 "A pedestrian walks amid smog, near India Gate in New Delhi on October 29, a day after cloud seeding trials took place. Unfortunately, it didn't induce rain, leaving Delhiites dismayed. AFP")
On Tuesday (October 28), many Delhiites looked to the skies, hoping for the clouds to open up and drench India’s National Capital with rain — similar to scenes from Bollywood movies. After all, the Delhi government trialled a cloud-seeding experiment to induce artificial rain, in an effort to clean the air in the world’s most polluted city.
Alas, this experiment didn’t succeed, leaving the residents of Delhi with no rain and forced to choke on ‘poor’ and ‘very poor’ air.
Here’s what happened.
Delhi trials cloud seeding to battle air pollution
After years of flirting with the idea of cloud seeding to battle Delhi’s air woes — each winter, the national capital struggles with toxic haze and headlines reporting of how Delhi is a “gas chamber” — the Bharatiya Janata Party (BJP) government announced that it would go ahead and carry out this experiment to trigger artificial rain to wash away pollutants and improve Delhi’s Air Quality Index (AQI).
On May 7, the Delhi government approved a proposal to conduct five cloud seeding trials at a total cost of Rs 3.21 crore, meaning each run costs about Rs 64 lakh.
And on Tuesday, as per the MoU signed between the Delhi government and IIT-Kanpur, two such experiments were carried out to induce artificial rain.
In the first trial, which took place at 1.30 pm local time on Tuesday, a Cessna aircraft from IIT Kanpur sprinkled silver iodide mixture over clouds over Northwest Delhi’s Burari, Mayur Vihar and Karol Bagh. Later, between 3.30 pm and 4.15 pm, a similar exercise was carried out a second time over the same areas.
As per reports, the aircraft fired 16 flares — eight in each trial — containing silver iodide and sodium chloride compounds in attempts to induce rain.
Soon after the first trial, Delhi’s Environment Minister Manjinder Singh Sirsa said that said IIT-Kanpur had relayed that rain could happen within 15 minutes to four hours after the exercise.
But Delhi sees no rain
However, as minutes turned into hours, Delhi saw no rain with most parts of the capital recording air quality levels in the ‘very poor’ category.
But why is it that India’s capital witnessed no rain after the cloud seeding experiment?
Manindra Agrawal, director of IIT Kanpur, explained that the cloud seeding trial was “not completely successful” because the moisture content in the clouds was low. “There hasn’t been any rain so far. So, in that sense, it was not completely successful. But, unfortunately, the clouds that are present today do not have very high moisture content. I am told it was only up to 15-20 per cent. So, the possibility of causing rain with such low moisture content is not very high. But this trial has given more confidence to our team that we can continue conducting them,” said the IIT Kanpur director to NDTV.
Typically, for cloud seeding to be successful, humidity levels of over 50 per cent is needed for the seeding agents, such as silver iodide or salt-based compounds, to effectively stimulate condensation and precipitation.
Other experts also explained why cloud seeding didn’t induce artificial rain in Delhi. Shahzad Gani, Assistant Professor at the Centre for Atmospheric Sciences, IIT Delhi, told Economic Times that Delhi’s winter weather is usually too dry for effective cloud seeding. “In the winter season, the weather in Delhi is typically very dry, with very little moisture in the air. The only time it rains is when a western disturbance influences the plains.”
Scientist Thara Prabhakaran, who was involved in a similar experiment in Maharashtra’s Solapur, also noted that cloud seeding takes time to induce rain. “It is not easy to do cloud seeding because there’s inherent variability in each cloud. It depends on the weather, the moisture, the size of the clouds, the origin of the clouds. We did over 200 different flights and trials to come to basic understanding,” she was quoted as telling The Print. “If you’re investing in cloud seeding, you should be able to prove the rainfall is actually because of seeding, robustly with experiments. It can’t happen with one or two trials.”
Akshay Deoras, research scientist at the National Centre for Atmospheric Sciences, University of Reading, further explained that people should understand that just because there are clouds, cloud seeding will succeed.
“In winter, cloud seeding should ideally be done only when suitable rain-bearing clouds appear — typically during western disturbances,” he told IndiaToday.
Effectiveness of artificial rain
Experts have also noted that while cloud seeding could help with Delhi’s pollution woes , it’s not a panacea for the problem.
In fact, when the Delhi government announced their cloud seeding plan, two professors at Delhi’s Centre for Atmospheric Sciences condemned it as a “gimmick”. “It is a textbook case of science misapplied and ethics ignored,” said Shahzad Gani and Krishna AchutaRao, writing in The Hindu.
They compared it to “smog towers” that were erected in Delhi by the previous government, at the cost of billions of rupees, but were found to be largely ineffectual at improving air quality.
Even IIT-Kanpur’s director, Manindra Agrawal, noted that cloud seeding is only an SOS option and couldn’t be a long-term solution to Delhi’s air woes. “It is an SOS solution. When you have a crisis situation, very high pollution, it is one of the methods one can attempt in order to bring down pollution. It is not a permanent solution. The permanent solution, of course, is to control the sources of pollution. And, ideally, we should reach a point when there is no need for cloud seeding, because there isn’t any pollution. But until that happens, this is one tool which is available for reducing pollution to an extent,” he explained.
Delhi government sees a silver lining
But despite seeing no rain following the cloud seeding experiment, the Delhi government seemed buoyed by the results.
According to government officials, the AQI, PM2.5 and PM10 — the most direct pollution markers — saw a dip after the exercise. Data provided by them showed that PM2.5 at Mayur Vihar, Karol Bagh, and Burari was 221, 230, and 229 ug/m³, which fell to 207, 206, and 203 ug/m³ respectively after the operation. Similarly, PM10 at the same sites dropped from 207, 206, and 209 ug/m³ to 177, 163, and 177 ug/m³ post-seeding.
Delhi’s Environment Minister has noted that they will carry out more experiments in the coming days, depending on atmospheric conditions. He further added that nine to 10 more trials are planned, targeting areas in northern Delhi and its outskirts, guided by wind directions provided by the India Meteorological Department (IMD).
With inputs from agencies