Dominant modes and mechanisms of atmospheric rivers in East Asia

Atmospheric rivers (ARs), the long and narrow conveyors of intense moisture transport, are a unique mover of moisture from the low latitudes to the mid to high latitudes and have a considerable impact on hydrometeo-rological events (i.e., extreme precipitation). Using the top-hat by reconstruction (THR) algorithm and ERA5 reanalysis data, this study analyzes the climatological characteristics of ARs over East Asia (EA) in summer (June to August) during 1979-2020. According to the four leading modes of EOF analysis, ARs events occur mainly in the Yangtze River valley, the Huaihe River valley, and the coastal region of South China. The sea surface tem-perature anomalies (SSTAs) related to the first EOF mode (EOF1) show the warming of the central and eastern Pacific and Indian Oceans. The northward movement of the westerly jet stream maintains the western North Pacific subtropical high (WNPSH) and guides water vapor transport to China. EOF2 corresponds to the positive phase of EAP (East Asia-Pacific) pattern. SSTAs related to EOF2 show an El Nin similar to o recession-like pattern, which modulates precipitation over southern China through anticyclones over the western North Pacific. SSTAs related to EOF3 show a La Nin similar to a-like pattern, which regulates the precipitation in the Yangtze-Huaihe valley through upper-level convective heating on the north side of the WNPSH. For EOF4, the circulation system affecting ARs is dispersed, resulting in smaller scale ARs. ARs of EOF4 are associated with cyclones, mainly showing the char-acteristics of coastal landing ARs. These results can provide a new forecasting source for EA summer precipitation.

Automated summary

This study analyzes the climatological characteristics of atmospheric rivers (ARs) over East Asia during summer (June to August) from 1979 to 2020. The results reveal that ARs occur mainly in the Yangtze River valley, the Huaihe River valley, and the coastal region of South China. These findings have important implications for the prediction of summer precipitation in East Asia.