Spatiotemporal variations of precipitation concentration and their potential links to drought in mainland China

Climate warming triggers increased frequency and intensity of extreme climate events, and due to disequilibrium precipitation at spatial and temporal scales, droughts or floods may occur frequently. Therefore, it is necessary to assess spatiotemporal variation of precipitation concentration and its potential impact on drought. The study calculated the Concentration Index (CI) and Precipitation Concentration Index (PCI) of 780 stations during 1961-2016 in mainland China, and monthly temperature and precipitation data were adapted to calculate the Standardized Precipitation Evapotranspiration Index (SPEI). Changepoint method was used to determine the turn and change points of CI and PCI, and Sen's slope method was used to calculate the trend before and after the year of turn points (YTPs) and the overall trend of drought was also analyzed. The Pearson correlation method was employed to evaluate the correlation between CI/PCI and SPEI to explore potential influence of precipitation concentration on drought from qualitative and quantitative perspectives. The results demonstrate that the annual CI ranges from 0.56 to 0.75, and the 25% rainiest days account for 68.35%-85.92% of total precipitation. The summer CI was the largest and the winter CI was the smallest among all seasons. 9.74% and 9.62% of stations were observed with change points for annual CI and PCI, respectively. Meanwhile, 80.13% and 69.36% of stations for annual CI and PCI showed a decreasing trend, respectively, and 73.21% of stations exhibited a trend of drought. Annual SPEI was positively correlated with CI and PCI, accounting for 88.59% and 70.77% of stations in mainland China, respectively, indicating that the variation of drought was more sensitive to CI than to PCI. The results can provide a basis for decision-making in water resources and drought risk management in China.