In recent years, East Asia has experienced a significant increase in the frequency and intensity of heavy rainfall events. Such events are often driven by strong moisture transport in the form of atmospheric rivers (ARs). While previous studies investigated the association of ARs with rainfall events (i.e., rainfall-centric), our understanding of the physical characteristics of ARs causing heavy rainfall (i.e., AR-centric) remained unclear. Previous AR-centric studies in the region have primarily been event-based, making it difficult to generalize the physical characteristics of ARs responsible for heavy rainfall. In this study, we examined the characteristics of ARs—specifically their sequence and duration—from the AR perspective, using data from 1988 to 2023. We first calculated Integrated Water Vapor Transport (IVT) based on ERA5 reanalysis and extracted the associated precipitation from the Radar-AMeDAS. ARs were defined by applying a 24-hour moving average to IVT and comparing it to a grid-specific threshold. Consecutive ARs separated by intervals of less than 24 hours were grouped into a single "AR event." For each event, we quantified the number of ARs and event duration, and analyzed their relationships with precipitation and IVT. Our results showed that the number of ARs within an event has a stronger influence on total precipitation than IVT magnitude alone. Moreover, multi-AR events are causing higher precipitation in regions experiencing higher frequency of multi-AR events. These findings underscore the importance of understanding sequenced AR activity as a distinct mechanism for generating extreme precipitation, which will be further investigated in future research.
TADAKI et al. (2026) studied this question.