Sushmita Pathak
Appearances
Short Wave
Tornado Alley: Home Of Extreme Winds
So now you have a spinning column, a rotating thunderstorm. And if the conditions are right, that rotating column can stretch to the ground and that's how you have a tornado.
Short Wave
Tornado Alley: Home Of Extreme Winds
So the questions researchers really had was like, if there's this like similarities in geography of these two continents, why doesn't Central South America have a tornado alley?
Short Wave
Tornado Alley: Home Of Extreme Winds
So the starting point of the research was really like the geographic setup in Central North America and Central South America is kind of similar. But South America does not get as many tornadoes, even near as many tornadoes as North America does. And so... they really wanted to figure out why there was this huge contrast.
Short Wave
Tornado Alley: Home Of Extreme Winds
And what they found was it was because of a surprising new ingredient, which is the roughness of the land surface many, many thousands of kilometers away from where the tornadoes were actually happening. So when the easterly winds are coming over the Gulf of Mexico towards central North America, Tornado Alley, that's a relatively smooth surface, this vast expanse of ocean.
Short Wave
Tornado Alley: Home Of Extreme Winds
So winds don't really encounter any resistance. They can build up a lot of speed. And that's really important for wind shear, which is very important for tornado formation. But in South America, what happens is those easterly winds are blowing over the Amazon rainforest. So you have a lot of vegetation, a lot of hills, so a very rough surface.
Short Wave
Tornado Alley: Home Of Extreme Winds
And because of this rough surface, the winds get broken down. And so the tornado potential also gets suppressed.
Short Wave
Tornado Alley: Home Of Extreme Winds
Just the region near the equator from where the easterly winds are coming into those regions.
Short Wave
Tornado Alley: Home Of Extreme Winds
And to test this sort of hypothesis and to arrive at their findings, the researchers tested this out in a global climate model, which is like a computer simulation of the Earth. Scientists use it all the time to learn about climate patterns and figure out how they'll change in the future. So in this global climate model, you can sort of tweak different parameters to see how things will change.
Short Wave
Tornado Alley: Home Of Extreme Winds
And so what the scientists did was they replaced the Gulf of Mexico with forests to make it kind of rougher. And when they did that, they saw that tornado potential in the US, in Tornado Alley, it went down. Wow. And similarly, when they smoothed out the Amazon forest, tornado potential in Central South America went up.
Short Wave
Tornado Alley: Home Of Extreme Winds
And I say tornado potential here because the model cannot produce tornadoes exactly. It can only simulate the environment, the instabilities that lead to a tornado. So that's just a small but important caveat.
Short Wave
Tornado Alley: Home Of Extreme Winds
Yeah, it is. It is pretty solid. And I asked another scientist who was not part of the research about limitations, and she was like, this feels like a pretty solid study. And actually, she studies how land cover in the vicinity of the storm, like a mile or two miles, pretty two-mile radius of the storm changes tornadoes. And so she was actually surprised.
Short Wave
Tornado Alley: Home Of Extreme Winds
She was actually very fascinated by this, that land cover and terrain so far away from the actual storm can also affect tornado potential. So...
Short Wave
Tornado Alley: Home Of Extreme Winds
We're talking about hundreds of miles away from where the tornadoes are actually forming, from where the storms are actually forming.
Short Wave
Tornado Alley: Home Of Extreme Winds
There are a lot of implications because, you know, we as humans do a lot of things that can change the roughness of the terrain. Like when you cut down forests, it's like smoothing out the surface. That's already happening in the Amazon with deforestation. Or when you set up large scale wind farms on a vast flat expanse, it can make the overall surface rougher. That's happening in the Midwest.
Short Wave
Tornado Alley: Home Of Extreme Winds
So the authors of the study really want to bring attention to this point that there are a lot of different things that affect tornadoes and that lead to tornado genesis. And one thing that's not been looked into till now is this large scale surface roughness or the roughness of the terrain very, very far away from where the storms are forming. So this was the big takeaway.
Short Wave
Tornado Alley: Home Of Extreme Winds
So the short answer is we don't know how climate change will affect tornadoes. Now, research does suggest that we have more storms in a warmer world. And there are some studies that suggest that climate change may be shifting tornado alley in the U.S. towards the east. But tornadoes are very complex.
Short Wave
Tornado Alley: Home Of Extreme Winds
They are so unpredictable and they are so complex that it's hard to attribute changes in tornadoes to climate change. It's very easy to say, oh, this heat wave was caused because of climate change or this really heavy spell of rain can be attributed to climate change. But you can't do that very easily with tornadoes. And they're also still kind of mysterious, like
Short Wave
Tornado Alley: Home Of Extreme Winds
we don't fully understand what factors have to come into play in what exact measures for a tornado to form. So all this makes it hard to establish a clear, definite link between climate change and tornadoes. But that said, I think in order to understand how climate change will affect tornadoes, we have to first understand...
Short Wave
Tornado Alley: Home Of Extreme Winds
tornadoes are formed and what leads to a tornado hotspot and the findings of this study you know get us a little bit closer to that and so I think going forward I think the broader takeaway is that you know when we think about how a changing climate will affect storms in general including tornadoes we should not only think about rising temperatures but also changes in terrain because that also affects storms and severe weather.
Short Wave
Tornado Alley: Home Of Extreme Winds
You need cold, dry air coming in from one direction. Like from the Rocky Mountains. You need warm, humid air coming in from one direction.
Short Wave
Tornado Alley: Home Of Extreme Winds
And you also need like these strong gusts of wind that are a little bit higher up in the sky that kind of like exert that force.