Delhi's AQI Drops But Remains 'Severe'; Can Artificial Rain Be the Silver Lining?

The air quality index (AQI) on Wednesday has come down from “severe plus” category on Tuesday to “severe” on November 20, according to the central pollution control board (CPCB). Meanwhile, the Delhi environment minister Gopal Rai has requested the union government to give clearance for allowing artificial rain in the national capital to ease the alarming air pollution levels. In the letter addressed to the union environment minister Bhupender Yadav on November 19, Rai has asked the central government to hold a meeting with experts from IIT Kanpur and the Union government agencies in drawing a roadmap to deal with increasing air quality index (AQI) levels in Delhi-NCR. 

“We are consulting specialists to explore measures to reduce the smog. One of the solutions under consideration is artificial rain, which can help settle pollutants and clear the air,” Rai said in a press conference on Tuesday. 

“People are finding it difficult to breath. It is disappointing that we received no response over the first letter we wrote to the union environment minister...,” the Delhi environment minister told PTI. 

The air quality mark has reached stage four with AQI ranging above 450, which is considered most dangerous and is categorised as “severe-plus”.  

What is artificial rain? 

Artificial rain is an induced way of cloud seeding. For artificial rain to take place, meteorologists first identify clouds that are suitable for seeding and have sufficient moisture to produce significant precipitation on their own. 

When the moisture laden clouds are injected with salts like silver iodide, potassium iodide, or sodium chloride, it is called seeding. Then lanes equipped with burners fly through or above the seeded clouds and following this the agents act as a nucleus around which water droplets can form. Consequently, they become heavy leading to rainfall. 

“Seeding accelerates cloud microphysical processes. You need sufficiently large droplets that can reach the surface of the Earth and not evaporate on the way,” Sachchida Nand Tripathi told the Indian Express. Tripathi is a Professor at IIT Kanpur and steering committee member, national clean air programme. 

While experts have said artificial rain is not a long-term solution, it might offer a short-term relief.