at 10:10 AM by Mallory Schnell

Monarch Butterflies Spotted on Radar

Radar technology is normally used in Meteorology to detect precipitation; but sometimes, the radar picks up other things in the sky, such as birds or debris from a storm. Last week, the radar over St. Louis detected what was discovered to be the migration of Monarch butterflies. Meteorologists were stunned when they were presented this image; the skies were clear that morning and the signature on radar was unlike anything they had seen before.

Due to reflectivity, the forecasters knew the target was a biological one, but was different from the signature given off by birds. Capital Weather Gang wrote an article on this mystery. Here is a snippet from their piece, detailing the use of radar:

Radar is sometimes a finicky technology. It’s rooted in simple physics: send out radio waves in all directions and wait for them to bounce back. Usually, the things that radio waves bounce off of are rain drops. But often the radar can pick up other objects in the sky, like dirt and dust picked up by the gust front of a squall line, or migrating birds, or even bats as they leave their caves for their evening hunts

Monarchs migrate south to Mexico and southern California during autumn, which explains why they showed up on radar in St. Louis last Friday. Below is a map of the usual migration patterns flown by Monarchs throughout the year.

via Big Sur California
via Big Sur California

For more on this subject, check out the Capital Weather Gang’s recent article.