부산대학교 도서관

The impacts of Arctic stratospheric polar vortex (SPV) on wintertime precipitation over the Northern Hemisphere are analyzed based on various datasets. Two groups of ensemble climate model experiments with the SPV nudged towards strong and weak states are performed to clarify stratospheric impacts on changes in precipitation. During weak SPV events, precipitation rates over the western and southeastern parts of North Pacific Ocean, the southern part of North Atlantic Ocean, and Southern Europe are larger, whereas the total precipitation rates over the central North Pacific, the northern part of North Atlantic and Northern Europe are smaller than those during strong SPV events. The SPV-induced changes in precipitation over the North Atlantic are stronger than those over the North Pacific. The convective (large-scale) precipitation changes play a major role in the total precipitation changes over the southern (northern) parts of middle latitudes associated with SPV changes. The tropospheric zonal wind deceleration around 60°N associated with weak SPV events is responsible for lower-tropospheric anomalous cyclonic flows over the two oceans at middle latitudes. The anomalous cyclonic flows lead to more large-scale precipitation in the southeastern parts of the oceans and less large-scale precipitation over Northern Europe and the central North Pacific during weak SPV events. The stratosphere–troposphere coupling over the North Atlantic is stronger than that over the North Pacific, leading to stronger large-scale precipitation responses over the former region. In addition, convective precipitation rates between 30 and 45°N are basically larger during weak SPV events than during strong SPV events. This is because more baroclinic waves associated with a southward shift of storm tracks during weak SPV events cause more heat exchanges between the lower latitudes and higher latitudes. Consequently, the upper tropospheric temperature and static ability between 30 and 45°N are reduced, leading to larger convective available potential energy and more convective precipitation during weak SPV events. [ABSTRACT FROM AUTHOR]