Drought Tool Expands to 48 States

Drought Tool Expands to 48 States

June 26, 2009

A seven-year research effort achieved a milestone last month when the Vegetation Drought Response Index expanded across the 48 states of the continental United States. VegDRI maps, produced every two weeks, combine satellite-based observations of vegetation conditions with climate and biosphysical information to map drought's effect on vegetation at a one-kilometer resolution.

Vegetation-based soil moisture map of U.S.

The Vegetation Drought Response Index has expanded to cover all 48 of the continental United States. (Links to larger version.)

"VegDRI provides a regional overview of how rangeland and crops are doing," said Brian Wardlow, the GIScience program area leader at the National Drought Mitigation Center, which is headquartered at the University of Nebraska-Lincoln. "For anyone monitoring agricultural conditions, particularly ranching, or with interests in natural resource management, this is an invaluable addition to their tool set."

Wardlow and Tsegaye Tadesse, NDMC climatologist, are working closely with Jesslyn Brown and staff at the U.S. Geological Survey's Center for Earth Resources Observation and Science, with sponsorship from the U.S. Department of Agriculture's Risk Management Agency, to fine-tune VegDRI. A USGS/EROS historical 20-year satellite database provides critical input for VegDRI.

"This project represents a very successful partnership between the USGS and the University of Nebraska-Lincoln's National Drought Mitigation Center," Brown said. "It shows how far we have come in recent years utilizing satellite remote sensing in combination with climate and other environmental data for operational monitoring."

In 2002, Brown and Tadesse received funding for a pilot study from the USGS to develop the concept into a drought monitoring tool for the U.S. that would complement other tools such as the U.S. Drought Monitor. In 2006, with additional RMA resources, the team began transitioning VegDRI from a research activity to producing biweekly maps for a seven-state region centered on the northern Great Plains. VegDRI's coverage has expanded each year.

Ongoing Verification; Volunteers Needed

Although VegDRI now spans the U.S. coast-to-coast, the team's work is far from over. One of its current major tasks is to see how accurately the VegDRI maps depict actual drought conditions. Work has been ongoing over 22 central and western states, for which operational maps have been produced since 2008, but this is the first year VegDRI will be produced and tested over the 26 midwestern and eastern states. The researchers are recruiting people to join the VegDRI evaluator network. Evaluators in the past have included ranchers, farmers, climatologists, extension agents, resource management agency employees, and others in the general public.

"We're really looking for input from anyone who can compare what they see on the map with what they see on the ground for their local area," Tadesse said.

To volunteer as a VegDRI evaluator, contact Karin Callahan of the NDMC, kcallahan2@unl.edu, (402) 472-7556.

Future Features

VegDRI is undergoing fine-tuning, as better and more data are incorporated. For example, Wardlow said, VegDRI maps now are based on 20 years of historic climate and satellite information, providing a sounder basis for comparison with a longer historical normal.

Additional features to be added to the VegDRI Web site in the near future include animations, change maps showing the difference between maps for the two-week interval, and an enhanced archive.



VegDRI maps and related information are available at http://drought.unl.edu/vegdri/VegDRI_Main.htm.


Kelly Helm Smith
National Drought Mitigation Center

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