You know about flash floods, but what do you know about a flash drought?

This week, we learn what goes into creating a flash drought and how glowing plants can alert us to an upcoming flash drought.

Bill Burton: It is time for us to take a look at the Science Behind the Forecast as I am joined this Friday morning by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.

Tawana Andrew: Good morning. I could say that this topic is not a very dry one.

BB: Well said. And it involves the word flash, which I generally think of, you know, as in flash of lightning, or maybe flash flood. But this is flash drought that we're going to be talking about today. Explain, please.

TA: So usually a drought is a, you know, slow, evolving scenario takes weeks or months, right? But, but sometimes a drought can develop or even intensify in a couple of days or weeks. So with a flash drought, that can occur during spells of low precipitation, which we typically expect, but that is coupled with abnormally high temperatures, like during a heat wave, strong winds, low humidity and intense solar radiation. So you have all of these things going on, and with the above normal temperatures, especially, that helps to amplify evapotranspiration, that is our Word of the Day. So during evapotranspiration, the water is evaporated from the ground and transpired from plants, and the increased evapotranspiration significantly lowers soil moisture, and that can rapidly create or intensify a drought, and then you get that flash drought. With a conventional drought that can occur in any location at any time of the year. However, flash droughts usually happen during our warmer seasons, so researchers have found that flash droughts are more common in the eastern and central US, including Kentucky and Indiana during July and August. Hey, we are basically right there, right now.

BB: Right in the middle.

TA: So changes in evapotranspiration are typically an indicator of an impending flash drought. So a 2019 study that found that increased evapotranspiration caused by temperature, radiation or wind changes, all preceded all of the flash droughts that they studied. So every single one of them. And by the way, only five to 10% of flash droughts actually became the lengthy, longer droughts that we're typically hearing about in news and weather. So one way that NASA is working to try to predict some of these flash droughts is using the glow of plants.

BB: The glow of plants?

TA: Trust me, this was one that got me too. So as plants photosynthesize, the chlorophyll will actually release unused photons creating a glow called solar induced fluorescence. So this glow is typically stronger with a plant that is absorbing more carbon dioxide as it's starting to grow a little bit more. So we can't actually see this glow, but NASA has a cool satellite called The Orbiting Carbon Observatory 2. Because, of course, as scientists, we name things very well, and they use this to track plant fluorescence between 2015 and 2020, and the researchers found that plants emitted a stronger than normal fluorescent signal in the months and weeks leading up to a flash drought, as they're pulling all of this moisture from the soil. And then once you had those abnormal weather conditions like the heat waves or strong winds or a lot of sunshine, then you end up with a flash drought in those locations. Who knew that plants literally glowing can help with predicting flash droughts, which is great.

BB: That fern is positively glowing!

TA: And that fern can help us really look ahead to a potential flash drought, and maybe help prevent billions of dollars in economic losses. So be nice to your plants. They are glowing for a good reason.