Cloud-seeding in Delhi: What It Is and How It Works

NEW DELHI: In a major planned initiative to mitigate pollution through artificial rains, the Delhi government, in collaboration with the IIT-Kanpur, on Tuesday conducted cloud-seeding trials in parts of the national capital. This was the second such trial conducted in Delhi; more such exercises are planned over the next few days.

Delhi environment minister Manjinder Singh Sirsa said, "A Cessna aircraft took off from Kanpur. It released eight fire flares, each weighing 2 to 2.5 kg, and the trial lasted for half-an-hour. Each flare lasted for two to two-and-a-half minutes. The clouds had a humidity of 15 to 20 per cent. The flares were released for 17 to 18 minutes."

"Nine to 10 such trials are planned over the next few days," Mr Sirsa said, adding that since IMD has informed us that the wind direction is towards north, areas falling under that region are being targeted.

According to Delhi government officials, the aircraft covered areas like Delhi's Burari, north Karol Bagh and Mayur Vihar before landing at the Meerut airfield.

Asserting that, according to expert forecasts, after cloud seeding, rain occurs anytime in 24 hours, depending on cloud moisture, Mr Sirsa said that initial weather radar readings and on-ground observations recorded light rainfall of 0.1–0.2 mm at the Delhi-Noida border around 4 pm.

The environment department said that the data from 20 selected monitoring sites across Delhi were captured, with a primary focus on AQI, PM2.5 and PM10. "Before the first seeding, PM2.5 at Mayur Vihar, Karol Bagh and Burari was 221, 230 and 229 µg/m³, which fell to 207, 206, and 203 µg/m³, respectively, after the operation. PM10 at the same sites dropped from 207, 206, and 209 µg/m³ to 177, 163, and 177 µg/m³ post seeding," the environment department of the Delhi government said.

"This is a huge step taken by the government to mitigate pollution. If trials are successful, we will prepare a long-term plan till February. We hope that if this is successful, it will be the first such scientific step in India to reduce pollution," Mr Sirsa said.

According to sources, IIT Kanpur successfully executed the operation over Delhi in a corridor measuring roughly 25 nautical miles in length and four nautical miles in width, with the largest distance covered between Khekra and north of Burari.

Out of two rounds of the cloud-seeding trials, the first round involved six flares released at an altitude of nearly 4,000 feet above ground level, with a burn duration of 18-and-a-half minutes. A second flight took off at 3.55 pm, deploying eight flares at a higher altitude of around 5,000-6,000 feet.

Following the second trial, Mr Sirsa, in a post on X, said a Cessna aircraft took off from Meerut airport for Delhi and released cloud seeding flares in different areas. The team from IIT-Kanpur has expressed hope for good results from these systematically conducted experiments, he said.

"Based on the success of these trials, cloud-seeding will be used extensively in Delhi for pollution control," he added.

The government had conducted a test flight over Burari last week. During the test run, small quantities of silver iodide and sodium chloride compounds used to trigger artificial rain were released from the aircraft. However, due to low atmospheric moisture of less than 20 per cent, as against the 50 per cent typically required for cloud seeding, rainfall could not be induced then.

The Delhi government signed a memorandum of understanding with IIT Kanpur on September 25 to carry out five cloud seeding trials, all of which are planned in northwest Delhi.