When you hear the word "drones" the first thing you might imagine an unmanned aircraft killing a Pakistani child or blowing up a Yemeni wedding party. But soon, drones may be a life-saving technology in California. They won't be launching missiles, but trying to increase rainfall.
And as California enters its tenth month under a state of emergency due to drought conditions, this could be just the thinking outside the box that the parched state desperately needs.
To understand why drones may soon be used to make it rain, you need to know a little bit about the science behind "cloud seeding." Much more scientifically sound than a glorified rain-dance, cloud seeding is rare in the world of weather modification in that there is more or less a scientific consensus that it works.
William Cotton, an expert on cloud physics and professor of atmospheric science at Colorado State University, says that the obstacles facing cloud seeding are more a matter of execution than scientific principles.
"There has been little controversy that if you can actually get the seeding material into the clouds it will enhance precipitation," Cotton told VICE News.
You can think of cloud seeding as a process of squeezing out a few extra drops from already existing clouds. By dispersing a silver iodide solution into clouds, scientists are able to encourage the formation of ice particles.
It turns out that the molecular structure of silver iodide is very similar to that of ice. So as the silver iodide passes through the clouds, water bonds to it like it would to ice. Because water droplets need to bond to something heavy - like ice or silver iodide - in order to precipitate, the end result is more precipitation.
The Desert Research Institute in Nevada (DRI) has been researching and implementing cloud seeding for 40 years. Widely considered the leaders in both the research and practice of cloud seeding, the institute claims its work can yield a 10 percent increase in precipitation. At their flagship operation at Lake Tahoe, with a $300,000 budget, they were able to generate an extra 6.6 billion gallons of water in the 2012-2013 winter.
"DRI has been doing this work for over 40 years in Nevada's watershed," Justin Broglio, a spokesman for DRI, told VICE News. "We pioneered the technique of trace chemical analysis that proved the effectiveness of cloud seeding."
By testing for silver in the eventual snowfall, DRI has been able to definitively show that there is indeed increased snowfall because of their efforts.
"By releasing the silver iodide solution into the cloud, we make the cloud more efficient at creating precipitation in the form of snow," Broglio said.
"Wintertime cloud seeding enhances the snowfall in the mountains and helps increase snowpack, which results in more spring runoff and water supply to surrounding watersheds."
In California, in particular, much of the state's water supply comes from melting snow in the state's mountainous north. So this work is particularly helpful for the Californian context.
"The strongest scientific evidence of cloud seeding increasing precipitation is in wintertime mountain cloud systems," concurs Cotton.
So far, DRI has conducted its cloud seeding operations with five land-based generators and a manned aircraft. With land-based generators, there are two options: put the generator in the valley or put it up in the mountains.
"A lot of time the generators in the valleys are not getting the seeding materials into the clouds," Cotton told VICE News. "But in a lot of places you can't get permission to build generators in the mountains because of wilderness reserves and tribal ownership."
Using airplanes to disperse the silver iodide solution overcomes many of these issues. Manned aircraft can fly into a more advantageous position directly above the clouds, but it's not a perfect solution. A pilot can't actually fly through storm-clouds or as close to cloud cover that is hugging mountaintops as is necessary for maximum efficiency.
And of course there is the ever-present issue of funding in a time when the federal government is decreasing budgets for the sciences across the board.
It's in this context that DRI set its eyes on drones as the answer. By outfitting unmanned aircraft with a mechanism to disperse the silver iodide solution, many of the issues facing both manned aircraft and land-based generators can be avoided.
"The main reasons we are looking toward the drone program is because it would be safer and less expensive," Broglio said. "Where a manned aircraft can't fly that close to mountaintops due to FAA regulations and safety precautions, a drone would be able to fly a lot closer to the mountain."
Nonetheless, there are a number of stumbling blocks before a drone cloud seeding program can be realized. DRI is still prototyping drone models, wrestling with how much weight the planes can carry, and testing methods for dispersing the solution.
Beyond these technical hitches, there are also legal and regulatory hurdles. While the FAA did approve DRI to run test flights in Nevada, it has yet to green-light an actual cloud seeding operation with drones.
"We have high expectations for the drone program and we are very excited to move forward with that application," says Broglio. "But right now it's still in the early development stages."
Follow Jay Cassano on Twitter: @jcassano