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Flying rain dance.


Not far from the border of Texas, Dan Breed thinks he can make it rain. A meteorologist at the National Center for Atmospheric Research The National Center for Atmospheric Research (NCAR) is a non-governmental U.S.-based institute whose stated mission is "exploring and understanding our atmosphere and its interactions with the Sun, the oceans, the biosphere, and human society.  (NCAR NCAR National Center for Atmospheric Research (USA)
NCAR North Carolina Association of Realtors
NCAR National Conference on the Advancement of Research
NCAR Navy Center for Acquisition Research
NCAR NorCal Aussie Rescue
), Breed is sending airplanes into clouds 10,000 feet above Earth's surface Noun 1. Earth's surface - the outermost level of the land or sea; "earthquakes originate far below the surface"; "three quarters of the Earth's surface is covered by water"
surface
, and setting off fireworks fireworks: see pyrotechnics.
fireworks

Explosives or combustibles used for display. Of ancient Chinese origin, fireworks evidently developed out of military rockets and explosive missiles and accompanied the spread of military explosives westward to
 in hopes of getting water to the thirsty fields below.

Clouds are made of water droplets. Normal rainstorms occur when the water droplets collide and stick to one another. The small droplets combine to form heavier drops. The heaviest drops fall to Earth as rain. But the rain won't fall if the clouds evaporate before the drops have a chance to collide.

Scientists have tried for years to "seed" clouds to make them release their moisture. They shoot silver iodide silver iodide
n.
A pale yellow, odorless, tasteless powder that darkens when exposed to light and that is used as an antiseptic.
 particles into the clouds. The particles act as "seeds" around which ice crystals form. When they get heavy enough, the crystals fall to the ground as snow and hail.

But seeding for rain that way doesn't work well in warm climates. So, with the help of the Mexican government, NCAR's Dan Breed is trying a new approach.

First a radar instrument on the ground bounces radio waves Radio waves
Electromagnetic energy of the frequency range corresponding to that used in radio communications, usually 10,000 cycles per second to 300 billion cycles per second.
 off the cloud. That helps scientists measure the cloud's distance from Earth, as well as how fast and in which direction the cloud is moving. With the radar's guidance, an airplane with burning flares on its wings flies just below the cloud.

The flares are like emergency road flares, except they release salt as they burn. As the salty smoke floats into the clouds, the salt attracts water. That causes the cloud droplets to clump together. With this new technique, says Breed, up to 60 percent of the cloud's water falls to the ground.

Don't expect this flaming rain dance to prevent droughts, however. "It's not a magic bullet (jargon) magic bullet - (Or "silver bullet" from vampire legends) A term widely used in software engineering for a supposed quick, simple cure for some problem. E.g. "There's no silver bullet for this problem". ," Breed explains. "Drought periods are the worst time to do this." In a drought, with practically no water around, there are no clouds to seed.

But when rain is unpredictable, and clouds are plentiful, the flames in the sky could keep the water flowing -- and the crops growing -- here on Earth.
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Title Annotation:using radar and airplanes with burning flares on their wings to seed clouds for rain
Author:Goldstein, Debra
Publication:Science World
Article Type:Brief Article
Date:Mar 21, 1997
Words:348
Previous Article:Fire & ice. (methane hydrate, made of natural-gas molecules trapped in ice)(Brief Article)
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