China’s state-run Aerospace Science and Technology Corporation has announced their plan to build a massive network of cloud-seeding devices – the largest in the world – on the mountain ridges lining central Asia’s Tibetan Plateau with the hope of increasing rainfall in the region.
If the system operates according to plan, additional rainwater totaling up to 10 billion cubic meters (353 billion cubic feet) could fall over the Plateau – a 2,500,000-square-kilometer (970,000-square-mile), high-elevation arid steppe that stores and distributes freshwater from glacier melt, mountain springs, and 10 of Asia’s major rivers. More than 1.35 billion people rely on water from this massive source, yet increased demand due to population growth and a barrage of water-greedy industrial projects in the area, combined with accelerated melting of Himalayan ice caused by climate change, threaten to compromise the supply in future.
Cloud seeding is a proven method for promoting rainfall by introducing microscopic particles, most commonly silver iodide, into the air so that water molecules present in the atmosphere have a substrate to form ice crystals on. Natural rain forms the same way: If enough water vapor globs onto natural particulates, the subsequent crystals will eventually become so heavy that they fall to the ground, melting as they go.
According to a report from the South China Morning Post, cloud-seeding initiatives began testing in the region over 10 years ago. However, early versions of the rocket-like burning chambers used to launch the silver iodide particles into the air could not stay lit in the low-oxygen environment at 5,000 meters (16,400 feet).
After finally creating a design that could withstand the harsh conditions with little to no maintenance, the aerospace agency teamed up with Tsinghua University to build and operate tens of thousands of chambers positioned on southern-facing ledges of Tibetan mountains.
The network of cloud seeders – called Tianhe, or “Sky River” – will be turned on remotely when weather satellites indicate that incoming air is suitably damp.
Though the land acts as a massive reservoir, most of the Plateau receives very little natural rainfall. The Himalayas flanking the area’s southern rim lie in the path of warm, moist air blowing northwards from the Bay of Bengal. As this air is forced upwards by the range’s foothills, the vapor condenses and falls as massive monsoons across regions in the Plateau’s southeast corner. By the time the air has moved northwest over the Plateau’s main expanse, too much of the air’s vapor has been lost for significant rain to form, and most of what remains falls as snow.
By placing the chambers in the path of the northbound air, the silver iodide seeds will theoretically allow the minimal moisture to precipitate over the dry Plateau.
“[So far,] more than 500 burners have been deployed on alpine slopes in Tibet, Xinjiang and other areas for experimental use. The data we have collected show very promising results,” an unnamed researcher told the South China Morning Post.
“Sometimes snow would start falling almost immediately after we ignited the chamber. It was like standing on the stage of a magic show."