Cloud Seeding

Why in News

Delhi govt plans ‘cloud seeding’ to induce rains amid pollution in Delhi.

Important Points

About cloud formation

• Comprised of minuscule water droplets or ice crystals.
• Form when atmospheric water vapor cools and condenses around particles like dust or salt.
• Water droplets or ice crystals require condensation or ice nuclei.
• Without these particles, precipitation in the form of raindrops or snowflakes cannot occur.

Cloud Seeding

• Cloud seeding is an artificial method used to increase rainfall by introducing certain substances into clouds.
• During cloud seeding, chemicals like silver iodide, potassium iodide, and dry ice are released into the sky using airplanes and helicopters.
• These chemicals attract water vapour, leading to the formation of rain clouds.
• It usually takes about half an hour for this method to make it rain.

Techniques of cloud Seeding:

1. Hygroscopic cloud seeding aims to accelerate the coalescence of droplets in liquid clouds, resulting in the formation of larger droplets that lead to precipitation.

• The seeding agents used in hygroscopic cloud seeding serve as efficient cloud condensation nuclei (CCN) or GCCN and play a crucial role in strengthening the condensation and collision–coalescence process, thereby widening the droplet size distribution (DSD) and increasing the precipitation efficiency.

2. Glaciogenic cloud seeding, focuses on inducing ice production in supercooled clouds, leading to precipitation.

• Glaciogenic cloud seeding involves dispersing efficient ice nuclei, such as silver iodide particles or dry ice, into the cloud, which enhances ice particle production and increases rain.

Utility of Cloud Seeding

That serves various purposes, including:

• Reducing the impact of droughts
• Preventing forest fires
• Increasing precipitation
• Enhancing air quality.

Cloud Seeding's Effectiveness:

• Cloud seeding is proven effective for enhancing rainfall under suitable conditions.
• A random seeding experiment selected 276 convective clouds, with 150 clouds subjected to seeding and 122 unseeded.
• Specific cloud characteristics, including liquid water content and vertical motion, were used to identify clouds with potential for rainfall.
• Targeted convective clouds were typically over one kilometer deep and likely to evolve into deep cumulus clouds.

Success story of cloud seeding

• A cloud seeding experiment carried out in Solapur city, which falls on the leeward side of the Western Ghats and hence gets low rainfall, was able to achieve 18% relative enhancement in rainfall.

Applications:

• Cloud seeding is done to enhance winter snowfall and increase mountain snowpack, which can supplement the natural water supply for communities in the surrounding area.
• Cloud seeding can also be done to prevent hailstorms, dissipate fog, induce rainfall in drought-prone regions, or reduce air pollution.

Challenges:

• Cloud seeding requires the presence of moisture-filled clouds, which are not always available or predictable.
• Cloud seeding does not occur during times when additional precipitation would be problematic, such as times of high flood risk or busy holiday travel periods.
• Cloud seeding may have negative effects on the environment and health, such as altering the natural water cycle, contaminating the soil and water with chemicals, or affecting the local climate.