Much of the U-S – including Virginia – is in a state of drought. But there is a more sudden, lesser-known phenomenon impacting the environment. WMRA’s Calvin Pynn spoke with environmental scientist Tobias Gerken about flash droughts.
TOBIAS GERKEN: Droughts are a feature of our climate system. Some are faster, some are slower. When we think about droughts, we really think about these impacts. Like, what does that actually cause if you have less water available?
Tobias Gerken is a professor at James Madison University’s College of Integrated Science & Engineering. While long-term droughts develop over the course of several months or years, flash droughts occur within a couple of weeks. So far, the conditions that drive more sudden droughts have been a mystery.
GERKEN: What we don’t understand is why certain droughts develop much faster than others. And so, the question that I’ve been working on with colleagues at the University of Wisconsin-Madison and some of the students here is to better understand: When are these droughts developing? How often do these flash droughts develop as part of a larger drought? And is there something about the atmosphere that makes these droughts happen really quickly?
And because flash droughts intensify so rapidly, they’re like a sudden shock to the system, damaging ecosystems and crops.
GERKEN: Over the span of just, like, a couple of weeks, you go from conditions that look normal – like, it’s nice and green and plants are growing, to conditions that are really, really dry. So, plants stop growing, they get stressed. Ecosystems are not functioning quite as well because they’re lacking the water.
Droughts are caused by a lack of precipitation but, as Gerken explains, there are other factors that drive their intensity beyond dry spells.
GERKEN: As plants are growing, or if the surface is moist, then water is going to evaporate…
That process is known as evapotranspiration.
GERKEN: That is going to make the air above moister. And as the surface dries, less water is being moved from the surface into the atmosphere. So, the air becomes even drier. And so, you could think about this as a potential, reinforcing feedback.
Those feedback loops are what Gerken, his students and his colleagues are focusing on as they analyze 50 years’ worth of climate and environmental data from across the U.S.
GERKEN: Once you’re already in this drying pathway, then it’s going to get harder to get out of that because there’s less water available. So, less water goes into the atmosphere. As less water goes into the atmosphere, it becomes even drier. So, you try to suck out even more water, and that is one of the things we are trying to better understand: can we quantify or can we detect these land-atmosphere feedbacks, and then can we map this to the rate of drought intensification?
Their research keeps an eye on the Great Plains as it is one of the largest agricultural regions in the world and, as such, is vulnerable to flash droughts.
GERKEN: If you think about where all the corn is being grown, all the wheat is being grown, that’s the Great Plains. It’s also a region where we know from previous research that this is really a hotspot for land-atmosphere interactions. So, there was something about the Great Plains region that makes this particularly susceptible to these types of land-atmosphere feedback.
Gerken said that’s due, in part, to the fact that the region is semi-dry – especially as a transition area between the more humid east and the drier west.
GERKEN: For these land-atmosphere feedbacks to develop, you need to kind of be in the middle. So, if you’re too dry, then you’re just lacking water. So, whenever you’re getting water, then you’re going to get evapotranspiration, but how much rain you get is really what matters. If you’re too wet, it doesn’t really matter having a little bit less water. But if you’re in this intermediate region where you add or remove water, the system really responds because you’re really in an area where these feedbacks can develop and where they can go in both directions.
The goal is to improve early-warning systems in regions where flash droughts may develop and give communities enough time to prepare for the impacts. Gerken said that could especially benefit farmers.
GERKEN: So when you think about drought forecasting, what you really need to know is: is there something that’s going to develop in the next couple of months. So, imagine that you’re a farmer and you have to make a plan. You need to decide what to plant, if to plant, or if you need to, like, buy hay because right now nothing is growing. And so, typically farmers would be cutting hay, but it’s not there. So, if you need to make these decisions, then you need to have lead time. You need to know a couple of months in advance whether something like that is happening.
As their research continues , Gerken and his students have been presenting their findings at national conferences, and are working on a peer-reviewed paper.
For WMRA News, I’m Calvin Pynn.
Full disclosure, James Madison University’s Board of Visitors holds WMRA’s operating license.
