Cloud seeding experiment over Solapur led to 18% rise in rainfall, finds study

New Delhi: A cloud seeding experiment to artificially trigger rain over the Solapur region of southwest Maharashtra led to 18 per cent more rainfall than in normal conditions, a study has revealed.

In the results of the study published in the Bulletin of the American Meteorological Society (BAMS), scientists from the Pune-based Indian Institute of Tropical Meteorology and other institutes found that hygroscopic cloud seeding enhanced rainfall in a rain shadow area spanning 100 square kilometres in Solapur.

Hygroscopic seeding is done in warm convective clouds with a cloud base height greater than zero degree Celsius. It uses hygroscopic flares of calcium chloride particles released at the convective cloud base.

"As per radar observations over an area spanning 100 sq km downwind of the seed location, there was a relative enhancement of rainfall by 18 per cent in the 'seed' category clouds," Thara Prabhakaran, the project director of Cloud Aerosol Interaction and Precipitation Enhancement Experiment told PTI.

Prabhakaran is one of the authors of the study published in BAMS, a peer-reviewed journal, earlier this week.

The cloud seeding experiment was carried out between 2017-19 with scientists evaluating 276 clouds to test the effectiveness of the procedure that was conducted using a specially fitted aircraft as part of a project of the Ministry of Earth Sciences.

All measurements were done using a wide network of state-of-the-art equipment such as automatic rain gauges, radars, radiometers, and aircraft.

The scientists also conducted the glaciogenic seeding method in cold clouds having both ice and water. The process uses ice-nucleating silver iodide particles inside clouds to enhance ice particle production and increase rain from the cold part of the cloud.

Scientists found that the glaciogenic seeding did not cause significantly different rainfall between seeded and non-seeded clouds at the seeding location. However, a relative increase in rainfall was seen downwind of the seeded area, supported by the synoptic weather conditions.

The scientists have recommended using hygroscopic cloud seeding to enhance rainfall in rain-deficient and water-stressed areas in Indian settings under suitable conditions, backed by statistical, physical, and numerical evidence.