Was the Record-Breaking Mei-yu of 2020 Enhanced by Regional Climate Change?

In 2020, the middle and lower reaches of the Yangtze River (MLYR; 28°–33°N, 110°–121°E) in China suffered an unexpected long-persisting mei-yu season, and both the duration and rainfall amount reached the highest record since 1961 (Wei et al. 2020). In particular, the average cumulative precipitation for the period of 1 June to 31 July exceeded +750 mm with a maximum value of 1720 mm, and the precipitation anomaly reached +350 mm (Fig. 1a), which was about 88% more than 1980–2010 climatology in this region (Fig. 1b). The corresponding extreme precipitation caused severe flooding over the MLYR region, affecting 63.46 million people and resulting in a direct economic loss of over 178.96 billion Yuan (https://www.chinanews.com/ sh/2020/08-14/9264482.shtml). This super mei-yu was primarily driven by the enhanced upward movement and moisture flux (Fig. 1c). They were caused by the abnormal East Asian westerly jet in the upper level and the southwesterly jet in the lower level, which were associated with abnormal position and intensity of the western Pacific subtropical high (Ding et al. 2021). These circulation anomalies coincided with the North Atlantic Oscillation (NAO; Liu et al. 2020), North Atlantic SST anomaly (Zheng and Wang 2021), the strong preceding Indian Ocean dipole (IOD; Takaya et al. 2020; Z.-Q. Zhou et al. 2021), a rap