Cloud Seeding

• Context (TH | TOI): Cloud seeding experiment in Solapur of Maharashtra resulted in 18% more rainfall than normal conditions.

• Solapur falls on the leeward side of the Western Ghats and hence normally gets low rainfall.
• Cloud seeding is a weather modification technology that artificially stimulates rainfall by spraying chemical substances into the air that serve as cloud condensation nuclei.
• Cloud condensation nuclei are small particles upon which water vapour condenses to form clouds.
• The chemical substances used are silver iodides, potassium iodides, dry ice (solid carbon dioxide) or liquid propane.
• It works only when there are enough pre-existing clouds in the atmosphere.

Different Cloud Seeding Methods

• Hygroscopic Cloud Seeding: Salts are sprayed through explosives in the lower portions of clouds.
• Static Cloud Seeding: Chemicals like silver iodide crystals are sprayed into clouds.
• Dynamic Cloud Seeding: Vertical air currents are boosted to encourage more water to pass through the clouds which translates into more rain.

In the Solapur experiment, hygroscopic cloud seeding was used and calcium chloride flare was used for seeding the clouds.

Applications of Cloud Seeding

• Increases rainfall
• Regulates weather: Creates favourable microclimates by dispersing fog, suppressing hail, and modifying cyclones.
• Controls air pollution and water pollution

Limitations of Cloud Seeding

• Cannot mitigate drought: It can simply partially address the water requirements.
• Cannot produce rainfall from all clouds.

Challenges in Cloud Seeding

• Cause abnormal weather conditions: For e.g., when naturally less moisture place receives more rainfall, then it may cause flash floods.
• Harmful for environment and health: Chemicals used in cloud seeding are toxic.
• Contribute to global warming: The chemicals used in cloud seeding are a source of GHGs.