The Downward Flux of Wave Energy in the Lower Troposphere Within the North Pacific Storm Track

Abstract Wave energy (WE) flux aligns with the direction of group velocity, in contrast to the conventional Eliassen‐Palm (EP) flux, which describes wave activity transfers. This study focuses on the climatological characteristics of WE flux within the North Pacific storm track using 6‐hourly output from the Japanese 55‐year Reanalysis (JRA‐55). In January, pronounced downward WE flux dominates the lower troposphere, while upward WE flux prevails in the upper troposphere, with a distinct divergence maximum around 500 hPa. The dynamical mechanism of this vertical structure is explained with the ascent‐descent configuration of air parcels in extratropical cyclones. Over the ocean, warm air plays a primary role in driving the WE flux, whereas over the continent, cold air motion becomes more influential. Two major baroclinic sources are identified near the Liao River basin and the eastern North Pacific, contributing to the growth of winter storms. Enhanced downward WE flux originating from 200 hPa above the Rocky Mountains is associated with the upper tropospheric advection of wave energy by the westerly jets. During midwinter, the upward WE flux in the upper troposphere over the central North Pacific is substantially suppressed, whereas the lower‐tropospheric downward WE flux does not exhibit a comparable minimum. These results highlight the importance of examining the vertical structure of WE flux for understanding storm‐track energetics and the maintenance of midlatitude winter circulation.