Delhi cloud seeding fails to produce rain, but govt claims air quality improved

After a gap of 53 years, Delhi conducted cloud seeding trials on October 28 to induce artificial rain in the national capital amid surging pollution levels. Though it did not result in rain, Delhi recorded reduced pollution levels on Wednesday (October 29) morning.

Intending to reduce pollution levels in the capital city, the Delhi government collaborated with IIT-Kanpur to conduct cloud seeding trials.

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However, experts expressed concerns about the lack of long-term solutions to mitigate the rising pollution levels in Delhi, especially during winter months. They also warned about the impact of cloud seeding on soil and water bodies, as chemicals such as sulphur and iodide were injected into clouds.

Cloud seeding trials

The trial, aimed at inducing artificial rain, was part of the Delhi government's broader strategy to mitigate deteriorating air quality. According to Environment Minister Manjinder Singh Sirsa, the Delhi government conducted the trials in parts of Delhi, including Burari, Karol Bagh, Mayur Vihar, and Badli. More such exercises are planned over the next few days.

During the first trial, Cessna aircraft took off from Kanpur and released six flares at an altitude of nearly 4,000 feet above ground level, with a burn duration of 18 and a half minutes. The seeding points covered were Khekra, Burari, North Karol Bagh, Mayur Vihar, Sadakpur and Bhojpur.

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A second flight took off at 3.55 pm, deploying eight flares at a higher altitude of around 5,000-6,000 feet, with the first seeding point at Khekra at 4.08 pm, followed by Burari, around Mayur Vihar, Pavi Sadakpur, Noida, Bhojpur, Modinagar and Meerut, landing back at 4.45 pm.

Silver iodide and sodium chloride compounds were released from the aircraft to induce artificial rain.

According to Sirsa, each flare lasted for two to two-and-a-half minutes. He added that, "the clouds had a humidity of 15 to 20 per cent. Flares were released for 17 to 18 minutes".

No rainfall recorded

Soon after the first trial, Sirsa said IIT-Kanpur 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," he added. IMD data too showed no rainfall in Delhi till late evening.

Since the IMD informed that the wind direction was towards the north, areas falling under that region are being targeted.

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

According to news agency PTI, the IIT-Kanpur successfully executed the operation in a corridor measuring roughly 25 nautical miles in length and four nautical miles in width, with the largest distance covered between Khekra and a little north of Burari.

The team from IIT-Kanpur has expressed hope for good results from these systematically conducted experiments, Sirsa 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.

Reduced pollution levels

On the evening of October 28, the government, in a report, said that the cloud seeding trials reduced Particulate Matter (PM) at locations where the exercise was carried out, even as conditions were not ideal for it. The report also noted two precipitation events, Noida at 4 pm (0.1 mm of rain) and Greater Noida at 4 pm (0.2 mm).

Also Read: Delhi conducts first cloud seeding test to tackle air pollution

"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 was not an ideal condition for cloud seeding.

The official government report said data from 20 locations were collected for AQI monitoring, especially particulate matter PM2.5 and PM10, which will be directly impacted by cloud seeding. It also noted that winds were negligible at that time, but the denser moisture content created due to seeding particles helped in settling down a portion of these particles, which translated to these reductions.

A short-term measure

However, the experts are concerned about the lack of long-term solutions to the rising pollution in the city and said that the trials that were conducted so far were focusing only on urban areas. On the political front as well, the BJP government faced backlashes. 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.

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.

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As the Delhi government conducted the exercise on October 28, 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.

Early attempts at seed clouding

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.

According to climate scientist Roxy Mathew Koll from the Indian Institute of Tropical Meteorology (IITM), the first cloud seeding trial in Delhi was conducted during the monsoon of 1957, while the second attempt was made during the winter of the early 1970s.

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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.

Improved Delhi air quality

Following the trials, Delhi's air quality improved slightly on Wednesday morning but remained in the "poor" category with an overall Air Quality Index (AQI) of 273, according to the Central Pollution Control Board (CPCB).

On October 28, the city recorded an AQI of 294 at 4 pm, a marginal drop from Monday's reading of 301, which fell under the "very poor" category.

Despite the overall improvement, 11 out of Delhi's 38 monitoring stations continued to record AQI in the "very poor" range with readings above 300, data from the CPCB's Sameer app showed.

According to the CPCB, an AQI between zero and 50 is considered "good", 51 to 100 "satisfactory", 101 to 200 "moderate", 201 to 300 "poor", 301 to 400 "very poor" and 401 to 500 "severe".

Meanwhile, the minimum temperature in the national capital settled at 18.2 degrees Celsius, 2.1 degrees above normal, IMD said.

The maximum temperature is likely to settle around 28 degrees Celsius, and the IMD forecast shallow fog in the city on Wednesday. Relative humidity was 89 per cent at 8.30 am.

(With agency inputs)