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ALIENS!? Just what exactly was on the weather radar Saturday night?

Social media lit up Saturday night with questions of what was making the strange rings on the radar.

DALLAS — "Are we being invaded? Crop rain circles? WHY AREN'T YOU TALKING ABOUT THIS!!???"

These were the types of questions that came flooding in on social media to WFAA on Saturday night.

While it make look extraterrestrial, there is actually a simple answer for what the radar is showing.

The reason the radar looked this way is from something called superrefraction.

Normally, when a radar beam travels away from the radar, it becomes higher off the ground the farther away from the radar it travels because of the curvature of the earth.

This is normal, and it is called "normal refraction".

Credit: WFAA
Normal refraction of a radar beam.

However, when there are calm, cool, and dry conditions-- even more specifically, when moisture and temperature decrease sharply with height-- "superrefraction" can happen to the radar beam.

These conditions were in North Texas on Saturday night.

When superrefraction occurs, the atmospheric conditions cause the radar beam to curve back closer to the surface of the earth. The beam travels lower than it would under normal circumstances.

Credit: WFAA
Superrefraction of a radar beam

This causes the beam to hit things that are closer to the ground as well. Things like birds, bugs and dust. If conditions are ideal, it can even hit buildings, trees and cars.

And that gives us the green rings you might have seen on the radar Saturday night. We had clear skies, so it was not rain. 

The radar was hitting birds, bugs and so on, but the radar made it look like rain. We call this "ground clutter" instead.

So there ya go! A simple explanation much more boring than an alien invasion.

Credit: WFAA
What is superrefraction?

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