Flash Drought Climatology: A Local to Global Analysis

Abstract:

Flash drought is a critical subseasonal phenomenon whereby rapid drought intensification occurs over a limited temporal period (weeks to months). Given the rapid nature of these events, moisture stress on the environment can arise with limited warning and lead to devastating impacts on agricultural yields. In addition to vegetative stress, flash droughts have the potential to initiate cascading hydrometeorological events (e.g., heatwaves, long-term drought) and societal impacts (e.g., reduced short-term water resources, wildfires). As the scientific community continues to explore flash drought detection, monitoring, and prediction, it remains essential to understand which regions have an enhanced risk for flash drought development.

An overview of climatological flash drought occurrence will be provided for the United States and across the globe. Flash droughts were identified using the standardized evaporative stress ratio (SESR; the ratio of evapotranspiration and potential evapotranspiration) in conjunction with a methodology that places an emphasis on 1) the rapid rate of intensification toward drought and 2) environmental impacts resulting from flash drought. SESR and the methodology were applied to multiple reanalysis datasets to determine climatological hot spots in flash drought occurrence. For the United States, flash drought occurrence is more frequent across the central U.S., including large portions of the Great Plains and Midwest. Globally, flash drought risk is enhanced in areas with notable land-atmosphere coupling, localized monsoon regions, and locations with large-scale agricultural production. From an intra-annual perspective, flash drought frequency in northern latitude regions was generally highest during the Northern Hemisphere summer, while southern latitude regions had their highest flash drought frequency in the Southern Hemisphere summer. Lastly, several flash drought hot spots and extensive agricultural regions across the globe exhibited statistically significant changes in flash drought spatial coverage over the time period of study (1980-2015).