Science Daily November 23, 2020
Researchers at UCLA investigated the atmospheric river (AR) frequency trends over the Southern Hemisphere using three reanalyses and two Community Earth System Model (CESM) ensembles. Their results show that AR frequency has been increasing over the Southern Ocean and decreasing over lower latitudes in the past four decades and that ARs have been shifting poleward. While the observed trends are mostly driven by the poleward shift of the westerly jet, the experiments indicate anthropogenic forcing would result in positive AR frequency trends over the Southern Ocean due mostly to moisture changes. They conclude that the sea surface temperature variability characteristic of the negative phase of the Interdecadal Pacific Oscillation strongly suppresses the moisture‐driven trends while enhances the circulation‐induced trends over the Southern Ocean, thus bringing the simulated trends into closer agreement with the observed trends…read more. Open Access TECHNICAL ARTICLE