A Climatology of Single-Day Rapid Drought Cessation Events Across the Southwestern United States

Authors: Emily P. Harris*, University of West Florida, Department of Earth and Environmental Sciences, Jason T. Ortegren, University of West Florida, Department of Earth and Environmental Sciences
Topics: Climatology and Meteorology, Arid Regions, Earth Science
Keywords: Southwest United States, drought, climatology, rapid drought cessation events
Session Type: Poster
Day: 4/4/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded


Drought is a common and important component of the hydroclimatology of the southwestern USA. Much research has focused on causes, spatial and temporal variability, and the economic and ecological impacts of drought in the Southwest. However, less attention has been paid to drought termination in the region, especially Rapid Drought Cessation Events (RDCEs), which in some regions can be responsible for ending up to 73% of warm-season droughts. Here, we identified the “Southwest” drought region using Principal Components Analysis (PCA) of the annual average Palmer Drought Severity Index (PDSI) for all NOAA state climate divisions in the U.S.A. For the Southwest region, 9,256 droughts occurred during 1895-2017. 575 (6.2%) of these droughts ended abruptly (in the course of one month’s time). Furthermore, 54 (0.6%) of those RDCEs occurred in a single day. The majority of RDCEs, and single-day RDCEs, occurred in fall, with a secondary maximum in winter. Droughts of short (<6 months) and long (>83 months) duration were ended by single-day RDCEs. Similarly, RDCEs were able to end droughts of varying severity, including extreme (e.g. -5.68 PDSI recorded in November 1951) and moderate (e.g. -2.01 PDSI recorded in April 1929) droughts. The frequency of single-day RDCE increased from the first to the second half of the period of study, with the greatest increase in the winter season and most occurring in Arizona. Analyses are in progress to identify the storm type responsible for every occurrence of RDCE and describe the spatiotemporal properties of RDCE associated with each storm type.

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