Why Didn't Cloud Seeding Cause Rain In Delhi? What IIT Kanpur Director Said

Attempts to induce rain through cloud seeding in parts of Delhi on Tuesday were "not completely successful" because the moisture content in the clouds was low and the process is not a magic bullet for the problem of pollution, but an SOS solution, IIT Kanpur Director Manindra Agarwal has said.

Speaking exclusively to NDTV on Tuesday, Agarwal, whose institute is collaborating with the Delhi government to carry out the experiment, also said attempts will be made again on Wednesday, and they are hoping for a better result. 

Explaining that the mixture used by the team has only 20% silver iodide and the rest is a combination of rock salt and common salt, Agarwal said 14 flares were fired on Tuesday. 

"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%. 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," the IIT Kanpur director said. 

"There have been conflicting reports of the predictions about rain today. Some say there will be rain, some say there won't be. But what our team found was that the cloud cover had very little moisture content. And this could be true about the part we flew over... So we do not expect any rain to occur today," he added. 

Agarwal said two more such flights will be conducted on Wednesday, and the process will continue when there is cloud cover.

Asked whether cloud seeding could be a long-term solution to the persistent problem of pollution in Delhi, the IIT director was clear that it is not.

"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.

The costs, he said, are high because the flights are being conducted from Uttar Pradesh, but those can be brought down substantially. 

"Any attempt which leads to a reduction of pollution benefits everyone. And even though it is not a permanent solution, even if it rains after a few days, at least it can provide some relief," he said. 

Government's Take

The Delhi government said in a report that the cloud seeding trials helped bring about a reduction in particulate matter in places where they were conducted. The report said two precipitation events were recorded - 0.1 mm of rain in Noida at 4 pm and double that in Greater Noida at the same time. 

"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.

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