Assessing the Evolution of Soil Moisture and Vegetation Conditions during a Flash Drought—Flash Recovery Sequence over the South-Central United States

This study examines the evolution of atmospheric, soil moisture, and vegetation conditions during an unusual flash drought, flash recovery sequence that occurred across the south-central U.S. in 2015. This event was characterized by a period of rapid drought intensification (flash drought) during late summer that was terminated by heavy rainfall at the end of October that eliminated drought conditions during a two-week period (flash recovery). A detailed analysis of the event was performed for select regions. Though the analysis revealed a similar progression of cascading effects in each region, characteristics of the flash drought such as its onset time, rate of intensification, and vegetation impacts differed in each region due to variations in the antecedent conditions and the atmospheric anomalies during its growth. Overall, flash drought signals initially appeared in the near-surface soil moisture and gross primary productivity, followed closely by reductions in evapotranspiration. Total column soil moisture deficits took longer to develop, especially in the western part of the region where heavy rainfall during the spring and early summer led to large moisture surpluses. Large differences were noted in how land surface models in the North American Land Data Assimilation System depicted the evolution of the flash drought, with one model consistently depicting better conditions than the other models. Much smaller differences occurred during the flash recovery period. This study illustrates the need to use multiple datasets to track the evolution of a flash drought.