Researchers Developing Tool to Help Oklahoma Farmers Predict Drought

September 9, 2014

Weather researchers are developing a new tool they say could give Oklahoma farmers and ranchers as much as a month’s warning when drought conditions are on the way.

The Evaporative Stress Index is a system being developed by the U.S. Department of Agriculture that uses satellite data to predict drought, The Oklahoman reported. An experimental version of the index is online, and researchers expect the full version to be available next year.

Jason Otkin, an assistant scientist in the University of Wisconsin’s Cooperative Institute for Meteorological Satellite Studies, said the system uses data that show how much moisture plants give off into the atmosphere to predict dry conditions.

As plants draw water from the soil, they release water vapor into the atmosphere through small pores on the underside of leaves, a process called transpiration. Otkin, a member of the team developing the system, said when water becomes scarce and plants are stressed, they give off less water vapor. That change takes place before plants show visible signs of stress like wilting or changing color, he said.

By tracking the amount of moisture plants give off, the system can give farmers and ranchers an idea of when drought conditions are about to appear or intensify, Otkin said. The system can show drought predictions within a window of about 2 to 3 miles, he said.

The tool will be particularly useful for cattle ranchers, Otkin said. For obvious reasons, cattle are more mobile than wheat crops, so when drought is on the way, ranchers have more options for preparing for it.

“Once the wheat’s in the ground, it’s in the ground. There’s not much you can do about it,” he said. “But for ranchers, there is something you can do about it.”

Much of Oklahoma has been in the grip of a persistent drought since 2010. Although a relatively cool, rainy summer has helped the situation, conditions remain dire in parts of western Oklahoma. According to a U.S. Drought Monitor report released Thursday, about 16.6 percent of the state is still in extreme or exceptional drought, the report’s two most severe categories.

Mark Shafer, director of climate services for the Oklahoma State Climatological Survey, said the index will also serve as a good predictor of flash drought.

Flash drought occurs when abnormally hot, dry weather causes drought conditions to appear and escalate quickly. Oklahoma’s hot, dry summers coupled with high winds make the state particularly prone to the phenomenon.

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