Opposite Interdecadal Trends of Summer Atmospheric Rivers over East Asia
and Western North Pacific in Recent Decades
Abstract
The summer atmospheric river (AR) frequency over East Asia and Western
North Pacific (EA-WNP) is investigated by multiple AR detection
algorithms based on the Atmospheric River Tracking Method
Intercomparison Project (ARTMIP) Tier2 reanalysis dataset. The results
show that AR frequency during the recent four decades experienced
opposite interdecadal shifts, greatly contributing to the interdecadal
equatorward trends of EA ARs and poleward trends of WNP ARs with a
boundary around 135°E. The opposite variations are mainly influenced by
a zonal dipole of integrated water vapor transport with cyclonic and
anticyclonic anomalies centered over Taiwan and the ocean to the
southeast of Japan, respectively. A major impact of the Pacific Decadal
Oscillation and a reinforcement effect due to a zonal wave train from
the North Atlantic jointly modulate the pattern. Considering ARs may
curve their pathway over EA-WNP, the algorithms based on historical AR
shapes should be cautiously used during AR detection.