The El Niño Southe58rn Oscillation (ENSO) is a typical oscillation affecting climate change, and its stable periodicity, long-lasting effect, and predictable characteristics have become important indicators for regional climate prediction. In this study, we analyze the Standardized Precipitation Evapotranspiration Index (SPEI), the Niño3.4 index, the Southern Oscillation Index (SOI), and the Multivariate ENSO Index (MEI). Additionally, we explore the spatial and temporal distribution of the correlation coefficients between ENSO and SPEI and the time lag between ENSO events of varying intensities and droughts. The results reveal that the use of Nino3.4, MEI, and SOI produces differences in the occurrence time, end time, and intensity of ENSO events. Nino3.4 and MEI produce similar results for identifying ENSO events, and the Nino3.4 index accurately identifies and describes ENSO events with higher reliability. In China, the drought-sensitive areas vulnerable to ENSO events include southern China, the Jiangnan region, the middle and lower reaches of the Yangtze River, and the arid and semi-arid areas of northwestern China. Droughts in these areas correlate significantly with meteorological drought, and time-series correlations between ENSO events and droughts are significantly stronger in regions close to the ocean. Drought occurrence lags ENSO events: when using the Niño3.4 index to identify ENSO, droughts lag the strongest and weakest El Niño events by 0–12 months. However, when using the MEI as a criterion for ENSO, droughts lag the strongest and weakest El Niño events by 0–7 months. The time lag between the strongest ENSO event and drought is shorter than that for the weakest ENSO event, and droughts have a wider impact. The results of this study can provide a climate-change-compatible basis for drought monitoring and prediction.

China is rich in wind- and solar-energy resources. In recent years, under the auspices of the “double carbon target,” the government has significantly increased funding for the development of wind and solar resources. However, because wind and solar energy are intermittent and their spatial distribution is uneven, the profits obtained by the developers of wind- and solar-energy resources are unstable and relatively low. For this reason, we analyze in this article the spatiotemporal variations in wind and solar energy resources in China and the temporal complementarity of wind and solar energy by applying a Spearman correlation coefficient based on the Daily Value Dataset of China Surface Climate Data V3.0. Finally, we also strive to harmonize regions where wind and solar resources are less complementary by introducing hydro-energy resources. The results reveal that wind energy and solar energy resources in China undergo large interannual fluctuations and show significant spatial heterogeneity. At the same time, according to the complementarity of wind and solar resources, over half of China’s regions are suitable for the complementary development of resources. Further research shows that the introduction of hydro-energy resources makes it feasible to coordinate and complement the development of wind- and solar-energy resources in areas where the complementarity advantage is not significant. This has a significant effect on increasing the profit generated by the complementary development of two or more renewable resources.

Water security is crucial for the sustainable development of regional water resources. Here, we utilize the Driver-Pressure-State-Impact-Response (DPSIR) framework to construct an indicator system for assessing water security in the Lancang–Mekong River Basin (LMRB). This study also delves into the level of development in the coupling coordination between the economic and social systems and the water resources systems in the basin. The findings reveal that the overall water security situation in the LMRB is satisfactory, with three countries (China, Laos, and Vietnam) surpassing the “safe” threshold and three countries (Thailand, Cambodia, and Myanmar) “Basically safe”. However, water security issues persist, particularly in relation to water pollution and scarcity. Seasonal water shortages and water-related disasters arise due to uneven rainfall distribution throughout the year and inadequate regulating facilities such as wetlands and reservoirs. In addition, the overall coupling coordination level in the LMRB is low, ranging between 0.3 and 0.4, corresponding to a moderate imbalance level in the assessment criteria system. Specifically, Laos and China exhibit the highest coupling coordination level, with a degree of 0.36, whereas Thailand and Myanmar demonstrate the lowest level, with degrees of 0.33 and 0.31, respectively. Overall, our results offer a scientific foundation for the sustainable development of countries within the LMRB.