Dear Tom,
Since much of our moisture comes from the saltwater Gulf of Mexico, why isn’t our rain salty?
Robert Panuncialman
Dear Robert,
Since the beginning of time, the oceans have been the reservoir for about 97 percent of this planet’s water supply. The water is constantly being recycled, evaporating into the atmosphere and returning to earth in the form of rain or snow in an ongoing hydrologic cycle.
The salt in sea water is only dissolved in it, not chemically bound and is left behind when the water evaporates, just as it is when a pot of salt water is boiled dry on a stove. That’s the reason that sea air is salty, when the ocean’s spray evaporates and also why precipitation falls to earth as fresh water.
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Tom Skilling is chief meteorologist at WGN-TV. His forecasts can be seen Monday through Friday on WGN News at noon and 9 p.m.
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