompanied by significant warming over western Greenland and cooling over eastern North America and northern Europe. In contrast, Euro-Atlantic blocking remains quasi stationary, has a shorter duration, and features a smaller amplitude, resulting in only mild cooling over southern Europe. We elucidate the dynamic mechanism behind the evolution of these two types of blockings using the nonlinear multiscale interaction model of atmospheric blocking from the perspective of the meridional gradient of potential vorticity PV y . Here, atmospheric blocking is conceptualized as a wave packet comprising an envelope and a carrier wave. In contrast to Euro-Atlantic blocking, the wave packet envelope (WPE) of Greenland blocking displays a greater degree of nonlinearity and weaker high-order dispersion under weak background zonal wind and PV y conditions. This fosters the amplification and sustainability of the WPE, contributing to its large amplitude and extended lifespan. Greenland blocking also shows pronounced westward movement due to its large amplitude and the weak background PV y condition. The Euro-Atlantic blocking exhibits quasi-stationary and small-amplitude behaviors due to strong zonal wind and PV y conditions. Our findings indicate that the discrepancy in system dispersion, i.e., the relative velocity of the WPE and the carrier wave, between Greenland blocking and Euro-Atlantic blocking is negligible. The results emphasize that the variance in their evolutionary behaviors primarily stems from disparities in their WPEs.