Climatology and Interannual Variability of Atmospheric Rivers and Their Impact on Precipitation over East Asia

Atmospheric rivers (ARs), as long and narrow conveyors of intense moisture transport, have a non-negligible impact on hydrometeorological events over the extratropical regions. This study analyses climatology and interannual variability of ARs and their influence on precipitation over East Asia (EA) during 1979–2019. The ARs over EA occur more frequently in spring and summer than in autumn and winter. ARs account for 25%–40% of accumulated precipitation and 60%–75% of extreme precipitation over EA in spring, summer, and winter. AR-produced water vapor convergence is favorable to in-situ extreme precipitation over EA. We further investigate the relative importance of wind convergence and moisture advection to extreme precipitation. It is suggested that AR-produced water vapor convergence is dominated by horizontal wind convergence. During post-El Nino summers, increases of AR frequency are seen over EA. Positive anomalies of ARs account for 70%–90% of total precipitation anomalies, especially up to 90% of extreme precipitation anomalies over the middle and lower reaches of the Yangtze River basin. Anomalous AR-related moisture convergence leads to the increase of extreme precipitation. The convergence anomalies of moisture transport are decided by changes in wind convergence during post-El Nino summers.