How to create rain clouds with lasers

Researchers have figured out a way to make rain from high-powered lasers.
Written by Boonsri Dickinson, Contributing Editor

I remember when I was in Australia a few years back, people complained that there was a severe shortage of rain. I had never heard water talked about so much in my life: Everything from radio programs to casual conversations revolved around the lack of rain.

Now the Aussies may have a solution for their drying woes. Researchers have figured out a way to use high-powered lasers to generate raindrops throughout parts of Berlin. But there is no need to carry umbrellas just yet because the researchers haven't exactly made anything resembling a torrential downpour.

However, the early results do look promising and using lasers to trigger condensation could one day be used to artificially induce showers — something that would be beneficial in drought-prone areas like Australia.

While optical physicist Jérôme Kasparian at the University of Geneva, Switzerland instincts to use a laser to make rain were right, creating rain on demand is a bit of an overstatement.

The lasers basically "squeeze" water from air, so water drops can form around the nuclei.

Trying to control rain patterns isn't new. People have been trying to pour silver iodide crystals on clouds so rain drops can form around it. However, it's unclear how "cloud seeding" actually works. And some are worried about how sprinkling chemicals all over the environment might be damaging.

This is how Kasparian made rain in the lab:

  • Used a high-powered laser in an atmospheric cloud chamber containing saturated air.
  • A low-powered laser was used to see and record any droplets that formed this way.
  • Short pulses of intense light shot a trillion watts of energy into the cloud chamber.
  • The drops were about 50 micrometers wide.
  • And just 3 seconds later, the drops grew to 80 micrometers. The smaller ones joined together.

To see how this would work in actual clouds, Kasparian used a high-powered Teramobile laser to create an electrical discharge. Although the method did create condensation when the humidity was high, going beyond that remains a major hurdle.

Kasparian told Nature: "We can only create condensation along the laser channel, so we won't be going out and making rain tomorrow."

If this laser technology can ultimately induce showers it could have major implications for the agricultural industry.

Back in 2005, a lot of farmers were suffering though. The Australian Bureau of Agriculture and Resource Economics predicted winter crop production would drop by 55 percent in the region I was in if rain didn't come. Some even thought a water war would breakout.

Fortunately, rain fell for weeks. If a laser could have done the trick, the drought-prone area would have been relieved much sooner.

But not everyone thinks that a laser will work. Rain is more complex than that. So many other conditions must be met before this laser technique produces the rain patterns many long for.

Top Image: J-P. Wolf/ University of Geneva (via Nature)

Bottom Image: NASA

This post was originally published on Smartplanet.com

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