Preceding Winter's ENSO Control on Summertime Atmospheric River Activity over the North Pacific

Recent studies showed that atmospheric rivers (ARs) are occasionally observed over the western, central and eastern North Pacific and are influenced by climate variability modes on different timescales. Especially sea surface temperature variability in the equatorial Pacific associated with ENSO modulates AR activity over the North Pacific on the interannual timescale. Previous studies mainly focused on the ENSO control on the landfalling AR over the western coast of the United States through its impact on the mid-latitude atmospheric circulation pattern. In contrast to the concurrent ENSO effect, delayed ENSO effect on the North Pacific AR through tropical trans-basin interactions is still unclear. This study reveals that the preceding winter's ENSO greatly modulates summertime AR activity over the North Pacific through the Indian Ocean-western Pacific Ocean Capacitor (IPOC) effects. Global atmospheric reanalysis and atmospheric general circulation model experiments consistently show anomalous AR activity over the North Pacific in the post El Niño summers associated with enhanced northwestern Pacific anticyclone and low-level southwesterly. The results of this study suggest that anomalous natural disaster risk related to summertime landfalling AR over East Asia is seasonally predictable based on the wintertime ENSO development.