The Making of the Weekly Drought Map
[Written by NOAA] It’s hard to miss a hurricane, given that storm forecasts dominate news coverage for as much as a week in advance of landfall.
Drought, by contrast, can surprise you, slowly building in severity until it causes billion-dollar losses affecting agriculture, water resources, energy production, and public health. It now ranks second—behind tropical cyclones—on the list of leading U.S. billion-dollar disasters.
Drought is a slow-motion disaster, and the effort to limit its damage is led by the United States Drought Monitor (USDM), a weekly map produced by the National Drought Mitigation Center (NDMC) at the University of Nebraska–Lincoln, the U.S. Department of Agriculture (USDA), and NOAA. NCEI scientists are among the authors of the monitor, and NCEI data feed into the assessment.
U.S. Drought Monitor 9-17-20: Dry weather dominated the West, leading to drought intensification as wildfires burned thousands of acres. Heavy rains led to some improvements in the Rockies, Plains and Midwest. Drought covers about 32.8% of the U.S. and Puerto Rico. pic.twitter.com/iUqLdcdZMR
— Drought Center (@DroughtCenter) September 17, 2020
The U.S. Drought Monitor is updated weekly because the information matters to people—for growing crops, managing water supplies, generating power, and fighting wildfires. The USDA uses the map to determine eligibility for monetary relief, and state and local authorities use it to trigger responses related to issues such as reservoir levels.
The stakes are high, and those who use the map aren’t always happy with what they see on it—partly because the USDM reflects several types of drought at multiple time scales, all on a single map. To withstand the criticism, the authors need to have thick skin and confidence in their methods.
“We have to basically put force fields around us to deflect the harassment and the political influence,” says Richard Heim, an NCEI scientist and an author of the U.S. Drought Monitor. “The map and process must be totally objective.”
Gathering Drought Data
The U.S. Drought Monitor releases maps detailing the location and intensity of drought in the 50 states, Puerto Rico, and U.S.-affiliated Pacific Islands and Virgin Islands. The maps show blobs of yellow, beige, orange, and red, indicating levels on a scale that ranges from Abnormally Dry (D0, yellow) to Exceptional Drought (D4, deep red).