On January 6, NASA’s Terra satellite captured this natural-color image of steam-fog forming over Lake Michigan and Lake Superior and streaming southeast with the wind.
In early January, a swirling mass of Arctic air moved south into the continental United States and began breaking off from the polar vortex, a semi-permanent low-pressure system with a center around Canada’s Baffin Island. The frigid air was pushed south into the Great Lakes region by the jet stream, bringing abnormally cold temperatures to many parts of Canada and the central and eastern United States.
When the cold air passed over the relatively warm waters of Lake Michigan and Lake Superior, the contrast in temperatures created a visual spectacle. As cold, dry air moved over the lakes, it mixed with warmer, moister air rising off the lake surfaces, transforming the water vapor into fog — a phenomenon known as steam-fog.
The image above is the same as at the top of this post, but it’s a false-color image. It helps illustrate the difference between snow (bright orange), water clouds (white), and mixed clouds (peach). Water clouds are formed entirely by liquid water drops; mixed clouds contain both water droplets and ice crystals.
Eleanor Imster has helped write and edit EarthSky since 1995. She was an integral part of the award-winning EarthSky radio series almost since it began until it ended in 2013. Today, as Lead Editor at EarthSky.org, she helps present the science and nature stories and photos you enjoy. She also serves as one of the voices of EarthSky on social media platforms including Facebook, Twitter and G+. She and her husband live in Tennessee and have two grown sons.