GRAND RAPIDS, Mich. (WOOD) — Skydivers say the weather was warm when they jumped out of a plane Saturday before turning sharply colder just 1,000 feet above the ground.
These jumpers experienced first-hand a meteorological phenomenon called a “temperature inversion” — the cause of heavy fog the last few days across West Michigan.
When each diver jumped out of the plane at about 4,000 feet, the air was mild. The moment their parachutes passed the thin layer of clouds hovering about 1,000 feet from the surface, they say the temperature became drastically colder.
“It was so nice at first, and then when you got near the ground it was so cold! It made your hands hurt,” diver Mark Lytle said.
Jumpers from Skydive Allegan typically only jump through October. The nice weather Saturday prompted the dive shop to open for a day, letting trained jumpers enjoy a relatively rare December dive.
Quiet and cold December nights lately have been ideal for these “temperature inversions” to form.
WHAT’S AN INVERSION?
At night, the ground cools, sending longwave infrared radiation to the sky. Some nights, when the weather pattern and winds are quiet, chilly air gets trapped at the surface. enough moisture in the air at the surface can create low clouds and fog as the air cools and water condenses.
The layer of clouds in this picture taken by skydive instructor Kelly Winegar at Skydive Allegan shows the location of the inversion.The clouds have formed on the boundary between the cold air trapped at the surface and warm air above it. Though the fog had dissipated, the cold air was still being trapped.
WHAT MAKES THE INVERSION BREAK?
Sunshine or wind are the two main inversion breakers. Sunshine will heat the ground creating a convective current, mixing the fog out. In the winter, this can take a while because our sun angle is so low. Wind helps induce mixing vertically and horizontally. This usually helps to pull either drier or warmer air into the fog, causing it to break.