Spatiotemporal variations in extreme precipitation on the middle and lower reaches of the Yangtze River Basin (1970-2018)

Extreme precipitation events are likely occur more frequently and lead to casualties and socio-economic losses as global warming intensifies. Therefore, exploring the characteristics of extreme precipitation events is essential. Based on meteorological station data from the middle and lower reaches of the Yangtze River Basin (MLYRB) from 1970 to 2018, we analyzed the spatiotemporal distributions of 11 extreme precipitation indices and considered the correlation between altitude and large-scale atmospheric circulation with extreme precipitation. To this end, we employed Sen's trend analysis, rescaled range analysis, the Mann-Kendall test, and continuous wavelet transform. The results indicate that on this spatial scale, extreme precipitation indices in the northwestern region of the MLYRB have mainly decreased, but they have increased along the eastern coastal region. From the perspective of the entire region, Hurst values of extreme precipitation indices are >0.5. Areas with consistent increases are mainly concentrated in the central region, while those with consistent decreases are mainly scattered in the northern and southern regions. Abrupt change in extreme precipitation indices mostly occurred in the 1980s and 1990s. The periodic oscillations of most indices tend toward high time-frequency scales (2.3 years or less). Consecutive wet days increased with increasing altitude; other indices changed similarly with increasing altitude, first increasing then decreasing before increasing again. Additionally, we found significant resonance periods between the extreme precipitation indices and the atmospheric circulation index, however, there were obvious differences in time domains.