Understanding droughts under climate change in South America based on severity-duration-frequency curves and drought atlases

Droughts are among the most complex and costly natural disasters, with major impacts on environmental and socio-economic structures which are substantially influenced by anthropogenic factors. The continent of South America is particularly vulnerable and has experienced significant drought events over the past decade. The primary objective of this study is to enhance the understanding of droughts on this continent. Furthermore, it seeks to support the development of science-based decisions and strategies to mitigate the impacts of droughts on agriculture, water resources and wider socio-economic systems. To this end, Severity-Duration-Frequency (SDF) curves are developed using a copula-based approach, which offers a robust framework for assessing the likelihood and the impact of drought events. The analysis is carried out for the seven regions that describe the continent according to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR6) and based on ERA5 and CMIP6 data. Recurrence intervals of drought severity and duration are quantified for historical experiments (hist and histnat) and future climate scenarios (ssp245 and ssp585). These results are complemented by Drought Atlases for South America for different drought types. The results indicate that all analysed regions in South America will experience an increase in severity in the future, as anthropogenic emissions continue to rise. However, there are significant differences between the regions depending on the aggregation time, return period and experiment, particularly between the histnat and historical experiments. These findings can help inform policymakers designing region-specific drought policies, assist farmers in crop planning and irrigation, and guide water managers to optimise resource allocation and infrastructure planning, particularly in high-risk regions.