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Abstract. The term “flash drought” is frequently invoked to describe droughts thatdevelop rapidly over a relatively short timescale. Despite extensive andgrowing research on flash drought processes, predictability, and trends,there is still no standard quantitative definition that encompasses allflash drought characteristics and pathways. Instead, diverse definitionshave been proposed, supporting wide-ranging studies of flash drought butcreating the potential for confusion as to what the term means and how tocharacterize it. Use of different definitions might also lead to differentconclusions regarding flash drought frequency, predictability, and trendsunder climate change. In this study, we compared five previously publisheddefinitions, a newly proposed definition, and an operational satellite-baseddrought monitoring product to clarify conceptual differences and toinvestigate the sensitivity of flash drought inventories and trends to thechoice of definition. Our analyses indicate that the newly introduced SoilMoisture Volatility Index definition effectively captures flash droughtonset in both humid and semi-arid regions. Analyses also showed thatestimates of flash drought frequency, spatial distribution, and seasonalityvary across the contiguous United States depending upon which definition is used.Definitions differ in their representation of some of the largest and mostwidely studied flash droughts of recent years. Trend analysis indicates thatdefinitions that include air temperature show significant increases in flashdroughts over the past 40 years, but few trends are evident fordefinitions based on other surface conditions or fluxes. These resultsindicate that “flash drought” is a composite term that includes severaltypes of events and that clarity in definition is critical when monitoring,forecasting, or projecting the drought phenomenon. 

Abstract Wildfires are ecosystem‐level drivers of structure and function in many vegetated biomes. While numerous studies have emphasized the benefits of fire to ecosystems, large wildfires have also been associated with the loss of ecosystem services and shifts in vegetation abundance. The size and number of wildfires are increasing across a number of regions, and yet the outcomes of large wildfire on vegetation at large‐scales are still largely unknown. We introduce an exhaustive analysis of wildfire‐scale vegetation response to large wildfires across North America's grassland biome. We use 18 years of a newly released vegetation data set combined with 1,390 geospatial wildfire perimeters and drought data to detect large‐scale vegetation response among multiple vegetation functional groups. We found no evidence of persistent declines in vegetation driven by wildfire at the biome level. All vegetation functional groups exhibited relatively rapid recovery to pre wildfire ranges of variation across the Great Plains ecoregions, with the exception being a persistent decrease in the abundance of trees in the Northwestern Great Plains. Drought intensity magnified immediate vegetation response to wildfire. Persistent declines in vegetation cover were observed at the scale of single pixels (30 m), suggesting that these responses were localized and represent extreme cases within larger wildfires. Our findings echo over a century of research demonstrating a biome resilient to wildfire.