Development and Characterization of U.S. Drought Monitor Based Drought Events

In general, drought is defined as a moisture deficit within the hydrological cycle that when persistent over time has far-reaching impacts on agriculture, water resources, and human health in addition to environmental degradation. One of the main challenges of monitoring and evaluating the severity of drought is the lack of a unified drought definition. In the literature, drought events are often defined using a single hydrological metric (indices based on precipitation, soil moisture, evaporation, streamflow, etc.) rather than incorporating conditions across the hydrological cycle. The U.S. Drought Monitor (USDM) was established in the early 2000s to provide weekly updates of National drought conditions from datasets that transect the hydrological cycle. With over 19 years of data, this dataset provides an opportunity define unique drought events and evaluate their frequency of occurrence, peak intensity, rapid intensification, persistence, and seasonality of drought onset across the U.S. Results showed that while drought events were more frequent across central and southeastern U.S. they were more persistent (longer lasting) over the western U.S. The value of a USDM based drought definition is that it incorporates data across the hydrological cycle (rather than a single measure), making it an ideal definition of drought that can be used across researcher, decision-maker, and other relevant communities. This is particularly important when evaluating the utility of specific hydrological indicators, such as soil moisture and or precipitation, for the detection of drought onset, intensification, and amelioration. A historical drought event dataset also provides an opportunity to develop and evaluate drought mitigation strategies.