成層圏惑星規模波の下方伝播が北太平洋ブロッキングの形成に及ぼす影響

Abstract

Case studies are used to elucidate the relationship between stratospheric planetary wave reflection and blocking formation in the troposphere. It is found that due to modified stratospheric zonal mean flow associated with the occurrence of a stratospheric sudden warming (SSW), stratospheric planetary waves occasionally propagate 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 through interaction with synoptic transient eddies. This result explains why Pacific blockings tends to form after SSW.