Turning Fog Into Snow
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What can you do when you find yourself wrapped in fog? Hi. I'm Dave Thurlow and this is the Weather Notebook. When socked in by low fog, most of us take a minute, slow down, and settle into the soft landscape. But science is working on new ways to make ground fog go away.

Fog itself is nothing more than a cloud on the ground. There two kinds warm fog, when the air is above freezing, and cold fog, when it's below 32. One method of getting rid of warm fog was used in England in World War II, but as you'll soon understand, it never caught on in peacetime. Military airports were lined with trenches that held gas or other fuel. When the pea soup rolled in, the trenches were set ablaze. The rising thermals then lifted the fog. Not comforting to frequent, non-wartime fliers!

Cold fog is less common than warm fog, though it is frequent during the winter in the valleys of the western U.S. and has the attention of researchers at the University of Utah. They know that cold fog, made up of tiny water droplets will become snow crystals as soon as they find something to condense on. These scientists are spraying carbon dioxide--CO2 into the fog, which causes the water droplets turn to ice crystals, and then the fog literally turns to snow.

In one test, they cleared the fog from an area about six miles square, producing about half an inch of snow cover. It's hard to say whether airports would rather have snow or fog, but someday they might get to make that choice.

Thanks today to writer Bob Henson. The Weather Notebook is underwritten by Subaru of America and the National Science foundation and is a production of the Mount Washington Observatory.