The Evaporative Stress Index as an Indictor for Flash Drought Across the United States Using Reanalysis Datasets

This study used the evaporative stress index (ESI) for flash drought identification across the United States applied to several reanalysis datasets including the National Centers for Environmental Protection North American Regional Reanalysis (NCEP NARR), the North American Land Data Assimilation System project phase 2 (NLDAS-2) community Noah land surface model, the interim ECMWF Re-Analysis (ERA-Interim), and the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2). Two criterions were used in the identification of flash drought including a “flash” component implemented to identify temporal periods of rapid intensification toward drought conditions based on decreasing ESI and preceded by below normal precipitation. Additionally, a criterion was also implemented to require the rapid intensification to end in drought. Combined, the change in mean normalized ESI pentads were used for the “flash” criterion while normalized ESI values were used to define drought conditions. Initial results using the NARR dataset spanning 1979-2016 quantified the spatial distribution of the frequency of flash drought events examined during the growing season (April through October) across CONUS along with the spatial evolution of flash drought development during specific events.