ROCHESTER, N.Y. (WROC) — Did you know that radar can be used to detect more than just meteorological phenomenon like rain and snow?
On a warm summer morning with no precipitation around, a mysterious green radar signature can begin to appear out of nowhere. It’s not rain, and it’s definitely not snow, so what is it?
It’s birds! Yes, radar can pick up on more than just precipitation. It can also pick up on animals such as birds, insects and even bats! Check out the radar loop below:
Early this Friday morning radar signatures picked up on multiple bird flights taking off. You can decipher this from the radar returns above, as they don’t look like normal rain passing through. The returns look like growing circles that radiate outwards as the birds take off, sort of like a firework bursting in the night sky! The birds taking off to the east of Rochester are from the Montezuma National Wildlife Refuge. The birds out towards Lake Erie appear to be from a site out in Canada. Notice how the bird take offs are coordinated with the sunrise starting from east to west. Neat right?
How does this happen?
To put it simply, radar beams send out a pulse, or an electromagnetic signal. As the radar scans this beam of energy moves away from the radar until something interferes with it. This interfering “target” can be anything from rain drops to snowflakes, birds, bats, or even water vapor and smoke.
Some of this energy will then bounce from the target object and back to the radar, which in turns scatters the energy. The appearance of the radar return back is dependent on the magnitude, position and speed of the targets being captured on radar.
It all comes down to the configuration of the radar combined with the biology of the birds moving in the lower portions of the atmosphere that result in displays that typically appear as these circular, or donut-like patterns that radiate out in reflectivity imagery on radar.
This really only happens during the early morning hours due to specific atmospheric conditions that favor this. The radar beam is bent slightly downward due to what’s called a temperature inversion. This means that instead of temperatures decreasing with height, temperatures increase with height. This makes it easier for radar to detect objects at much lower altitudes than usual.
Another phenomenon captured on radar this morning was fog that formed over Lake Ontario and rolled into the Rochester metro. Instinct tells us that anything green on radar is rain, but knowing the forecast and odd appearance it was clear that it was NOT just rain, but just tiny water droplets appearing as fog.
~Meteorologist Christine Gregory