Cloud seeding: India
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What is "cloud seeding"
K. Lakshmi, March 19, 2017: The Hindu
Cloud seeding is an artificial way of inducing moisture in the clouds to cause rainfall. Weather experts recall that the State government attempted cloud seeding initiative in 1975 after a poor Northeast monsoon in 1974. The Indian Institute of Tropical Meteorology, Pune, has done several experiments at the national level.
R.G. Subramanian, former radar meteorologist who was deputed to work with Chennai Metrowater between 1984-87 on cloud seeding, recalled how the experiment was carried over catchment areas of the city reservoirs then.
Type of clouds
“Only certain kind of clouds can be seeded and it needs to have enough nuclei to process cloud seeding and thunder cloud development. We took the help of a U.S. firm, Atmospheric Inc, California, who guided us with their pilots and aircraft. We used silver iodide particles in the form of candles and fitted them on to the wings of aircraft. These candles were burnt and released into cloud masses at an altitude above 20,000 feet,” he said.
Not unfailing
However, this cannot be done in dry weather conditions. “We can experiment cloud seeding only when the cloud is in a developing stage. We cannot quantify the volume of rainfall that the experiment will bring. Even then, we could not prove that the cloud seeding caused rains as these clouds could otherwise too had the possibility of developing on their own,” he said.
Mr. Subramanian recalled that there was a heavy downpour that lasted for over 10 days in November 1985. But, there was no means to relate to cloud seeding experiment then.
In May 2003, cloud seeding was attempted through aerial spraying of common salt instead of silver iodide. But, it failed as there were no rain-bearing clouds.
Attempts, state-wise
2017: Maharashtra
Jacob Koshy, Clouds over Maharashtra will have a silver iodide lining, February 11, 2017: The Hindu
Seeding involves spraying chemicals into clouds.
State government responds to frequent droughts in Vidarbha with a three-year cloud seeding experiment
During monsoon 2017, weather scientists will fly airplanes loaded with silver iodide over clouds hovering above Solapur, Maharashtra and begin a three-year investigation into an old question: does cloud seeding produce sufficient rain?
The ₹250-crore programme, coordinated by the Indian Institute of Tropical Meteorology, will be the first controlled experiment to quantify the extent to which clouds form water drops large enough to make rain.
Seeding involves spraying chemicals into clouds. China used the technique during the 2008 Olympics to veer rain away from the inaugural venue and now has a full-fledged department that blasts rockets into clouds to induce rain and control pollution. “The benefits of cloud seeding aren’t well understood. Lots of organisations make claims,” Madhavan Rajeevan, Secretary, Ministry of Earth Sciences, said. “It’s time we have a proper scientific evaluation that State governments can rely upon.”
Maharashtra has frequently toyed with the idea of cloud seeding because of the frequency of droughts over the Vidarbha region. The State Cabinet had approved a plan to seed clouds for 113 hours with a rainfall level of 1,381mm, at ₹28 crore. However above-normal rains pushed the plan to the back-burner.
For their experiment, scientists will fly two aircraft and spray dry ice and silver iodide on 100 clouds and compare them with 100 unseeded clouds. Ground radar will track the clouds and verify which ones contributed rain. The programme will account for the variability of the monsoon. The move is part of a larger experiment of the Earth Sciences Ministry to understand how clouds and aerosols interact and influence climate.
2017, Varshadhare : Karnataka
Faced with the prospect of a fourth consecutive drought year, Karnataka has finally begun a project to harness rain-bearing clouds over the next two months. In the ongoing monsoon period, Karnataka is facing a cumulative rainfall deficiency of around 25 per cent till date, while the deficit across the country as a whole is four per cent.
‘Varshadhare’, a cloud-seeding project, was flagged off by Karnataka's Panchayat Raj Minister HK Patil and Agriculture Minister Krishna Byregowda at the Jakkur aerodrome in Bengaluru.
Cloud-seeding is a kind of weather modification procedure that attempts to enhance the amount of precipitation from the clouds to generate more rain. Karnataka is resorting to cloud-seeding after 14 years. Previously, the State had carried out such an operation in 2003.
Hoysala Projects Pvt Ltd, the designated agency to carry out the cloud-seeding, will take up the operations from the airports of Hubli and Bengaluru over the next 60 days.
Three Doppler radars are being set up at Bengaluru, Gadag and Surpur (Yadgir district) to detect the rain-bearing clouds and enable their seeding. As part of the seeding strategy, special aircraft will disperse the chemical silver iodide as they fly through rain-bearing clouds that will trigger and enhance the precipitation. “We expect to enhance the rainfall precipitation by around 15-20 per cent," said Srinivas, Project Manager at Hoysala Projects.
Rain deficiency has hurt the pace of the ongoing kharif sowing operations while impacting the inflows in reservoirs and tanks. Several towns in North and Central Karnataka continue to face drinking water scarcity. According to the IMD, cumulative rainfall deficit in South Interior Karnataka is pegged at 26 per cent, while in North Interior Karnataka the deficiency is 19 per cent. Coastal Karnataka faces a rain deficit of 23 per cent.
According to G Srinivas Reddy, Director, Karnataka State Natural Disaster Monitoring Centre, though the rainfall had picked up in August, cumulative deficiency exists in 17 of the 30 districts. About 90 of the 176 taluks still face deficit rains, while three had scanty precipitation. Only 12 taluks had excess rains, while 71 had normal rainfall so far.
Besides Karnataka, Kerala also faces a 26 per cent deficiency in rainfall so far. Eight meteorological subdivisions accounting for 21 per cent of the geographical area of the country are facing cumulative deficiency this monsoon season, including West and East Madhya Pradesh, Western UP, Haryana, Chandigarh and Delhi.
