Contribution of Atmospheric Rivers to Precipitation and Precipitation Extremes in East Asia: Diagnosis with Moisture Flux Convergence

Atmospheric rivers (ARs), the long and narrow conveyors of intense moisture transport, have a non-negligible impact on hydrometeorological events over the extratropical regions. This study analyzes the climatology and interannual variability of ARs and their quantitative association with precipitation and precipitation extremes over East Asia (EA) during 1979–2019, based on calculations of not only moisture transport but also moisture flux convergence. It is found that the ARs over EA occur frequently in spring and summer, accounting for 25%–40% of seasonal precipitation and 60%–75% of extreme precipitation over EA. Increases in AR frequency are observed over EA during post-El Niño summers, meanwhile the AR-related anomalous moisture convergence is found leading to the increase of extreme precipitation. Specifically, increased ARs account for 70%–90% of total precipitation anomalies and up to 90% of extreme precipitation anomalies over the middle–lower reaches of the Yangtze River, and the anomalies of moisture flux convergence are caused mainly by changes in horizontal wind convergence rather than moisture advection during the post-El Niño summers.