National Drought Mitigation Center


Drought Risk Atlas updated through 2017, with 50% more stations

October 14, 2019

An update of the Drought Risk Atlas includes data from 1,124 more weather stations and 434 Snowfall Telemetry sites, as well as the 3,059 stations that were part of the original launch in 2014.

The National Drought Mitigation Center rolled out a major update of the Drought Risk Atlas (DRA) Oct. 13, with drought indices computed through 2017 based on 50% more stations, now including Alaska and Hawaii. The update includes data from 1,124 more weather stations and 434 Snowfall Telemetry (SNOTEL) sites, as well as the 3,059 stations that were part of the original launch in 2014.

The DRA provides a way to look back in time, to understand how frequently and how badly a particular location has been affected by drought. For most climate stations, the DRA provides:

  • precipitation and temperature measurements
  • Standardized Precipitation Index
  • Standardized Precipitation and Evapotranspiration Index
  • Palmer Drought Severity Index
  • self-calibrating Palmer Drought Severity Index
  • U.S. Drought Monitor
  • Drought Periods
  • Comparison of indices
  • Frequencies

Each of the numeric indices can be expressed as a time series, a table, analog ranks, or a heatmap.

Including the U.S. Drought Monitor in the DRA makes it easy to compare current conditions with past conditions, said Brian Fuchs, leader of the NDMC’s Monitoring group. “That’s what people always ask,” he said. “How does this drought compare with what has happened in the past?”

The pre-computed indices in the DRA mean that users can go download a pre-computed drought history for a station near them, and then start preparing for drought by remembering or asking what impacts occurred during previous drought periods, and what would happen if a similar drought occurred again in the near future.

Adding more stations means that it will be easier for more users to find a station near them. To add stations, the NDMC consulted with state climatologists and others about how much of a gap in the records was too much. To be included, stations must have at least 40 years’ of data, data gaps no bigger than two consecutive years, and no more than five data gaps in the past 40 years.

Most of the data is from the National Weather Service Cooperative data network, archived in the Regional Climate Centers’ Applied Climate Information System (ACIS). The update also includes data from SNOTEL sites, which collect data about snowfall as well as temperature and precipitation. SNOTEL sites are operated by the Natural Resources Conservation Service.

The NDMC, which is based in the School of Natural Resources at the University of Nebraska-Lincoln, was supported in this work by the Drought Risk Management Research Center, a Coping with Drought project funded by the Sectoral Applications Research Program of the National Oceanic and Atmospheric Administration and the National Integrated Drought Information System.

Research currently underway focuses on figuring out an ideal schedule and process for future updates, to maintain the DRA with more current data, Fuchs said.

Want expert help choosing a drought indicator? Visit the Handbook on Drought Indicators and Indices at, although all the computations in the DRA mean that the index of your choice is ready to use, pre-computed for you from the data.

Find the Drought Risk Atlas online:

-- NDMC Communications