Cloud Seeding

Record-breaking rainfall in the UAE and Oman raised concerns about cloud seeding's role.

• Condensation: Water vapour condenses around small particles to form the droplets that make up a cloud. These droplets collide and grow; as they get heavy and the cloud gets saturated, it rains.
• Cloud Seeding Salts: With cloud seeding, clouds are usually injected with salts like silver iodide, potassium iodide, or sodium chloride, which is the ‘seed’. These salts are expected to provide additional nuclei around which more cloud droplets can form. They are dispersed into the cloud either using aircraft or through generators on the ground.
• Microphysical process: Seeding accelerates cloud microphysical processes, a sufficiently large droplets must be formed that can reach the surface of the earth and not evaporate on the way.
• Cloud condensation nuclei and ice nuclei: The substance that is dispersed into the cloud needs to have cloud condensation nuclei and ice nuclei and these two come from two different salts.
• Cloud droplets: The cloud condensation nuclei help form cloud droplets, and ice nuclei help to form ice crystals. Ice crystals grow faster than drops, and they become large and fall.

Cloud Seeding Methods

• There are three cloud seeding methods: static, dynamic and hygroscopic
• Static cloud seeding involves spreading a chemical like silver iodide into clouds. The silver iodide provides a crystal around which moisture can condense. The moisture is already present in the clouds, but silver iodide essentially makes rain clouds more effective at dispensing their water.
• Dynamic cloud seeding aims to boost vertical air currents, which encourages more water to pass through the clouds, translating into more rain. Up to 100 times more ice crystals are used in dynamic cloud seeding than in the static method. The process is considered more complex than static clouding seeding because it depends on a sequence of events working properly.
• Hygroscopic cloud seeding disperses salts through flares or explosives in the lower portions of clouds. The salts grow in size as water joins with them.