Record-breaking Meiyu rainfall around Yangtze River in 2020 regulated by
the subseasonal phase transition of North Atlantic Oscillation
In 2020, the long-persisting Meiyu season around the Yangtze River (YR)
started in early-June and ended in mid–late-July. Its accumulated
precipitation amount broke the record since 1961. We showed that the
sequential warm and cold Meiyu front regulated by the North Atlantic
Oscillation was responsible for this record-breaking Meiyu rainfall.
From 11 to 25 June with the positive NAO, the interaction between South
Asian High (SAH) and western Pacific subtropical high maintained a warm
front to strengthen the rainband north of YR. Afterward, the coupling
between SAH and mid-latitude Mongolian Cyclone induced a cold front,
which retreated the rainband to the south of YR from 30 June to 13 July
with the negative NAO. Although the ECMWF S2S successfully predicted the
warm-front-related Meiyu rainband, it failed to forecast the Meiyu
rainband in the cold-front period, suggesting a great challenge of the
S2S forecast on Meiyu rainfall.