The recent advancements in cloud seeding technology have unlocked its potential for increasing rainfall in water-scarce regions and mitigating drought conditions. In a study published by the Indian Institute of Tropical Meteorology, Pune in the Bulletin of the American Meteorological Society, the beneficial aspects of cloud seeding have been thoroughly explored.
The CAIPEEX Phase-4 Investigation
The landmark two-year study, known as the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX phase-4), was conducted during the summer monsoons of 2018 and 2019 in Solapur, Maharashtra. The key objective of this project was to evaluate the effectiveness of hygroscopic seeding in deep convective clouds and establish a protocol for cloud seeding. To achieve this, researchers employed calcium chloride flares for seeding warm convective clouds at their growing stage, ensuring minimum dispersion of seed particles. Further, two aircraft were used to study cloud parameters and perform the seeding.
Efficacy of Cloud Seeding
Participation in the study led to the selection of 276 convective clouds for a random seeding experiment. Of these, 150 clouds were subjected to seeding while the others remained unseeded. Certain cloud characteristics, such as content of liquid water and vertical motion, were leveraged to identify clouds with rainfall potential. As a result, it was confirmed that cloud seeding effectively enhances rainfall under suitable conditions.
Cost-Benefit Analysis and Managing Drought Conditions
The cost of producing water through cloud seeding was found to be approximately 18 paisa per liter, which could drop by over half with indigenous seeding aircraft. While cloud seeding is not a complete solution for droughts, it can potentially increase rainfall by 18%, helping meet water needs. Coupling cloud seeding with catchment-scale projects could enhance drought management efforts.
Practical Applications and Microphysics of Clouds
Regions with low rainfall like Solapur, situated on the leeward side of the Western Ghats, stand to gain significantly from cloud seeding. Moreover, the study provided comprehensive protocols and technical guidance for conducting cloud seeding in India while concurrently examining the microphysics and characteristics of convective clouds conducive to enhancing rainfall.
Cloud Variability
The study found that not all cumulus clouds are receptive to cloud seeding; around 20-25% can produce rainfall if seeding is implemented correctly. Due to varied cloud microphysics, results fluctuate with cloud seeding.
About Convective Clouds
Convective clouds, also called cumuliform clouds, form when warm, humid air rises through cooler air in the atmosphere – a process known as convection. These clouds can be categorized into cumulus clouds and cumulonimbus clouds, the latter being associated with thunderstorms. Cirrocumulus clouds, characterized by their small, white, fluffy patches, are high-altitude clouds with a typical wavy or honeycomb-like pattern.
Understanding Cloud Seeding
Cloud seeding is a technique to artificially create rain by implanting clouds with particles like silver iodide crystals. Two forms of cloud seeding include static and dynamic, both involving the introduction of ice nuclei into clouds but differing in complexity and sequence of events. Hygroscopic cloud seeding involves spraying particles of hygroscopic materials such as salts into the base of warm clouds, enhancing the reflectivity and stability of clouds.
Applications and Challenges
Cloud seeding has applications ranging from enhancing winter snowfall to preventing hailstorms and dissipating fog. It aids in inducing rainfall in drought-prone regions, increasing mountain snowpack, reducing air pollution, and supplementing natural water supply for communities in the surrounding areas. Despite its benefits, cloud seeding also poses challenges including unpredictability and availability of moisture-filled clouds, limitations during high flood risk or busy travel periods, and potential negative effects on the environment and health.
