Multi-hazard Assessment of Extreme Hydrometeorological Events in Southeastern South America

Abstract

Southeastern South America is particularly vulnerable to extreme hydrometeorological events (EHEs). This study presents a multi-hazard analysis of long-term and short-term EHEs and their changes across southeastern South America for the 1961–1990 and 1991–2020 periods, using daily to monthly ERA5 data. Long-term EHEs are studied using the standardized precipitation index at 3- and 18-month timescales. Short-term EHEs are characterized by heatwaves, heavy precipitation, and flash droughts. Individual hazard components are derived by multiplying the frequency, duration, and intensity of the identified EHEs. The long-term and short-term EHE multi-hazard indices are formulated by aggregating these individual hazard components. Long-term multi-hazards prevail in the southwest and central west of the study region, including Argentina’s core crop region. A substantial water excess hazard hotspot is found in the southern areas, while the hotspot of seasonal to hydrological drought hazard is in northern and western areas. Short-term multi-hazards are more common in the north and central east, primarily impacting northeastern Argentina, southern Brazil, and southeastern Paraguay. In this hotspot region, heatwave hazard has increased by 30% in the last decades and flash drought and heavy precipitation frequencies are the highest. The current total multi-hazard, combining long-term and short-term multi-hazard indices, is higher and more widespread than between 1960 and 1990. Short-term hazards are more likely to co-occur, while long-term hazards tend to alternate. The study region is one of the most productive agricultural areas worldwide, so high EHE hazards can impact crop yields, threaten food security, and affect human well-being.