Firing laser beams into the sky could make it rain, say scientists

Water droplets have been created by shooting lasers into the air. The technique might be used to create or prevent rain

Ever since ancient farmers called on the gods to send rain to save their harvests, humans have longed to have the weather at their command.

That dream has now received a boost after researchers used a powerful laser to produce water droplets in the air, a step that could ultimately help trigger rainfall.

While nothing can produce a downpour from dry air, the technique, called laser-assisted water condensation, might allow some control over where and when rain falls if the atmosphere is sufficiently humid.

Researchers demonstrated the technique in field tests after hauling a mobile laser laboratory the size of a small garage to the banks of the Rhône near lake Geneva in Switzerland.

Records from 133 hours of firings revealed that intense pulses of laser light created nitric acid particles in the air that behaved like atmospheric glue, binding water molecules together into droplets and preventing them from re-evaporating.

Within seconds, these grew into stable drops a few thousandths of a millimetre in diameter: too small to fall as rain, but large enough to encourage the scientists to press on with the work.

…With improvements, shooting lasers into the sky could either help trigger or prevent showers. One possibility might be to create water droplets in air masses drifting towards mountains. The air would cool as it rose over these, causing the water droplets to grow and eventually fall.

An alternative might be to stave off an immediate downpour by creating so many tiny droplets in the air that none grew large enough to fall. “Maybe one day this could be a way to attenuate the monsoon or reduce flooding in certain areas,” Kasparian said. …

via Firing laser beams into the sky could make it rain, say scientists | Science | The Guardian.