Making sense of flash drought: definitions, indicators, and where we go from here

The topic of “Flash Drought” has rapidly gained attention within the research and drought management communities within the last decade. In preparation for a recent workshop on Flash Drought, the National Integrated Drought Information System (NIDIS) prepared a literature review to synthesize the research to-date (as of August 2020) and to provide a basis for future research on the topic. Specifically, this review is focused on documenting the range of definitions of "flash drought" that have been proposed by the research community. The term first appeared in the peer-reviewed literature in 2002, and by 2020, has become an area of active research. Within that 18-year span, 19 papers have provided measurable, defining criteria used to distinguish a flash drought from other drought. Of these papers, 11 distinguish flash drought as a rapid-onset or rapid-intensification drought event while seven distinguish flash drought as a short-term or short-lived, yet severe, drought event, and one paper considers flash drought as both a short-lived and rapid-onset event. Currently, there is no universally accepted definition or criteria for “flash drought,” despite recent research that has called for the research community to adopt the principle of rapid-intensification of drought conditions. This topic was further explored at the NIDIS-sponsored Flash Drought Workshop on 1-3 December 2020, where additional perspectives were shared about the key characteristics of flash drought that should inform its definition.  We will provide a review of the literature-derived definitions as well as a brief overview of this additional discussion.