Why didn’t Delhi get rain after cloud seeding? Scientists explain what went wrong and what’s next

The much-awaited cloud seeding experiment in Delhi on Tuesday did not bring the expected rainfall, as the clouds lacked enough moisture. However, scientists from IIT Kanpur, who are working with the Delhi government on the project said that the trial boosted their confidence for future attempts despite limited success.

Why didn’t it rain in Delhi?

IIT Kanpur Director Manindra Agarwal said that the first round of cloud seeding on Tuesday did not produce rain because the moisture in the clouds was only about 15-20%, far below the ideal level.

“There hasn’t been any rain so far, so in that sense, it was not completely successful,” he was quoted by NDTV as saying. The team used 14 flares containing a mixture of 20% silver iodide, with the rest made up of rock salt and common salt, to encourage condensation and rainfall.

Agarwal explained that the aircraft flew over areas where clouds were present, but the low humidity made rainfall nearly impossible. Despite this, he said the experiment was valuable because it demonstrated that the team could carry out such operations effectively and safely.

"There have been conflicting reports of the predictions about rain on Tuesday. Some said there will be rain, some said 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 did not expect any rain to occur on Tuesday," he added.

More cloud seeding trials planned in Delhi

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

The researchers plan to keep testing whenever there is enough cloud cover in the sky. “Some forecasts had predicted rain, while others didn’t. Our findings show the clouds we flew through had very little moisture, which explains the lack of rain,” he said.

The IIT director also said that the project is still experimental. The main aim is to study the technique’s effectiveness in Indian climatic conditions, particularly for addressing Delhi’s severe winter pollution.

Can cloud seeding be a long-term solution?

When asked if cloud seeding could be a long-term solution to Delhi’s air pollution, Agarwal said, “It is an SOS solution, something we try during an emergency. When pollution levels are dangerously high, cloud seeding can help reduce it temporarily by bringing down dust and particulate matter through rain. But the real solution lies in controlling pollution at its source.”

"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 reports small gains

According to a report from the Delhi government, the cloud seeding attempt did show slight improvement in air quality, even without significant rainfall. Small amounts of precipitation, 0.1 mm in Noida and 0.2 mm in Greater Noida, were recorded after the operation.

The report also mentioned a reduction in pollution levels at several monitoring points. "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.