A rare optical illusion known as a fata morgana can really mess with your mind. Seen in a narrow band just above the horizon, it is a superior mirage that makes distant objects appear warped and much closer to you than they actually are.
A fata morgana is created when cold, dense air near the Earth’s surface is trapped beneath a layer of significantly warmer air aloft, known as a temperature inversion. This causes light rays from distant objects to refract, or bend, downward toward an observer standing on the ground.
This tricks our brains into seeing the objects as if their refracted light traveled in a straight line rather than bending as it passed through the layers of varying temperature within the inversion. Distant mountains will appear warped or stretched in a fata morgana, making them seem both taller and closer than they actually are because the observer is typically viewing several such mirages stacked on top of each other.
Meteorologists at the National Weather Service in Goodland, Kansas, witnessed a fata morgana outside their office on Oct. 5, 2021. A view toward the east just after sunrise showed a superior mirage in the form of a distorted hill or mountain that seemed out of place in the flat terrain of western Kansas.
Residents of Fairbanks, Alaska, have witnessed this a few times in recent years as well. The city is situated in the Tanana River Valley and is surrounded by hills and mountains on all sides except to its south.
Cold air is denser than warm air, so it can sink down into the valley and lead to a temperature inversion with warmer air in the hills and mountains surrounding Fairbanks.
A fata morgana from the office this afternoon of Clear Creek Butte 12 miles south of the airport. Essentially, a fata morgana is a density difference of the air above and below an inversion making an object appear inverted. pic.twitter.com/t3ZBzVlt41— NWS Fairbanks (@NWSFairbanks) January 21, 2020
But fata morganas aren’t just confined to central Alaska and western Kansas. In December 2020, a college professor in Madison, Wisconsin, spotted one in the Badger State’s capital city. Blue Mound, a relatively small hill west of Madison, looked more like a mountain because of this superior mirage.
Per one of my AOS professors, there was Fata Morgana over Madison this morning!— Amanda Morgan (@amorganwx) December 2, 2020
It caused Blue Mound, which usually looks like a small hill, to look more like a mountain!
📸 Tim Wagner#wiwx pic.twitter.com/zJUqcRmKxt
While not as eye-catching, a keen meteorology professor in Oswego, New York, caught a fata morgana in March 2021. The shoreline of southern Ontario, Canada, which is essentially flat, could be seen as a hill from the other side of Lake Ontario – a distance of over 40 miles. On a typical clear day, you cannot see Canada from this location along the southern shore of Lake Ontario.
A cold Lake Ontario actually created this inversion. Water temperatures in late March are generally in the 30s coming off a cold winter. Air temperatures away from the lake were in the 60s on March 22, when the fata morgana was observed, so there was a sharp temperature contrast between the cold air near the lake surface and the warmer air aloft and inland.