Editorial Type:
Article
Article Type:
Research Article

Using Temporal Changes in Drought Indices to Generate Probabilistic Drought Intensification Forecasts

Jason A. Otkin Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison, Madison, Wisconsin

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Martha C. Anderson Hydrology and Remote Sensing Laboratory, Agricultural Research Services, U.S. Department of Agriculture, Beltsville, Maryland

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Christopher Hain Earth System Interdisciplinary Center, University of Maryland, College Park, College Park, Maryland

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Mark Svoboda National Drought Mitigation Center, University of Nebraska–Lincoln, Lincoln, Nebraska

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Print Publication:
01 Feb 2015
DOI:
https://doi.org/10.1175/JHM-D-14-0064.1
Page(s):
88–105
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Abstract

In this study, the potential utility of using rapid temporal changes in drought indices to provide early warning of an elevated risk for drought development over subseasonal time scales is assessed. Standardized change anomalies were computed each week during the 2000–13 growing seasons for drought indices depicting anomalies in evapotranspiration, precipitation, and soil moisture. A rapid change index (RCI) that encapsulates the accumulated magnitude of rapid changes in the weekly anomalies was computed each week for each drought index, and then a simple statistical method was used to convert the RCI values into drought intensification probabilities depicting the likelihood that drought severity as analyzed by the U.S. Drought Monitor (USDM) would worsen in subsequent weeks. Local and regional case study analyses revealed that elevated drought intensification probabilities often occur several weeks prior to changes in the USDM and in topsoil moisture and crop condition datasets compiled by the National Agricultural Statistics Service. Statistical analyses showed that the RCI-derived probabilities are most reliable and skillful over the central and eastern United States in regions most susceptible to rapid drought development. Taken together, these results suggest that tools used to identify areas experiencing rapid changes in drought indices may be useful components of future drought early warning systems.

Corresponding author address: Jason A. Otkin, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison, 1225 W. Dayton St., Madison, WI 53706. E-mail: jason.otkin@ssec.wisc.edu

Abstract

In this study, the potential utility of using rapid temporal changes in drought indices to provide early warning of an elevated risk for drought development over subseasonal time scales is assessed. Standardized change anomalies were computed each week during the 2000–13 growing seasons for drought indices depicting anomalies in evapotranspiration, precipitation, and soil moisture. A rapid change index (RCI) that encapsulates the accumulated magnitude of rapid changes in the weekly anomalies was computed each week for each drought index, and then a simple statistical method was used to convert the RCI values into drought intensification probabilities depicting the likelihood that drought severity as analyzed by the U.S. Drought Monitor (USDM) would worsen in subsequent weeks. Local and regional case study analyses revealed that elevated drought intensification probabilities often occur several weeks prior to changes in the USDM and in topsoil moisture and crop condition datasets compiled by the National Agricultural Statistics Service. Statistical analyses showed that the RCI-derived probabilities are most reliable and skillful over the central and eastern United States in regions most susceptible to rapid drought development. Taken together, these results suggest that tools used to identify areas experiencing rapid changes in drought indices may be useful components of future drought early warning systems.

Corresponding author address: Jason A. Otkin, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison, 1225 W. Dayton St., Madison, WI 53706. E-mail: jason.otkin@ssec.wisc.edu
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