- 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.
- The move is part of a larger experiment of the Earth Sciences Ministry to understand how clouds and aerosols interact and influence climate.
What is cloud seeding? |
| Cloud seeding is the process of spreading either dry ice, or more commonly, silver iodide aerosols, into the upper part of clouds to try to stimulate the precipitation process and form rain.
Since most rainfall starts through the growth of ice crystals from super-cooled cloud droplets (droplets colder than the freezing point, 32 deg. F or 0 deg. C) in the upper parts of clouds, the silver iodide particles are meant to encourage the growth of new ice particles. The history of cloud seeding has experienced uncertain results because it can never be known whether a cloud that rains after seeding might have rained anyway. This is because seeding is performed on clouds that look like they have some potential for producing rain. |
- Silver iodide is an inorganic compound with the formula AgI.
- The compound is a bright yellow solid, but samples almost always contain impurities of metallic silver that give a gray coloration.
- The silver contamination arises because AgI is highly photosensitive.
- This property is exploited in silver-based photography.
- Silver iodide is also used as an antiseptic and in cloud seeding.