IIT-Kanpur tried cloud seeding despite ‘no clouds’ alert

IIT-Kanpur tried cloud seeding despite ‘no clouds’ alert

Despite inputs from the India Meteorological Department (IMD) that clouds on October 28 in Delhi would be insufficient to coax artificial rain, researchers from the Indian Institute of Technology Kanpur went ahead with their plan of flying their Cessna plane and firing 10 kg of a concoction of silver iodide, common salt and rock salt into the clouds to tear them. Twice. And failed both times.

That Tuesday — with Delhi’s air quality predictably ‘poor’ — it was the first time the capital had experimented with cloud-seeding since 1972 and for the first time ever, with the express plan of improving air quality.

Cloud seeding, or spraying fine chemical aerosols into rain clouds to induce rain, has been a subject of investigation in India for decades with the acknowledged authorities on the subject — the IITM, Pune — having conducted careful experiments on the effectiveness of cloud seeding to enhance monsoon rain since 2009.

“We shared information with them (IIT-Kanpur) on the cloud situation but didn’t give any specific input on whether they should go ahead with cloud seeding,” a senior scientist with the Ministry of Earth Science (MoES) told The Hindu. “We didn’t give any advice because the Indian Institute of Tropical Meteorology (IITM), Pune, has conducted several cloud seeding experiments over the years and there is still no concrete evidence that this works reliably. We didn’t give any recommendation but shared our input regarding clouds, which was that there were no clouds.”

M. Mohapatra, Director-General, IMD, confirmed to The Hindu that cloud inputs were “shared”, but he added that it was generic information.

Manindra Agrawal, Director, IIT-Kanpur, and the public-facing official of the institute’s programme, said that while his team had interacted with “IITM and IMD” previously, their feedback had been “negative” and that “it (cloud-seeding for winter pollution) wouldn’t work.”

“But it does work,” Mr. Agrawal told The Hindu. “It may not have worked in India but it has in China and the United Arab Emirates. The decision to go ahead with the trial despite the IMD’s forecast for unfavourable clouds was deliberate,” said Mr. Agrawal, because the team wanted to test the efficacy of their “proprietary solution,” which was “20% silver iodide, rock salt and common salt,” with the flares manufactured at Sivakasi, Tamil Nadu. “We were aware that there was less than 15% moisture (in the clouds), which is too little for seeding. However, we needed data to find out the potency of our indigenously made salt mixture.”

The implicit rule of cloud seeding is that it can only help in adding more water to clouds with minimum quantities of water vapour, called ‘warm clouds.’

But if clouds already have water vapour, they would rain anyway. So what’s the gain from seeding?

The IITM-CAIPEX (Cloud Aerosol Interaction and Precipitation Enhancement Experiment) was designed to answer just that. Just as medical researchers test new drugs in randomised clinical trials, by having a group of participants receive a drug and another, only believing they have ingested a drug and then evaluating if the actual recipients had improved health outcomes, the CAIPEX researchers flared tubes of chemical powder attached to planes’ wings to the base of selected warm clouds over Solapur, Maharashtra — a rain-and-water deficit region. They chose precisely 276 warm clouds — and flared 151, with the rest — 125 — left unseeded.

The researchers were able to send aircraft — each sortie cost ₹15 lakh — to the intended clouds to be seeded. It turned out that half the seeded and nearly 70% of unseeded clouds ‘dissipated’ without giving any rain. About 40% of the seeded clouds gave rainfall and 27% unseeded clouds gave rainfall.

Overall, seeded clouds gave an average 46% more rain at the seeded locations relative to the unseeded ones. Over a 100 sq.km. area downwind, there was 18% more rain in the seeded clouds versus the unseeded. Warm-cloud seeding was appropriate for enhancing only monsoon rainfall.