Spatiotemporal Variability of Precipitation Concentration and Its Rate of Contribution to Meteorological Drought in Mainland China

Climate change has increased the frequency and intensity of hydrometeorological extreme events all over the world. Uneven precipitation patterns, both spatially and temporally, have triggered more frequent and devastating droughts and floods. To assess these variations and their impact on drought, this study analyzed grid-based meteorological data to calculate the concentration index (CI) and precipitation concentration index (PCI) in mainland China from 1961 to 2022. Monthly temperature and precipitation data were also used to derive the standardized precipitation evapotranspiration index (SPEI) using Hargreaves equation. The nonparametric Pettitt’s test was investigated to identify the turn and change points for CI and PCI across mainland China. Sen’s slope from the Mann–Kendall method calculated trends before and after these turn points (YTPs) and the overall drought trend. A structural equation model (SEM) provided qualitative and quantitative evaluations of how the annual PCI contributes to annual drought severity. High CI values are predominantly observed in the southern and northeastern parts of the Pearl River Basin (PRB), as well as in the central areas of the Yellow River Basin (YRB), Haihe River Basin (HaRB), and Huaihe River Basin (HuRB). The SEM approach enables the study to disentangle and quantify the direct and indirect contributions of precipitation concentration to drought, providing a deeper understanding of how uneven rainfall distribution influences annual drought severity across different regions. Finally, the study provides region-specific findings, identifying key areas where PCI is the dominant factor influencing drought variability, with contribution rates exceeding 50% in over half of mainland China. These insights not only enhance the understanding of the linkage between precipitation distribution and drought but also offer actionable guidance for water resource management and drought mitigation strategies.