Science update: Influence of the propagation of stratospheric planetary waves on tropospheric blockings

K. Kodera and co-authors used case studies to investigate the relationship between stratospheric planetary wave reflection and blocking formation in the troposphere in a recent JGR paper. The enhanced upward propagation of a planetary-scale wave packet from the Eurasian sector, involving a Euro-Atlantic blocking, leads to a stratospheric sudden warming (SSW). Following the weakening of the stratospheric westerly jet due to polar warming, the stratospheric planetary wave packet then propagates downward over the American sector, inducing a ridge over the North Pacific as well as a trough over eastern Canada in the upper troposphere. The ridge promotes the formation of a Pacific blocking. This result explains why Pacific blockings tends to form after SSWs, and why they are associated with suppressed upward propagation of planetary waves. The full abstract can be found here.