As the Cicada BroodX emerge from their 17-year slumber, they not only show up in piles on the ground, they also show up in weather radars!
Weather radars send out signals into the atmosphere, and these signals bounce off anything large enough to reflect them, such as raindrops, snow, or hail. But these signals can also detect other stuff, like birds and insects!
Weather radars that can identify between precipitation (rain, snow, hail) and biological scatterers (insects, birds) are the polarimetric or dual-polarization radars. These radars send out signals in the vertical and horizontal orientation, and based on the signal reflected back they can tell the size and shape of the object. Biological scatterers tend to have a more elongated profile, so the horizontal signal they reflect is usually stronger than the vertical.
And because radar beams point upwards (and because of the Earth’s curvature), they can see stuff closer to the ground by looking at the areas closer to the radar and at higher altitudes by looking at the areas further away from the radar.
So when the weather radars see non-rain signals further away, those might be insects that can fly higher like mayflies and termites, as suggested by the radar image above from the Washington Post.
What other things do you think weather radars can detect? How are scientists using weather radars for studies that don’t involve the weather? Leave a comment!