Climate & Health – Drought Severity
This indicator reports the population-weighted percentage of weeks in drought during the latest three-year period.
Source
Source Description
The U.S. Drought Monitor, established in 1999, is a weekly map of drought conditions that is produced jointly by the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture, and the National Drought Mitigation Center (NDMC) at the University of Nebraska-Lincoln. The U.S. Drought Monitor website is hosted and maintained by the NDMC. The map is based on measurements of climatic, hydrologic and soil conditions as well as reported impacts and observations from more than 350 contributors around the country. The U.S. Drought Monitor, a composite index that includes many indicators, is the drought map that policymakers and media use in discussions of drought and in allocating drought relief. For more about this source, please visit the United States Drought Monitor web page.
Methodology
This indicator reports the percentage of weeks in drought, by drought severity level. Data are based on analysis of weekly Drought Monitor shapefiles, where drought is defined as a moisture deficit bad enough to have social, environmental or economic effects. This Drought Monitor weekly analysis reports the area of the United States experiencing drought, by drought severity level. D1 is the least intense level and D4 the most intense. D0 areas are not in drought, but are experiencing abnormally dry conditions that could turn into drought or are recovering from drought but are not yet back to normal.
156 weeks of data presented in this format were analyzed by CARES to generate the 3-year average drought statistics shown here. Analysis involved intersecting census block group centroids with each of the weekly US Drought Monitor shapefiles. Resulting figures show the percentage of weeks that the report areas experience drought at each of the Drought Monitor levels. The percentage of weeks in Any Drought includes levels D1 through D4. Report area figures are population-weighted based on the following formula:
Percentage = [ SUM( Number of Weeks at Dx * P ) / SUM(Total Weeks * P) ] * 100.
Where Dx is the drought severity level and P is the population of each census block group.
For more information about the original data used in this calculation, please see the US Drought Monitor US Drought Monitor GIS Data Archive web page.
Data Breakouts Available
- Annual Weeks in Drought, Percent
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