Dear Tom,
A lot of Chicago’s moisture comes from the saltwater Gulf of Mexico, so why isn’t our rain salty?
Bob Johnson, Oak Park
Dear Bob,
Since the beginning of time, the saltwater oceans have been the reservoir of about 97 percent of this planet’s water supply. The water is constantly being recycled, evaporating into the atmosphere and returning to Earth as rain or snow in an ongoing hydrologic cycle. Sea water is indeed salty, with about 35,000 parts of salt per million parts of water. However, the salt in sea water is only dissolved in it and not chemically bonded, so it is left behind when the water evaporates, like when a pot of saltwater is boiled dry on a stove. That is the reason sea air is salty when the ocean’s spray evaporates, and also why precipitation falls as fresh water.
When salty ocean water surges inland as in a hurricane storm surge, it can kill vegetation.
———-
Write to: ASK TOM WHY, 2501 Bradley Pl., Chicago, IL 60618 or: asktomwhy@wgntv.com
Weather Report is prepared by the WGN-TV Weather Center, where Tom Skilling is chief meteorologist. His forecasts can be seen Monday through Friday on WGN News at noon, 5:55 p.m. and 9 p.m.
WGN-TV meteorologists Steve Kahn, Richard Koeneman and Paul Dailey plus weather producer Bill Snyder contribute to this page.
IN THE WEB EDITION: For updated weather news, forecasts by ZIP code and local radar images, go to chicagotribune.com/weather or wgntv.com
