Why did cloud seeding not bring any rain in Delhi? What experts say

Manindra Agarwal, director of IIT Kanpur, says the possibility of triggering rain with such low atmospheric moisture was not very high

In an attempt to curb air pollution, the national capital Delhi saw its first cloud-seeding trial on Tuesday. The exercise, however, did not bring any showers, and the reason being attributed to this is low atmospheric moisture.

The trial was a part of the Delhi government's initiative to tackle the air pollution levels by inducing rain through artificial means.

Last week, a test flight was conducted over Burari, and small quantities of silver iodide and sodium chloride compounds were released from an aircraft to trigger artificial rain. But due to low atmospheric moisture, the test flight could not bring any rain.

Manindra Agarwal, the director of IIT Kanpur, said that the process of inducing artificial rain is an SOS solution to combat pollution levels. "When you have a crisis situation, very high pollution, it is one of the methods one can attempt to bring down pollution," he said in an interview with NDTV.

"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 further explained.

Clarifying that the mixture used by the team had only 20 per cent silver iodide and the rest was a combination of rock salt and common salt, he said 14 flares were fired on Tuesday.

Agarwal's institute is collaborating with the Delhi government on this project, and he said that although the first trial was unsuccessful, it had given a sense of hope for the team to continue.

"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 (Tuesday) 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," he said.

According to NDTV, in a report released on Tuesday, the government said the cloud-seeding experiments helped in bring about a reduction in particulate matter in places where the trials were conducted.

"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, PM10 level was 207, 206, 209, which got reduced to 177, 163, 177 at Mayur Vihar, Karol Bagh, and Burari, respectively," the report stated.

Delhi Environment Minister Manjinder Singh Sirsa, in an interview with India Today shared insights on the project. "Cloud is mandatory. Generally, we need moisture of over 50 per cent. IIT Kanpur carried out the experiment — we are dependent on them. This trial was done to check if we can do cloud seeding in moisture conditions of 10–15 per cent. Since IIT Kanpur was confident, we went ahead with it," he said.

The Minister said the initiative marks a “huge step taken by the government to mitigate pollution.” And if it is successful, it could initiate a long-term plan till February.