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This study investigates the characteristics of agricultural flash droughts (AFDs) and their impacts on critical growth periods of soybean and corn in southeastern South America (SESA). Using ERA5 data from 1960 to 2022, we examine AFD frequency, duration, intensity, trends, seasonality, life cycle, and the influence of land–atmosphere interactions. Historical crop data, spanning different time periods across SESA countries, are analyzed to assess how the spatiotemporal evolution and varying life cycles of AFDs affect crop yields. The highest AFD frequencies (3–8 events per decade) occur in the central portion of SESA. These rapidly intensifying events often evolve into seasonal droughts lasting 1.5–3 months. Although area-averaged AFD frequency shows no significant change in central SESA, positive trends are noticeable in southern Brazil and Uruguay. Towards the north of SESA, AFDs are less frequent, with 1–3 episodes per decade, although the frequency has significantly increased since 1970. AFDs tend to last over 3 months and reach higher intensity. Land–atmosphere feedback mechanisms are reflected in high positive vapor pressure deficit and temperature anomalies that exacerbate soil moisture deficits despite a relatively stable precipitation deficit, accelerating AFD intensification periods. AFDs typically impact smaller areas, while slow-evolving droughts affect larger regions. However, AFDs’ timing during the critical growth periods of the crops can lead to substantial yield losses. In central SESA, AFDs mainly occur between November and January, affecting both crops during their flowering and grain filling in December and January. In northern SESA, AFDs occur later, from February to April, primarily impacting second-season corn. The overall impact on crop yields depends on the duration, spatial extent, and intensity of the drought after its intensification.

This study evaluates the suitability of the European Space Agency Climate Change Initiative Combined Root-Zone Soil Moisture product (ESA CCI COM RZSM) for detecting agricultural flash droughts (AFDs) across southeastern South America (SESA) and assesses how satellite-based indicators capture their evolution and agricultural impacts. We identify AFDs using two complementary approaches based on RZSM percentiles and the Soil Water Deficit Index (SWDI). We compare AFD detection from ESA CCI COM RZSM against the fifth-generation European Centre for Medium-Range Weather Forecasts (ERA5) reanalysis RZSM over 1979–2022. To assess satellite-based representations of AFD evolution and impacts, we analyze satellite-derived RZSM, evapotranspiration (EVT), and three vegetation indicators—land surface water index, fraction of absorbed photosynthetically active radiation, and gross primary productivity—for two representative events. ESA CCI COM RZSM reproduces the main spatial patterns and seasonal cycles of AFD depicted by ERA5. However, it shows smoother temporal variability, delayed drying, and lower absolute RZSM, which may stem from its climatological rescaling and exponential filtering that propagates surface signals into deeper layers. Detection outcomes are highly sensitive to both methodology and dataset choice. The percentile-based approach tends to over-detect events in persistently wet or dry regimes. The SWDI-based method preserves regional hydroclimatic patterns and provides a more physically constrained representation of plant water stress. Satellite indicators capture the AFD progression, linking rapid RZSM depletion and reduced EVT to declines in vegetation productivity. The intensity and extent of impacts depend on antecedent SM and land cover, confirming the causal propagation of stress through the soil–plant–atmosphere system. Overall, the results demonstrate that ESA CCI COM RZSM, when combined with physically based indices and vegetation metrics, provides a robust, process-oriented foundation for AFD monitoring and early warning in SESA, where in situ observations are scarce.

This work examines the characteristics and prevalent life cycle of agricultural flash droughts globally. Using ERA5 data, the study introduces a flash drought indicator based on soil water availability. This approach integrates root-zone soil moisture and hydraulic soil properties, such as field capacity and wilting point, to couple the rapid soil moisture depletion and plant water stress. Our findings reveal that agricultural flash droughts present their higher frequency predominantly during the critical growth periods of crops. Notably, these droughts exhibit a similar life cycle regardless of the location or climatic regime. The primary cause of the rapid soil moisture depletion is the precipitation deficit, but evapotranspiration also plays a significant role. In an energy-limited environment, evapotranspiration rapidly increases before the onset and decreases rapidly during the intensification period as the system becomes water-limited. Upon concluding the intensification period, most crops experience water stress, diminishing their yields.

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.

Extreme hydrometeorological events (EHEs) pose significant risks to central-northeastern Argentina, requiring a nuanced understanding of subnational-level vulnerability and risk. This study integrates physical and socio-economic data to evaluate individual and multi-hazard risks across long-term and short-term time scales. Vulnerability is analyzed through exposure, sensitivity, and adaptive capacity. Risk is assessed as the interaction between EHE hazards and vulnerability. The analysis reveals a medium average vulnerability across the region, with marked spatial differences. Central Argentina—encompassing southern Santa Fe, eastern Córdoba, and northern Buenos Aires—shows medium vulnerability due to high exposure, counterbalanced by low sensitivity and high adaptive capacity. In contrast, northwest and central-western regions—including Formosa, eastern Salta, and eastern Santiago del Estero—exhibit high vulnerability driven by high sensitivity and low adaptive capacity despite low exposure. Heatwave risk is the highest and most widespread, particularly in northern Argentina. Risks from long-term dry and wet extreme precipitation display distinct regional patterns. Heavy precipitation risks are locally high in the northeast. Flash drought risk remains comparatively low across the region. The findings highlight that long-term multi-hazard risk is the most extensive and severe, while short-term multi-hazard risk is less widespread but dominated by heatwaves. Despite limitations, including uncertainties in input data and a constrained set of indicators, these results underscore the need for tailored adaptation strategies. Efforts should focus on reducing exposure in the south through improved infrastructure and agricultural practices and enhancing adaptive capacity in the north. Future research should explore compound risks and identify practical adaptation measures.