Delicate and mesmerizing, hole-punch clouds — scientifically known as cavum — are peculiar formations that occur when airplanes cut through certain types of midlevel clouds.
These mysterious voids, with their feathery, falling wisps, are caused by supercooled droplets freezing into ice crystals, a chain reaction that creates the stunning spectacle.
Mysterious Hole-Punch Clouds
About 8 percent of Earth’s skies are covered by mixed-phase midlevel stratiform clouds like altocumulus and altostratus, which typically appear as horizontal, layered formations.
Occasionally, particularly near airports during winter, these clouds develop an unusual feature where part of the bottom seems to “fall out.” This phenomenon creates a distinctive formation known as cavum, also called hole-punch clouds or fallstreak holes. On December 2, 2024, the OLI-2 (Operational Land Imager-2) on Landsat 9 captured an image of two cavum formations in the cloud layer over Wichita, Kansas.
Seen from above or below, cavum resemble neatly cut circles or ellipses in the cloud cover. Their centers often feature feathery, wispy trails, making it appear as though the clouds are cascading downward from the sky.
The Physics Behind Cavum Formation
The phenomenon occurs in mid-level clouds containing supercooled water droplets, which remain liquid even below the typical freezing point of water (32 degrees Fahrenheit or 0 degrees Celsius). But even supercooled droplets can eventually freeze.
As an airplane passes through the cloud layer, additional cooling occurs over the wings of the aircraft and can push supercooled liquid droplets to freeze. Ice crystals beget more ice crystals, and they eventually grow heavy and fall, leaving a void in the cloud. The falling ice crystals often appear as wispy trails of precipitation, called virga.
How Common Are Cavum Near Airports?
Researchers looking at major airports around the world estimate that atmospheric conditions are right for cavum formation about 3 to 5 percent of the time overall but 10 to 15 percent of the time in the winter.
Planes passing at sharp angles produce small, circular cavum. At shallow angles, planes create long “canal clouds” with extended virga trails. Other factors that affect the length of cavum include the thickness of the cloud layer, the air temperature, and the degree of wind shear.
Every day, an average of 34 flights take off from Wichita Dwight D. Eisenhower National Airport.
NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey.
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.