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Earth Notes: Forecasting Flash Droughts

A dry riverbed winds through a rocky desert, with a ridge in the background and dark-colored rocks, pink soil, and one hedgehog cactus in the foreground
Melissa Sevigny
A dry riverbed at the upper end of Lake Powell, exposed by drought

Most people think of a drought as a long, slow-moving disaster. But there is a growing number of “flash droughts” around the world. Like flash floods, these are short, dramatic events that arrive without warning. Flash droughts can develop in less than week and bring intense heat and dryness.

This is a unique challenge for farmers, ranchers, and land managers who need accurate forecasts of the weather. Scientists at the University of Connecticut think there is a simple way to predict flash droughts. They developed a technique that makes use of an unusual property of plants.

Plants emit a tiny amount of the solar energy they absorb during photosynthesis as light—a kind of “glow” that can be detected by instruments on Earth-orbiting satellites. This glow is called “chlorophyll fluorescence” and it normally ramps up in the spring and early summer.

But at the first hint of a drought, plants begin to slow this activity. Scientists determined that a sudden drop in chlorophyll fluorescence can be used as an early warning system for a flash drought. In fact, it can signal a drought as much as two months beforehand. And the use of satellite data means the system can work anywhere in the world, even regions that have little access to weather data.

The team tested the idea on two flash droughts that occurred over the Great Plains in 2012 and 2017. They found it shows promise for a future warning system, especially on farmlands and grasslands. Scientists are now working to expand the research to other parts of the country and world.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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