Global distribution, trends, and drivers of flash drought occurrence


Flash drought is characterized by a period of rapid drought intensification with impacts on agriculture, water resources, ecosystems, and the human environment. Addressing these challenges requires a fundamental understanding of flash drought occurrence. This study identifies global hotspots for flash drought from 1980–2015 via anomalies in evaporative stress and the standardized evaporative stress ratio. Flash drought hotspots exist over Brazil, the Sahel, the Great Rift Valley, and India, with notable local hotspots over the central United States, southwestern Russia, and northeastern China. Six of the fifteen study regions experienced a statistically significant increase in flash drought during 1980–2015. In contrast, three study regions witnessed a significant decline in flash drought frequency. Finally, the results illustrate that multiple pathways of research are needed to further our understanding of the regional drivers of flash drought and the complex interactions between flash drought and socioeconomic impacts. Introduction

Flash drought is a critical sub-seasonal phenomenon that exhibits multifaceted challenges to agriculture, the economy, and society 1 . Given the rapid land-surface desiccation associated with flash drought, the agricultural sector can be devastated and experience substantial economic damage due to lower crop yields and curtailed livestock production 1 , 2 , 3 , 4 . Rapid drought intensification can severely impact ecosystems via excessive evaporative stress on the environment 5 , 6 , 7 , 8 , 9 , 10 and contribute to compound extreme events with cascading impacts including an increased risk for wildfire development, depletion of water resources, reduction of air quality, and decreased food security 11 , 12 , 13 , 14 , 15 , 16 .

With a wide range of impacts associated with flash drought and challenges related to its sub-seasonal prediction 17 , 18 , a critical goal within the scientific community is to advance knowledge of flash drought events. As such, research has been undertaken to improve the detection, evaluation, and monitoring of flash drought, including sub-surface analysis with soil moisture 19 , atmospheric evaporative demand 8 , 20 , evaporative stress via evapotranspiration (ET) and potential evapotranspiration (PET 6 , 7 , 9 ), and impact-based approaches 21 . In addition, rapid drought intensification has been identified across the United States 3 , 6 , 22 , Brazil 23 , southern Africa 24 , Spain 25 , western Russia 15 , and Australia 10 . A critical next step that builds upon these regional studies is to quantify the global distribution of flash drought, the seasonal frequency of flash drought, the trends in the occurrence of rapid intensification toward drought, and the drivers of flash drought development.

While recent progress in flash drought research has been accomplished via case studies and regional analyses, a key scientific question remains: What global regions are the most susceptible to flash drought occurrence? To address this question, the spatial distribution of flash drought events was identified via four global reanalysis data sets for the period spanning 1980–2015. The results presented here reveal 1 the regions with the strongest, reanalysis-based consensus for […]

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