Drought-flood abrupt alternation events and their impacts in China

Drought-flood abrupt alternation (DFAA), characterized by a period of persistent drought followed by sudden heavy precipitation at a certain level, has significant impacts on ecosystems and socioeconomic environment. As previous studies mainly focused on the monthly scale and regional scale, our study proposed a multi-indicator daily-scale method for identifying the DFAA occurrence. Then we applied the method on exploring the DFAA events over China from 1961 to 2018. The results show that: i) The DFAA events mainly occurred in the center and southeast of China. ii) The spatial coverage has a statistically significant (p < 0.05) increasing trend over China, of 0.355 %/decade. iii) The occurrence and spatial coverage of DFAA events increased by decades, and were mainly concentrated in summer (around 85%). Meanwhile, we conducted field experiments in typical area. The measurements revealed that DFAA events increased the soil nitrogen and phosphorus pollution in surface water.