Application of Land-Atmosphere Coupling Metrics to Better Understand Flash Drought Evolution and Intensification

Land-atmosphere coupling plays a critical role in hydroclimate extremes, however the larger focus has been on the impact of these interactions on the development of convective precipitation. Often neglected is the impact of land surface conditions on the development, intensification and propagation of dry extremes. Flash drought is a dry extreme characterized by rapid onset and intensification of drought conditions, which may or may not have been preceded by above or near normal rainfall. Recent research has focused on the detection of flash drought, but significant challenges remain regarding flash drought predictability. Further, such rapid onset of drought has vast societal implications and can threaten food and water security and yield political unrest in vulnerable locations. This study focused on the use of land-atmosphere coupling metrics to quantify the evolution of land-atmosphere interactions preceding and accompanying the onset of flash drought in the Southern Great Plains of North America. During periods of decreasing soil moisture,, Convective Triggering Potential and low-level Humidity Index (CTP/HI) standardized anomalies show strong covariability with soil moisture trends observed in Oklahoma. During 2011, drought conditions rapidly propagated eastward in Oklahoma, resulting in flash drought. The CTP/HI framework captured atmospheric conditions which suggested non-local modification of the low-level atmosphere by upstream drought which helped to enhance positive feedbacks that resulted in rapid propagation and intensification of drought in the eastern third of the state. During 2000, similar feedbacks were observed during July and August suggesting there is significant utility in the application of this framework to predicting the evolution of flash drought. This study will discuss the impacts of both non-local and local atmospheric and land surface conditions through on the evolution of flash drought cases through the lens of a modified CTP/HI framework to provide critical insight into the predictability of flash drought.