Cloud seeding delay explained: Why Delhi’s artificial rain is still on hold - the science and the wait behind clouds

Delhi AQI

Delhi Environment Minister Manjinder Singh Sirsa has said that the city is fully prepared to conduct its artificial rain experiment, but is waiting for the right weather conditions.

Currently, the skies over Delhi do not have the kind of clouds needed for the trial, and the India Meteorological Department (IMD) has indicated that no suitable window is expected before October 25.

“The day we get suitable clouds, we will carry out the trial immediately. All preparations, from permissions to aircraft arrangements, have already been completed,” Sirsa was quoted by PTI as saying.

The type of clouds suitable for seeding, called Nimbostratus clouds, need to be at altitudes between 500 and 6,000 meters and must contain at least 50% moisture. At the moment, Delhi’s skies are too dry and thin for the experiment.

According to the experts, even light rainfall can bring an improvement in Delhi’s air quality. Depending on how widespread and intense the rain is, the Air Quality Index (AQI) can drop by 50 to 80 points.

The Delhi government’s cloud seeding project was first planned in July this year, but it has faced several delays. The monsoon season, shifting weather patterns, and now the lack of proper cloud cover have all pushed back the trial.

A Cessna aircraft equipped with special cloud-seeding equipment is stationed at Meerut, ready to take off when the IMD gives its approval. Pilots are licensed and trained, and the project has already completed four successful trial flights over northwest Delhi.

“Previous governments only made announcements. We completed everything in seven months, from permissions, agreements, scientific consultations, to aircraft arrangements,” Sirsa said. The minister added that the operation will begin within a week once the IMD confirms cloud formation.

Cloud seeding is a scientific process that helps induce rainfall by releasing certain substances into clouds to encourage them to produce rain. In Delhi’s case, silver iodide (AgI) will be used. The particles help form ice crystals within clouds, which grow and eventually fall as raindrops.

Hygroscopic Cloud Seeding: This method accelerates the merging of droplets in liquid clouds, thus creating larger droplets which eventually lead to precipitation. In this, salt particles are generally released at the base of the cloud.

Glaciogenic Cloud Seeding: This method induces cloud formation in supercooled clouds by dispersing efficient ice nuclei like silver iodide or dry ice, which triggers ice nucleation and then precipitation.

The artificial rain project is being carried out in partnership with IIT Kanpur, which has modified the aircraft for this purpose.