by Emily Newton
As climate concerns have risen, mechanisms to mitigate and even control the weather have gained popularity. Cloud seeding is one of the most well-established and promising of these solutions. While the concept has been around since the mid-20th century, its recent adoption, evolution and urgency warrant a closer look.
How Does Cloud Seeding Work?
Cloud seeding is the process of managing precipitation by dispersing particulate matter into the clouds. The practice emerged in the 1940s, and at least nine states currently use it, mostly to promote rainfall in arid regions, though it can also theoretically suppress hail.
The specifics of the process vary depending on the technique, but it generally involves an aircraft that injects particles into existing clouds. These droplets attract water droplets, which condense around them until the saturation reaches a point where the cloud can no longer hold the liquid. Consequently, any additional moisture leads to rainfall.
This cycle of condensation and saturation mimics how rain naturally occurs. However, cloud seeding speeds the process by artificially introducing the particles necessary to accumulate water.
Current Cloud Seeding Methods
New technologies and additional research have led to the development of several distinct cloud seeding methods. Today, there are three primary mechanisms to facilitate this activity.
Static Seeding
Static cloud seeding is the most common technique. Here, an aircraft sprays a chemical solution — usually silver iodide — into the clouds. The planes typically fly through the middle or upper parts of the cloud and target warmer areas that already contain some moisture but aren’t cold enough for ice crystal formation. Because silver iodide’s structure is similar to ice, it fills that gap necessary for precipitation.
Silver iodide-based statics methods are the solution behind how China regulates Beijing’s rainfall and fights wildfires in mountainous regions. It gained popularity for its relative simplicity and applicability to a wide range of conditions, but researchers have debated its efficacy.
Dynamic Seeding
Dynamic methods are a more complex alternative. The method emerged in the 1990s and, like static mechanisms, disperses particulate matter into the top of a cloud. However, in addition to this seeding, it also attempts to drive and increase vertical air currents.
As more air flows upward through a cloud, it increases the amount of water that accumulates around the particles. Consequently, dynamic seeding can theoretically produce a larger precipitation event, but the added complexity means there are more opportunities for it to fail. Errors at any one of the multiple stages could stop it from achieving desired results.
Hygroscopic Seeding
A newer and growing alternative is hygroscopic cloud seeding. This technique is similar to static methods in that it requires little more than dispersing particles into existing clouds. Instead of spraying silver iodide through the top or middle, though, it releases salt into the lower portion of the cloud canopy through flares or explosives.
The key advantage here is that the salt crystals grow as they attract more water, leading to a compound effect of condensation. In warm areas, the particles will also travel upward through the cloud to maximize their dispersal. The United Arab Emirates (UAE) has turned to this method, as it’s 25 times cheaper than desalination, and it looks promising, although its long-term impact remains unclear.
Benefits of Cloud Seeding for Heavy Industries
Across all these methods, encouraging precipitation could have several benefits for industrial businesses. Increasing rainfall means facilities can collect more water from the rain to reduce their reliance on municipal pipelines or nearby freshwater sources.
Agriculture, in particular, stands to gain much from cloud seeding. Farms use roughly 70% of U.S. groundwater reserves, but the availability of these resources is becoming increasingly strained amid a growing population and changing climate. Additional rainfall could make up for it.
As the UAE’s efforts exemplify, seeding may also be more accessible than other methods to increase freshwater supplies. Desalinating oceans greatly increases resource availability but is prohibitively expensive. Local cloud seeding could lower costs while still maximizing supplies without taking away from drinking water.
Remaining Concerns
Despite these advantages, cloud seeding is not a perfect solution. While it has been available for decades, projects deploying it have been relatively scarce, especially on a large scale. Consequently, researchers are unsure of its broader impact on the environment, which, if negative, could counteract its sustainability.
The process’s effectiveness is also unclear. Seeding does promote rainfall, but it may only increase it by 10%, which may not be enough to offset demand for other freshwater sources. It also depends on existing clouds and moisture, so if an area is too arid, the practice will have little to no effect.
Cloud Seeding Is a Largely Untested but Promising Technology
It will likely take additional research and technological advancement to understand the long-term potential and side effects of cloud seeding. For now, it remains an intriguing, if uncertain, opportunity.
Farms and other facilities with high water demand may find seeding techniques to be beneficial, while organizations in drier areas may not. Any institution or company should look deeply into the available technologies and local weather conditions to determine if it’s worth the investment.
