Delhi artificial rain on hold: What is the cloud seeding plan, how does it work?
Delhi environment minister Manjinder Singh Sirsa said that cloud-seeding is likely to be carried out within the next week.
Delhi environment minister Manjinder Singh Sirsa has said that the Capital is waiting for the trial of the artificial rain experiment, given that there were no suitable clouds at present.
According to the India Meteorological Department, no window is expected for the experiment until October 25.
"The day we get suitable clouds, we will conduct the trial immediately, as all preparations — from permissions to flight arrangements — are already in place," Sirsa told PTI news agency.
Earlier reports had said that the trial could take place any day after Diwali. However, the post-Diwali AQI spike has led to the plan being put on hold.
What is the artificial rain plan?
The cloud seeding project of the Delhi government was initially scheduled earlier this year in July, but has been postponed multiple times due to various reasons.
The plan was delayed due to the monsoon, changing weather patterns, disturbances, and at present, due to lack of cloud cover. No exact date has been fixed for the experiment yet.
To carry out the trial, Cessna aircraft has been stationed at Meerut and all necessary equipment is in place, Sirsa said. The pilots are licensed and authorities are waiting for the green signal by the IMD to start operations as soon as clouds form, the minister said.
Four days of trial flights have been successfully conducted over northwest Delhi, the zone chosen for the pilot project.
“Previous governments only talked; we actually did the groundwork in 7 months: approvals, agreements, MOUs, consultations with scientists and arrangements with pilots and aircraft,” Sirsa said, adding that the cloud seeding operations would take place within the next week.
How will the cloud-seeding work?
As part of the cloud-seeding, substances such as silver iodide (AgI) will be dispersed into clouds to facilitate the formation of ice crystals and enhance their ability to produce rain. Silver iodide aids in the creation of ice nuclei in clouds, which are necessary for artificial rain to occur.
Cloud-seeing can be categorised into two types, according to ScienceDirect:
• 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 emphasis on rain is because it can improve air qualityby 50–80 AQI points, depending on the intensity and spread. Therefore, if AQI is “very poor”, it may improve to “poor”, and if it is already poor, it may become “moderate” after rainfall, according to experts.
The project will be operated in collaboration with Indian Institute of Technology (IIT) Kanpur, which has modified a Cessna-206H aircraft for the project.
The Nimbostratus clouds, typically located between 500m and 6,000m above ground, have been identified as ideal for the seeding. However, these must contain at least 50 per cent moisture already.
The skies in Delhi at present lack sufficient moisture or cloud density, which is leading to delays for the trial.
