East Asian atmospheric rivers are most hazardous in summer

This study investigates the hazard of East Asian Atmospheric Rivers (ARs) by applying the AR scale to AR catalog. When AR scale is categorized into five ranks from Category 1 (Cat1) to Category 5 (Cat5) by considering the duration and intensity of each AR event, with Cat5 having the most hazardous hydrological impact, Cat5 ARs are most frequently found in East Asian summer, along the northwestern boundary of the western North Pacific subtropical high. More frequent Cat5 ARs than Cat1 to Cat4 ARs are robustly found in eastern China, Korea, and western Japan, due to the slowly-varying monsoonal flow during the East Asian summer monsoon, which transports a large amount of moisture to the region. Since Cat5 ARs often lead to large event-total rainfall, it explains a close relationship of East Asian summer ARs to heavy rainfall events. This finding helps to better understand the potential hydrological impacts of ARs in East Asia.