Artificial rain in Delhi! What is cloud seeding? Types, Methods of dispersion, Common agents – EXPLAINED
Delhi, the national capital of India, has started experiments with cloud seeding to normalise the increasing hazard of air pollution. Chief Minister Rekha Gupta-led Bharatiya Janata Party (BJP) government is having its fingers crossed. Hopefully, Delhiites will get a chance to breathe fresh air!
What is cloud seeding?
Cloud seeding is a process that modifies the weather. The aim is to introduce rainfall to mitigate hail, disperse fog, or reduce air pollution. Under this process, substances are introduced into the air that serve as cloud condensation or ice nuclei.
Common agents for cloud seeding
Common agents used for the process are silver iodide, potassium iodide, and dry ice. These are combined with hygroscopic materials, such as table salt, which is gaining popularity due to its ability to attract moisture.
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Types of cloud seeding
There are three main types – static, dynamic, and hygroscopic. These are categorized based on their target clouds and methods.
a) Static seeding: Static seeding involves introducing ice nuclei (like silver iodide or dry ice) into supercooled clouds (clouds with liquid water droplets below freezing). The ice nuclei trigger the formation of ice crystals (or snowflakes), which then increase in size and fall as precipitation.
Target cloud: Cold clouds
b) Hygroscopic seeding: Under hygroscopic seeding, fine salt particles (like calcium chloride) are sprayed into the base of warm clouds. The salt particles act as cloud condensation nuclei, attracting water and causing droplets to grow larger until they are heavy enough to fall as rain.
Target cloud: Warm clouds
Dynamic seeding: Dynamic seeding targets the vertical air currents (updrafts) within a cloud. In this process, a large number of seeding particles are introduced to stimulate the updrafts. This lifts more moisture up to the cloud, boosting the entire process. Here, there is a much larger volume of rain compared to static seeding.
Target cloud: Convective clouds
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Methods of dispersion
Methods of dispersion include aircraft, ground-based generators, and drones.
Which country first used artificial rain?
In 1946, the United States (US) was the first country to experiment with cloud seeding. America has a long history with the technology, with operations mainly concentrated in the western states to enhance snowfall and replenish water supplies.
In 1946, the first experiments were conducted by American chemist Vincent J. Schaefer. The location was the Berkshire Mountains of Massachusetts.
Presently, the USA continues to use artificial rain in states like Utah, Colorado, and California.
1947 – Project Cirrus
The first large-scale test was Project Cirrus in 1947. It was conducted by GE, the U.S. Army, and the U.S. Weather Bureau. Near the Bahamas, the team seeded a hurricane.