Dear Tom,
Since hurricanes develop over oceans, does any of the rain come down as salt water?
— John
Dear John,
A raindrop is pure water (with the exception of the condensation nucleus around which it initially formed and any pollutants it might have picked up from the atmosphere). Rainwater is pure because materials such as salt dissolved in ocean water remain behind when water evaporates from the ocean surface, and that’s fortunate because seawater contains a great deal of salt.
Herbert Swenson of the U.S. Geological Survey tells us ocean water contains about 35 pounds of salt per 1,000 pounds of water. One inch of rain across Chicago yields 33.1 billion pounds of water. If rainwater contained salt at the concentration of ocean water, 1.2 billion pounds of salt would accompany every 1-inch rain across the city.
———-
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
