What is Cloud Seeding? How Artificial Rain Helps Combat High AQI Levels

What is Cloud Seeding: As the capital suffers unprecedented pollution levels, the government of Delhi on Tuesday has advocated for ‘cloud-seeding’ or ‘artificial rainfall’ as a short term measure aimed at reducing pollution levels. Delhi environment minister Gopal Rai urged the Centre to convene an emergency meeting to discuss the matter and sanction the proposal of cloud-bursting the city.

A more or less the same suggestion was put forward in the preceding November, but the plan was aborted on account of adverse climatic conditions.

The Delhi government on its part had earlier stated that it shall bear all the costs for the experiment. The plan, which was structured to roll out in three stages was said to cost about one crore rupees for every one hundred square kilometers. The first phase was to extend up to three hundred square kilometers for three crores and the second phase was to cover the area extending one thousand square kilometers for ten crores depending on the outcome of the first phase.

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What is cloud seeding?

Cloud seeding is the practice of adding certain [AgI] ice nucleus forming materials (silver iodide) into the clouds with an intention of inducing the rainfall from the clouds. Clouds can be seeded to make it rain by enhancing the ice nuclei present within the clouds by using silver iodide.

In the case of cloud-seeding these elements are squirted in the sky through light aircrafts and helicopters to make it rain. These served the purpose of condensation of water vapor and the formation of rain clouds. Most often this process takes roughly 30 minutes to result in rain.

This technique can also be described in two ways. According to ScienceDirect, there are two categories of cloud-seeding.

Hygroscopic Cloud Seeding: This method promotes precipitation from existing liquid clouds by facilitating the coalescence of smaller drops into larger ones. Salt particles are typically emitted at the base of the cloud.

Glaciogenic Cloud Seeding: This technique promotes the generation of ice in supercooled clouds by releasing efficient ice nucleation agents such as silver iodide or dry ice, thereby enhancing ice nucleation and consequent precipitation.

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Where was it used previously?

In India, cloud-seeding has not been adopted yet as an air quality improvement technique. While IIT Kanpur had a proposed experiment last year, it has been doing test runs along the Western Ghats since 2018, but the results in improving air quality have not been measured.

In December 2023, Lahore, Pakistan witnessed cloud-seeding after which the city’s AQI improved from 300, categorized as “poor”, after the seeding to 189, which is categorized as “moderate”. The weather did however deteriorate again after a span of two days.

Not a practical solution?

Scientists and experts further disregarded tsunamis artificial rain initiative as ‘irrational’, arguing that there is no guarantee that it will work.

They said that Delhi’s winter pollution problem is not solvable with artificial rain, and that further studies needs to be done. “Until we have enough data or research to prove its effectiveness, this could be a waste of funds. Additionally, the environmental impact of silver iodide needs to be studied before considering its use,” said Mukesh Khare, an air pollution expert from IIT Delhi.

Sachin Ghude from the Pune based Indian Institute of Tropical Meteorology which undertook cloud seeding trials in the Western Ghats between the years 2015 and 2018 mentions that all clouds are not conducive for seeding.  “We need sufficient clouds, particularly convective clouds. Over the past week, clouds have been scarce. Our tests also showed that even when clouds are present, not all of them will lead to rainfall,” he said.

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