"Fog in a Bottle"
Fog is a cloud that forms just above the ground. It's spooky and neat. Really thick fog can reduce you to seeing only a few feet in front of you. It can be a real hazard to cars, planes and boats.
There are two kinds of fog, advection fog and radiation, or ground fog.
Advection fog is common along the pacific coast of the United States. Warm, moist air over the Pacific Ocean are blown inward. When that air moves over colder coastal waters, it cools quickly and fog forms. The fog is moved inland by the same westerly winds.
Advection fog plays an important role in the life of California Redwood trees. The Redwood trees have very shallow roots. They depend on water from sources other than water deep underground. What the trees do not get from rain, they get from the fog. Advection fog deposits moisture on the pine needles which then drips to the ground and is absorbed by the roots.
The other kind of fog is radiation, or ground fog. This fog is common lots of places. It forms when a layer of warm, moist air forms low to the ground. A layer of cooler, dry air forms overtop. As the ground cools, the warm, moist air is cooled quickly. As the air temperature lowers, small droplets of water condense, which we see as fog.
Radiation fog forms most often on cool, clear nights with a very slight breeze. It forms first in low valleys and spreads outward so long as conditions remain the same.
Make Your own Fog in a Bottle!
It's easy to simulate the formation of radiation fog. All you need are two bottles with a narrow enough neck that you can stick an ice cube into the mouth. Fill one bottle about half way with very hot water (it doesn't need to be boiling.) Fill the other bottle with about 1 inch of cold water.
After several minutes, pour out all the hot water but 1 inch. Now place an ice cube in the mouth of each bottle. Observe what happens in both bottles.
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Kathy Miles, Author, and Chuck Peters, Systems Administrator