How to improve tornado warnings using infrasound
OSU Research Matters is a bi-weekly look inside the work of Oklahoma State University faculty, staff and students.
All around us are sounds that we cannot hear that are capable of traveling over extreme distances, even around the Earth. Just like regular sounds, these sounds carry information about what made them. This is how you could be blindfolded and still know where someone is in the room if they are talking.
Oklahoma State University professor Dr. Brian Elbing and his team has been listening to these sounds for six years with some of the detections being from explosions, earthquakes, fireballs, and tornadoes. Tornadoes have been the primary focus, with the goal being to determine what exactly produces the sound and whether it can be used to improve warnings. More recently, they have begun listening for earthquakes from high altitude balloons as part of a collaboration with NASA JPL and Sandia Labs. This work uses Earth has a model for Venus to see it could be used to study the structure of Venus, which is too hot to have any sensors on the surface.
In this episode, Meghan Robinson speaks with Dr. Elbing to learn more about how we can use infrasound to improve tornado warnings.
ELBING: So, tornadoes, they emit the sound that's at frequencies below what humans can hear. We call it infrasounds. It's kinda like, have you ever heard of infrared, that's like light that you can't see. This is sounds that you can't hear, and tornadoes seem to admit it, and it carries over long distances and carries information about its formation, what's going on. It's not that critical in Oklahoma, where we have flat terrain and radar does an excellent job. But this is becoming a big problem in the Southeast as Tornado Alley seems to be shifting eastward and most deaths from tornadoes are happening in the Southeast, not in Tornado Alley. And, infrasound would be much more effective there because it's less sensitive to terrain.
ROBINSON: Dr. Elbing and his team use microphones to identify sound. They’ve learned that tornadoes will produce infrasound as they develop – before they touch down. He explains why this research will be most beneficial to Southeastern United States.
ELBING: Most of their tornadoes happen at night, and storm chasers don't go there. Radar's a line of sight measurement. So if you have a hill, and you're on the backside of the hill, There's nobody that's gonna see that. Radar's not gonna see that. [In] the upper atmosphere, they'll see some kind of signature. But the uncertainty definitely increases the farther from the ground you are for that measurement. I have been working on the, on the warning side of it. But there's others, they envision if you can get the signature of the tornado known, and you could automatically detect that sound, you could have individuals with their own sensors in their house that go off if it detects that signature.
ROBINSON: You keep talking about the Southeast, that terrain is very different. So how is it beneficial to study in Oklahoma where the terrain is very flat to use that in a more hilly terrain?
ELBING: Yeah. Well, the advantage we have is we live in a state that's kind of the best for being able to see and track tornadoes. The analogy I like to give is if you closed your eyes right now, and I was walking in this room, you would know right where I was and if I dropped a glass, you would know I did that, right? And all that is a combination of experience and your two ears. And so, you've learned a bunch of signatures of sounds, and you use that to infer what's going on. And what my work is doing is trying to establish that connection. So I need ground truth, which is good radar measurements of what the tornado actually is and doing, along with the acoustic signatures.