Imagine a world where drought-ridden areas can get the rain they need, on demand. A place where airports can eliminate dangerous fog that could potentially lock thousands of passengers on land and compromise the safety of those in the air. Think about having the ability to reduce the size of hail during thunderstorms, especially in areas that see frozen pellets the size of softballs wreak havoc on homes and property.
Although these scenarios sound like something out of a science fiction movie, weather modification isn’t just a far-fetched idea that is only seen on-screen: weather experts have done it for years.
In 1946, General Electric researcher Bernard Vonnegut (older brother of Kurt, the science fiction writer) discovered that silver iodide contained properties that could alter the weather. Ever since, scientists and weather experts have tried to use the weather modification technique to bring rain to dry areas.
Although some claim that cloud seeding is quite effective, others aren’t confident in what it can do, or if it is even safe. But there’s one thing about cloud seeding that is for certain: the prospect of rain has people around the world wanting to try it out.
Clouds and Rain 101
In order to fully understand cloud seeding, it helps to know the basics of clouds and rain.
Clouds are formed when condensed water vapor clings to tiny dust particles called condensation nuclei, which are found floating around the atmosphere. Trillions of these powerful duos come together and create the wispy, fluffy, and sometimes menacing clouds you see hanging out in the sky.
If too much water condenses around a particle or if the air temperature drops, these water droplets return to Earth’s surface in the form of rain. Frozen particles come down as snow. When an updraft causes rain to ascend to a higher, colder altitude, the particles freeze then descend as hailstones.
Just add ice.
Cloud seeding is basically science’s way of giving Mother Nature a little kick in the pants.
According to the North American Weather Modification Council, cloud seeding increases a cloud’s chances of producing precipitation. This is done by essentially impregnating a cloud with small particles that encourage clouds to produce rain by acting on something called supercooled water.
“Supercooled water is water that is actually below 32 degrees, but is still in liquid form,” says Tony Pann, a meteorologist for WBAL-TV in Baltimore. “This is common in clouds at higher latitudes. This water freezes around small particles suspended in the air to form the ice crystals that make up the top of most clouds. Cloud seeding is an attempt to accelerate this process by adding condensation nuclei into clouds, in hopes of creating more precipitation.”
The ice nuclei help the supercooled liquid water to freeze at higher temperatures than it would naturally. This speeds up the precipitation process and helps the cloud use up its water more efficiently. The result is rain or snow that may not have happened otherwise.
Make it rain.
So, what makes all this cloud magic happen? Typically, two types of seeding techniques are used to encourage clouds to get their precipitation on, and the type that is used depends on the temperature of the cloud.
Meteorologists and scientists use two different processes to develop the precipitation. The “cold rain” process uses ice crystals to encourage the rain and snow, while the “warm rain” option uses salt to get the desired results.
In cold rain situations, silver iodide is used to inspire clouds to produce moisture, as well as dry ice, or frozen carbon dioxide. Silver iodide, however, is typically used most often because of how well ice binds to it. Likely, it is because ice and the inorganic compound share a similar molecular structure. The material is often placed into flares that are then either flown or shot into the clouds. Trillions of microscopic-sized silver iodide particles, or ice nuclei, are then formed and increase the chances of ice crystals forming in the cloud.
Dry ice cools the air down so quickly that either unfrozen cloud droplets freeze or water vapor molecules become so cold that they fuse together and cause very small ice crystals to form. The result is often moisture that falls as snowflakes or raindrops.
Warm rain techniques are used in hotter climates. Again, flares are used to penetrate the clouds, but this time they are filled with some type of salt, commonly calcium chloride. This salt will attract water vapor to form droplets. Eventually, the water droplets come together. When they become too heavy to stay in the air, they fall down as raindrops.
Is it effective?
Having control of the weather provides great opportunities for areas of the world that are in need of moisture. If cloud seeding is actually effective, it could mean the end of drought and all of the problems that come with it. Although this sounds good in theory, in practice, it may be impossible.
A couple of problems could potentially hold back this promising idea. First, cloud seeding only works if clouds are present. Clouds are often scarce in times of drought. The best time to engage in cloud seeding is when precipitation levels are average or higher than normal, as you’ll have access to clouds. Waiting until a drought situation to attempt cloud seeding is often too late.
Secondly, cloud seeding may not have the capabilities to treat an expansive space.
“There has been some evidence that cloud seeding works, but it's very difficult to do this on a large enough scale to matter, and it's unlikely that cloud seeding can be done on a large enough scale to help in drought-stricken areas,” Pann tells Urbo.
Is cloud seeding safe?
The idea of cloud seeding certainly raises a few eyebrows. Some argue that it is unnatural and worry that it could cause damage to the weather system and patterns.
“Environmental manipulation, of any kind, is very complex and the long-range implications are hard to predict,” says Pann.
However, using cloud seeding to manipulate the conditions inside of one cloud (or group of clouds) most likely won’t change an entire weather system, according to the North American Weather Modification Council. Weather patterns are made depending on large-scale atmospheric conditions, most likely not because of what is happening within one cluster of clouds.
Who's cloud seeding now?
The potential of creating rain and snow in areas that are in need of moisture is too good for most to pass up. Countries across the globe are testing out their techniques to see if they can create water on demand.
In August 2017, the Indian state of Karnataka tried its hand at cloud seeding in an attempt to bring some moisture to the area, which is in its third year of drought.
Using the warm rain technique, planes planned to spray sodium and potassium chloride and silver iodide into the clouds for 60 days, with the hopes that they will attract water droplets that will bond together to create rain. The goal at time of publishing was to increase precipitation in those areas by 15 to 20 percent.
China is a pro at making it rain and has been modifying its weather system for almost a decade.
In an effort to add moisture to its usually dry northwestern region between Xinjiang and Inner Mongolia, China has had much success with weather modification and is the major player in the cloud seeding game right now.
In fact, China is so confident in its weather modification capabilities that in June 2017, it announced it was investing 1.5 billion yuan ($168 million) into a three-year cloud seeding program. The country hopes that the program will result in a rise in precipitation over an area of over 370,000 square miles.
The massive amount of money that China is pouring into the project will be used to purchase four new planes used for cloud seeding and make updates to eight existing planes. It will also cover the cost of 900 rocket launch systems and more than 1,800 digital control devices.
Producing precipitation isn’t the only reason for China’s weather manipulation. During the 2008 Beijing Olympics, the country actually eliminated the threat of rain so that the games could be played under clear skies. China also uses modification techniques to lower blistering heat and reduce the amount of smog in the air.
During a four-year drought in Southern California in 2016, cloud seeding was used to bulk up the amount of rainfall the area would see.
By lacing clouds with silver iodide, North American Weather Consultants, a group contracted by Los Angeles County to supply cloud seeding services, attempted to produce rain for the dry region.
The LA County Department of Public Works believes that cloud seeding will bring an extra 1.5 billion gallons of water to the parched area each year.
Some LA residents, however, have raised suspicions of a government conspiracy:
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The Final Word
The bottom line when it comes to cloud seeding is yes, it probably works. However, it typically only provides results when used in smaller scales. And because it can only work when clouds exist, cloud seeding cannot bring a region out of a drought once the drought has set in.
When it is used during times of ideal precipitation, however, it may be effective and can provide water that can be stored and used when needed.