Rabu, 31 Agustus 2011

Lasers Could Create Clouds and Rain, on Demand

Weather control freaks may get their next rainmaking tool in the form of an infrared laser. Scientists have successfully created small clouds by firing a laser both inside a lab and under the autumn skies of Berlin, Germany, New Scientist reports.

The concept works because laser pulses strip electrons from atoms in the air and promote formation of hydroxyl radicals. Those in turn make sulfur and nitrogen dioxides into particles which can form the basis for water droplets -- not unlike how current cloud seeding methods use silver iodide crystals as the "seeds" for water droplets.

But rather than seeding the air with crystals delivered by airplanes or artillery rockets, the Swiss, German and French researchers used a laser which could generate 220-millijoule pulses within 60 femtoseconds, where one femtosecond is one millionth of one billionth of a second. That's as much power as what 1,000 power plants could generate, according to Jérôme Kasparian at the University of Geneva, Switzerland.
A lab experiment involved the laser firing inside water-saturated air to create tiny clouds similar to airplane contrails. The outdoor experiment did not produce visible clouds, but clearly boosted the density and size of water droplets according to weather LIDAR measurements.

Cloud seeding has had plenty of critics voice their doubts over its effectiveness. Still, China has used the weather-control tactic for its hosted Olympics, and even delivered snowstorms to weary Beijing residents on multiple occasions. Russia has also prominently used cloud seeding in an attempt to make snow fall on the outskirts of Moscow rather than on the city itself.

Nations intrigued by the idea of more high-tech cloud seeding shouldn't abandon their silver iodide just yet. Researchers need to work on tuning their laser in the hopes of creating large enough water droplets which could fall as rain.

 by "environment clean generations"

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