Spatiotemporal variations of precipitation concentration influenced by large-scale climatic factors and potential links to flood-drought events across China 1958–2019

Understanding the irregularity of precipitation variations at both temporal and spatial scales is critical for assessing flood and drought risks. In this study, the statistical characteristics of precipitation variations in eight subregions were detected based on daily precipitation records from 798 meteorological sites during 1958–2019, and Long-term precipitation Concentration Index (LCI), Annual precipitation Concentration Index (ACI) and Seasonal precipitation concentration index (SPCI) values were used to analyse temporal heterogeneity of precipitation concentrations. Results showed that the LCI and ACI values were generally characterized by "high in southwest, low in Tibet, high in summer, and low in winter." Specifically, ACI presented significant increasing trends in 5 regions (Northeast, North, Tibetan Plateau, Western Northwest, and Eastern Northwest), insignificant increasing trends in 2 regions (Jianghuai and Southwest), and a significant decreasing trend in 1 region (South), indicating the potential of increased drought and flood risks. SPCI exhibited an increasing trend in the spring months in Northeast China (p < 0.01), and significant increasing trends in the Tibetan Plateau and Western Northwest China during autumn months (p < 0.05). Attribution analyses on 11 large-scale climatic factors showed that the El Nino-Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and Arctic Oscillation (AO) strongly influenced the precipitation concentration indices with distinct zonal characteristics. ENSO, which is the most significant factor affecting the precipitation concentrations, had the strongest positive effect in South China and coastal areas. Meanwhile, the NAO presented a notable negative influence on the ACI, while the AMO exhibited a positive impact in Northern China. Our work added to the body of evidence that the extreme rainfall events have been significantly increasing in the Tibetan Plateau, Western Northwest China, and Eastern Northwest China (p < 0.05), and that the north-western regions of China have been experiencing significant wetting trends. Furthermore, climate change would potentially lead to more extreme drought-flood events in the future.