What is cloud seeding?
CLOUDS are made up of tiny water droplets or ice crystals that form when water vapour in the atmosphere cools and condenses around a tiny particle of dust or salt floating in the atmosphere.
Without these particles, known as cloud condensation nuclei, raindrops cannot form and precipitation will not occur.
Cloud seeding is a weather modification technique that improves a cloud’s ability to produce rain by introducing tiny ice nuclei into certain types of subfreezing clouds.
These nuclei provide a base for rain to form.
Cloud seeding is usually carried out by sprinkling particles from a plane. Using weather forecasting techniques, suitable clouds are identified based on the location of the target area and the prevailing winds.
Given the appropriate conditions, cloud seeding can modify clouds and induce rain. This works in two ways — by producing rain when none would fall naturally; or by increasing the amount of rain that falls over a particular area.
It is crucial to note that cloud seeding requires existing clouds, it will not produce rain out of thin air.
Also, not all clouds create rain. Even if they do make rainwater, only a few clouds are able to produce enough moisture that allows for large raindrops.
This may happen because there aren’t enough ice particles within a cloud. Because of this, there aren’t enough cloud droplets to combine and make raindrops.
Another reason that certain rain clouds may struggle to make rain is that some don’t last long enough to have cloud droplets gather to create rain.
Cloud seeding gives these clouds a lot more ice crystals (or cloud nuclei). If experts complete seeding at the right time, it leads to more moisture supply, which will eventually create rainwater.
Experts use silver iodide because its structure is very similar to natural ice crystals.
When they put silver iodide in the top part of a growing cloud, the silver iodide crystal grows quickly once exposed to the cloud’s moisture.
Right after, the ice crystal becomes a heavy, large raindrop. It will then fall through the cloud and onto the ground as rain.
Just 1 gram of silver iodide can create up to 10 trillion artificial ice crystals.
How they cloud seed
Cloud seeding can be done from ground-based generators or aircraft.
Most cloud seeding operations use a compound called silver iodide to aid in the formation of raindrops.
Silver iodide exists naturally in the environment at low concentrations, and is not known to be harmful to humans or wildlife.
When storm systems move through cloud seeding project areas, a solution containing a small amount of silver iodide is burned from ground-based generators or released from aircraft.
Upon reaching the cloud, the silver iodide acts as an rain forming nuclei to aid in the production of rain.
The team of experts who conduct cloud seeding include meteorologists who monitor the weather throughout the season for appropriate cloud seeding conditions.
Cloud seeding does not occur during times when additional precipitation would be problematic, such as times of high flood risk.
Benefits of cloud seeding
Cloud seeding is used all over the world as a method for enhancing rainfall, thereby supplementing the natural water supply available to communities of the surrounding area.
The effectiveness of cloud seeding differs from project to project, but longterm cloud seeding projects have been shown to increase the overall rainfall received.