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Name: Ruby
Status: student
Grade: 4-5
Location: CA
Country: N/A
Date: 1/9/2006

Why doesn't water from the ocean fall as salty rain?

Ruby, Actually, much of the rain that falls near a coastline has salt in it. Salt is an excellent nucleus for water vapor to form a rain drop on. However, since a lot of water is contained in a raindrop, it dilutes the salt nucleus to the point that it's hard to tell that there is salt in the drop. The rain drop is not nearly as salty as seawater.

David R. Cook
Climate Research Section
Environmental Science Division
Argonne National Laboratory

Dear Ruby-

When water evaporates from the oceans, the salt is left behind. There are lots of microscopic salt particles in the atmosphere however, as water droplets from waves evaporate. These same salt particles become condensation nuclei for raindrops and snowflakes. The salt quantity in the raindrops is so small that the raindrops are considered fresh water. There are other kinds of condensation nuclei besides salt particles, such as dust, volcanic ash, even ice crystals, and other chemical particles that attract water vapor.

Wendell Bechtold, meteorologist
Forecaster, National Weather Service, Retired
Weather Forecast Office, St. Louis, MO

The salt dissolved in ocean water does not exist in the vapor, so only water evaporates, in a calm ocean. Now if the turbulence is great enough, caused by winds and waves some salty water does get "splashed" into the air and will be incorporated into rain, but this is a small effect compared to the vaporization of pure water from ocean water.

Vince Calder

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