The picture you see here was shared earlier in the summer by Dr. Tim Coleman. What you are looking at are mayflies that took to the sky one evening along the Black Warrior River. The picture certainly looks like something that may be out of a horror movie but this is far from the case. These insects tell us a lot about the health of our ecosystem. I stumbled upon an article yesterday that reminded me of this picture and it talks about how Doppler radar is being used to improve the study of this species.
A similar emergence of mayflies occurred back on July 20th within the Upper Mississippi River Valley. The radar image below shows a bright north-south oriented return that was a massive swarm of mayflies rising from the Mississippi River.
Radar (Radio Detection And Ranging) is a method of active remote sensing that uses a beam of energy to detect a target. That target however may not always be a raindrop. You often hear us use the term ground clutter. This is the colorful ring near a radar site that is the result of refraction of the radar beam.
This often happens on clear nights when the surface cools quicker than the air aloft, resulting in an inversion. This atmospheric condition causes the radar beam to bend closer to the earths surface. This Superrefraction as it's called, allows the lowest level radar scans to detect nearby buildings and terrain features.
Sometimes the radar can detect smoke plumes, bird migration, or even insects, especially when it is in a very sensitive mode. Furthermore, Dual pole radar’s capability to determine the size of targets has allowed for major improvements in debris detection during severe weather events.
(The ring in this animation represents a group of birds leaving their roosting site. NWS Green Bay, WI)
The ability to view these large swarms are important to scientists as it helps with monitoring the delicate ecosystem. According to the La Crosse, WI Fish & Wildlife Conservation Office, this is an event that is seldom observed in other parts of the world. The La Crosse, WI National Weather Service has a webpage dedicated to documenting these events in cooperation with organizations such as the U.S. Fish and Wildlife Service (https://www.crh.noaa.gov/arx/?n=mayflygeneral#July202014). Observations like this always remind me that we should keep an eye on radar even on the sunny days. You never know what you may discover!
Fox6 Meteorologist Wes Wyatt