Photograph by National Park Service, Rex Features/AP
Smoke and Mirrors
McCollum warned against confusing the two concepts of fog (pictured in the Grand Canyon on December 1) and temperature inversion.
While temperature inversion refers to the sandwiching of cold ground air between warm ground and air, fog is a collection of water droplets that typically form over bodies of water. A temperature inversion can cause a fog, but a fog can't cause a temperature inversion.
"Freezing fog dominated yesterday and is reflected in great patterns on this Kaibab Limestone. By the end of the day, the sun was able to burn it all away"—making for a surreal scene of floating above the canyon, the National Park Service said in a statement. (Watch a video of the Grand Canyon.)
Photograph by National Park Service, Erin Whittaker, AP
A sea of clouds is seen filling the entirety of the Grand Canyon on November 29.
The fog "simply drained into the canyon," McCollum said. "Within 48 hours [of the rainstorm, the fog] expanded to fill every valley in northeast Arizona via the Colorado River."