Interactions between the air and the surface of the Sea

Luke Groskin joins Hari Sreenivasan to discuss Hurricanes and the devastation it causes.


Joining me now is 'Science Friday' video producer Luke Groskin.

You know, before we talk about building a hurricane in a box, define just what is a hurricane?

We all know the devastation that they cause, but what's happening weather-wise?

Well, obviously it's a storm.

It's a cyclonic, a spinning, storm that feeds off the heat of the ocean.

It's usually a low-pressure system usually.

I mean, we think of hurricanes in the Atlantic.

I think they're called cyclones in the Pacific.

They spin the opposite direction, and so the hurricanes, they start forming off the coast of Africa, and they start churning up all this heat, pulling up all this heat from the Equator, from the ocean along the Equator, and they build up speed, and they come colliding with, usually, the United States coast.


So how do you re-create something like that in a laboratory?

Well, you can create all the environmental conditions that are going on in the laboratory, so, I mean, you're not creating the overwhelming devastation, obviously.


But you are creating the wind speed.

You are creating the storm surge.

You are creating the heat.

You are creating the droplets that you would experience on the surface of the ocean during that storm, and all of that provides an enormous amount of information that you can't get from an actual hurricane.

You can't put a buoy out there and get the level of granular detail that these guys are getting in the lab at the University of Miami.

So tell me about those details.

I mean, what are they able to measure while they have turned on kind of the perfect hurricane?

They've got the warm water.


They've got the wind speed.

So the big things that they're looking for are, they're looking for the interaction between the actual ocean waves and the air above it.

So in a Category 5 hurricane, you really can't tell the difference between where the ocean stops and the air above it begins.

There is so much spray.

There is so much water getting whipped up off those waves, and you can see it in the video.

It's just... It's this really amazing, intense visual, and so much water droplets are getting lifted up.

Now, if you watch those things in slow motion, you can get a sense of how much water is actually being lifted up, how small those droplets are, how much energy is coming up with those droplets, and all of that informs how much energy is going to be lifted up into the air and then become part of this large storm system.

How do you get wind speeds that high in a controlled environment?

An enormous diesel generation and in a really, really tight funnel.

So it starts as, you know, this 25-foot... it looks like it's 25-by-25-foot set of fans, and that... All those fans are blowing towards this one tunnel, and they get consolidated.

All the air gets consolidated into one tube faster and faster.


Everything gets squeezed into this tight tub and then projected over this very narrow space, this box, and that allows you to create 200-mile-per-hour wind speeds.

What kind of discoveries have they made already, and what's the breakthrough that they're still looking for?

Well, the big thing that they're looking for, the big thing that's going to change people's lives, hopefully save people's lives, is this notion of the drag coefficient.

So the drag coefficient, you can think about it this way, is that if I rub my hand across the surface of this table, it's nice and smooth, and, you know, scientists and meteorologists thought that when you did that with a hurricane, when you run those winds of the hurricane over the surface of the ocean, you would have so much spray, it should be so smooth.


So their research has shown that after a certain point, you know, wind the wind speeds get built up, you don't get more drag out of it, so it levels off.

The drag coefficient levels off.

Now, if that's the case, Category 5 hurricanes shouldn't exist.

They shouldn't.

They just shouldn't exist.

There should be so much drag that the wind speeds shouldn't be able to get up to that level.


That's not the case, so they want to look on a very granular level.

What is going on here on the surface of the ocean with all this spray that allows a hurricane to get so fast so quick?

You know, I'm thinking recently of Hurricane Matthew and how when it made that turn up into the Gulf, it suddenly just... It went from, I think, like, a Category 1 or 2 to a Category 4 or 5, and it was almost overnight.

And what they want to do is, that drag coefficient and understanding it will get fed into the models that meteorologists use across the United States.

This kind of information feeds to meteorologists, and the meteorologists are able to predict better the type of intensity of the storm and obviously where it goes and so forth, and that way they can help people prepare to get out of the way faster.

Exactly, exactly.

You know, when you see those plots on the map where it's like, 'Oh, it could go this way.

It could go that way.

It could go this way,' usually meteorologists have a clear sense of, like, you know, exactly the rough region where it's going to hit.


What they don't know oftentimes is how hard it's going to hit and how much rain it's going to dump and, you know, how fast the wind speeds are going to be.

That's the level... That's where this sort of information, this lab, can really make a huge difference.

Nobody has had the ability to create a 200-mile-per-hour wind and see what that actually does to the surface of the ocean.

Like I said, you can't actually put monitoring equipment in the ocean while the hurricane is there or... you know, it's kind of like, you know, the movie 'Twister' where you try to, you know, put a buoy or... they put the thing in front of the twister, and then it goes up and it creates... They get all this data.

You can't really do that in a hurricane.

You have people that are flying over it, but you can't really tell what's going on right at the surface, and that's the amazing thing about this hurricane in a box that they've built, is that they can really look at the granular details there, and that has an enormous effect on the forecast model.

So when wind goes over water at 200 miles an hour, is it still water?

I mean, is it just spray?

Is it something that, like a mist?

Yeah, they call it spray.

They call it spray, and it's actually kind of terrifying.

It's this extremely violent surface, and, to me, it was kind of fascinating that they're, you know, they're using these 10,000-frame-per-second cameras to look at, on the centimeter scale, what that spray looks like, and you look at it, and it just looks kind of violent, but they're able to actually quantify it.

Anything coming at you at 200 miles an hour was going to hurt you, even if it's water.




If you're in some of these incredible winds, you're going to get hurt...


...just by standing in the water alone.


I mean, the number one question that they get is from people, especially very silly meteorological reporters is, 'Can I go in there during the...Can I actually step inside this box?'

Once you see this thing on, you're like, 'No. That's nuts.'

You would not want to be inside this thing.

It looks painful.

It looks dangerous.

I don't envy those people that end up going out in hurricanes.


Maybe that'll help convince some of these meteorologists not to do that.

All right, Luke Groskin, thanks so much for joining us.

Thank you.