As far as natural disasters go, tornadoes can be some of the most dangerous. And that's not only because they're deadly funnels of debris-filled winds whipping around at hundreds of kilometers per hour. They're also a problem because they can be unpredictable. In some cases tornadoes strike with little to no warning, making them extremely dangerous to the people in their paths. Which is why scientists have launched a new mission to detect weather conditions that are likely to produce tornadoes well before a funnel actually forms. And the best part is they're doing it from space. 

These days most weather predictions come from observations made using ground-based radar. The way it works is transmitters send out a short powerful pulse of microwaves, which can travel more than a hundred kilometers out in every direction. When those waves encounter water droplets, like in clouds and rain, they bounce back and get picked up by a receiver. Meteorologists can use the microwaves' travel time to calculate the distance to the storm cloud. And they can track the clouds' location and movement based on the direction and Doppler shift of the reflected waved. Basically waves bouncing off clouds coming towards the receiver get scrunched up, while waves bouncing off clouds moving away from the receiver get stretched out. And forecasters can measure that stretching or scrunching to calculate how fast the clouds are moving toward or away from the location of the receiver. 

And that's all great, but the method has some serious limitations. For one, it only works if you have operational radar stations covering the area that you're interested in. Which isn't always possible in remote or extreme locations. Plus radar observations aren't continuous. And tornado conditions can evolve quickly so if that happens in the gap between radar measurements, it's easy to miss. These are two big reasons why twisters can strike without much warning at all. And there is one untapped clue that can go a long way toward predicting tornadoes, and that's lightning.

Tornados typically form during thunderstorms when warm moist air and cold, dry air travel past each other in different directions or at different speeds. When these opposing air masses intersect and flow over one another, they start to twist and suck in more air. They quickly build in speed and intensity, forming the seed of a twister. And as these storms develop, they often produce a lot of lightning. That's because thunderclouds have lots of winds moving both upward and downward and all of these drafts carry droplets of water and ice with them. As ice and hail that are moving downward collide with water particles that are moving upward, they shave electrons off the surface of these particles and whisk them downward. That gives the lower part of the cloud a negative charge and the higher part of the cloud a positive charge. Most of the time. Once enough charge builds up, it will suddenly arch through the air to equalize the charges, creating lightning.

Research has shown that the number of lightning strikes rapidly increases just before a severe storm starts to take shape. Obviously not every lightning storm spawns tornadoes, but observations of lightning alongside measurements of wind speed and direction can tell us when conditions are ripe for a tornado. 

There's just one problem with this. Scientists estimate that at most a quarter of all lightning actually reaches the ground. Most of it happens in the clouds, making it hard to spot, especially during the day. So in the past, forecasters couldn't really rely on detection of lightning to figure out that tornado weather was brewing. But in recent years, meteorologists have turned their attention to a promising new way of making weather observations from a lot further away.

Geostationary operational environmental satellites, or GOES for short, are a group of satellites positioned nearly thiry-six thousand kilometers above earth. They're in a geostationary orbit. Meaning that as earth rotates, they always stay positioned above the same spot. That makes them really good at keeping an eye on the changing surface of our planet, including it's weather.

One of the latest ones launched in 2016 carries a new instrument call the geostationary lightning mapper. Or GLM. GLM essentially consists of a camera sensor that continually observers earth, picking up radiation in the near infrared part of the electromagnetic spectrum.

That makes it perfect for detecting hot spots in our atmosphere. And since it has a sharp resolution, and records 500 frames per second, the spots it picks up can be really small and fleeting. 

500 frames is a lot. The camera we're using to record this right now is 24 frames per second. In other words, it's designed specifically for spotting lightning. And the near-infrared radiation it detects can pass right through clouds, so the GLM is able to see lightning happening anywhere, during the day and at night. Since tornadoes are usually born out of developing storm fronts, this detection of lightning helps meteorologists predict when and where the twisters might form. And by making continuous measurements, the GLM is much less likely to miss the critical moment when a dangerous storm that starts to evolve. 

On top of that, the satellite's huge field of view makes it possible to capture a complete picture of the weather in a region, including in remote areas where radar coverage is poor. This means that satellite detection of dangerous weather can be much more reliable and accurate than radar observations. 

Today, near real time data from GLM is being used to monitor storms over the Americas. And that's made it possible for forecasters to issue severe thunderstorm warnings five to 20 minutes earlier than they could with just radar. In the case of thunderstorms that develop into tornadoes, this much notice could mean the difference between life and death. So far the lightning mapper has proved so useful that the instrument was also installed on the most recent GOES satellites, which launched in 2019 and 2022. Because sometimes, you just have to go all the way to space to see exactly what's happening here on earth. 

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