After a gap of 53 years, Delhi conducted cloud seeding trials on Tuesday to induce artificial rain in the national capital amid surging pollution levels, even as the weather department did not record any traces of rainfall in the city.
The Delhi government, in collaboration with IIT-Kanpur, conducted the trials in parts of Delhi, including Burari, north Karol Bagh, Mayur Vihar, and Badli, with more such exercises planned over the next few days, Environment Minister Manjinder Singh Sirsa said.
Later, in the evening, the government in a report said that the cloud seeding trials helped in reduction of particulate matter at locations where the exercise was carried out even as conditions were not ideal for it. The report said that two precipitation events were recorded — Noida at 4 pm (0.1 mm of rain) and Greater Noida at 4 pm (0.2 mm).
"Before cloud seeding, the PM 2.5 level was 221, 230, and 229 in Mayur Vihar, Karol Bagh, and Burari, respectively, which reduced to 207, 206, and 203, respectively, after the first seeding. Similarly, PM 10 level was 207, 206, 209, which got reduced to 177, 163, 177 at Mayur Vihar, Karol Bagh, and Burari, respectively," said the report.
The government said that the moisture content predicted by the India Meteorological Department (IMD) and other agencies remained low at 10–15 per cent, which is not an ideal condition for cloud seeding.
Environmentalists termed the cloud-seeding trial a short-term measure, saying it may temporarily reduce pollution but fails to address the root causes of the capital's deteriorating air quality. The opposition AAP mocked the exercise, calling it a tactic to "steal Lord Indra's (rain god's) credit," even as the BJP hailed the move to tackle the pollution crisis.
The first trial was completed by 2 pm on Tuesday, and for the second trial, the flight took off from Meerut around 4 pm and completed the trial in an hour. Soon after the first trial, Sirsa said IIT-Kanpur has opined that rain could happen within 15 minutes to four hours after the exercise. "However, the rainfall won't be heavy since the humidity levels were only at 15 to 20 per cent," the minister said.
However, the IMD data shows there was no rainfall recorded in Delhi till late evening.
Detailing how the exercise was carried out, Sirsa said the Cessna aircraft took off from Kanpur, adding it released eight fire flares each weighing 2 to 2.5 kilograms, and the trial lasted for half an hour. Each flare lasted for two to two-and-a-half minutes, he said. "The clouds had a humidity of 15 to 20 per cent. The flares were released for 17 to 18 minutes," Sirsa said.
According to officials, during the trial, silver iodide and sodium chloride compounds were released from the aircraft to induce artificial rain. They said the expected timeline for rainfall ranges from 15 minutes to 24 hours, depending on weather conditions, and there can be rain later in the night.
The second trial was also conducted later in the day in outer Delhi and covered areas like Badli. Eight flares were fired during the exercise. Nine to 10 such trials are planned over the next few days, Sirsa said, adding that since the IMD has informed that the wind direction is towards north, areas falling under that region are being targeted.
"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 a first such scientific step in India to reduce pollution," he added.
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 little north of Burari. The first round involved six flares released at an altitude of nearly 4,000 feet above ground level, with a burn duration of eighteen-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, Sirsa, in a post on X, said the 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 under the leadership of Chief Minister Rekha Gupta," he added.
The trial, aimed at inducing artificial rain, is part of the Delhi government's broader strategy to mitigate deteriorating air quality during the winter months. The government had conducted a test flight over Burari last week. 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.
Historically, the first cloud seeding trial in the national capital was conducted during the monsoon of 1957, while the second attempt was made during the winter of the early 1970s, according to climate scientist Roxy Mathew Koll from the Indian Institute of Tropical Meteorology (IITM). In 1972, silver iodide particles released from ground-based generators acted as tiny nuclei around which moisture condensed to form raindrops, according to an IITM report.
As the Delhi government conducted the exercise on Tuesday, environmentalist Vimlendu Jha called the move a "temporary", "end-of-the-tail" solution that might provide relief for a few days. He advised the government to focus on tackling pollution at the grassroots level.
"Cloud seeding also affects soil and water bodies as chemicals like sulphur and iodide are injected into clouds. Moreover, this approach is city-specific, what about the pollutants coming from neighbouring states?" he asked.
Meanwhile, Delhi's air quality showed a marginal improvement with an AQI of 294 ('poor' category) as against 301 ('very poor') recorded the previous day.
