Why is cloud seeding used

Cloud Seeding Program. What is Cloud Seeding? How we Cloud Seed Cloud seeding can be done from ground-based generators or aircraft. Benefits of Cloud Seeding Cloud seeding is used all over the world as a method for enhancing winter snowfall and increasing mountain snowpack, supplementing the natural water supply available to communities of the surrounding area. DRI's Updated Privacy and Cookies Policy We use cookies to offer you a better experience on our website, analyze our site traffic, and to provide social sharing functionality for our online stories.

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Scientists have pointed to the climate crisis as a key cause. This article is more than 7 months old. An empty irrigation canal at a tree farm in Corrales, New Mexico. Climate crisis: recent European droughts 'worst in 2, years'. But in the mountains, where the economy relies on snowfall, these same methods can be used to get an edge over rival resorts.

Cloud seeding is most commonly done out of airplanes. Planes fly into selected cloud formations and release packets of microscopic silver iodide particles using flares. When the particles meet cool moisture in the clouds, they trigger the formation of ice crystals and raindrops. Most research has estimated that, on average, you can get a precipitation increase of around 10 percent; with some storms, you can get 25 percent, and in other storms, you get zero.

But not every cloud can be seeded, and the process is as much art as science. Earlier studies would inject silver iodide into clouds, then compare precipitation gauges in areas inside and outside the seeding zone. The challenge with measuring the effect of weather modification is that natural rain- and snowfall variability is 10 to times as large as the amount of precipitation augmented by seeding, Bruintjes says.

They conducted more than tests, randomly selecting clouds to seed and clouds to be their unseeded controls. The scientists also took advantage of new developments in remote-sensing and atmospheric modeling to examine dynamics inside a small subset of seeded clouds. Using cloud radar, a laser-based version of radar known as lidar, and other techniques, the team examined the chain of events, beginning with the distribution of the seeding material then moving to the conversion of supercooled liquid water into ice and finally to the deposition of snowfall.

With the reflectance signal from lidar in particular, the researchers were able to monitor the real-time decline of supercooled liquid water as it condensed on the silver iodide particles. Cloud radar tracked the increase in the number of snow particles.

Remote-sensing observations are valuable because radar can describe growth of snow in a cloud in a much more immediate way than snow gauges can, says Bart Geerts , an atmospheric scientist at the University of Wyoming who was part of WWMPP. The remote-sensing equipment combined with modeling confirmed an increase in the size and number of snow particles within the cloud after seeding. In the end, though, the researchers did not have enough remote-sensing data over a sufficiently long period of time to quantify the impacts they thought they saw.

The temperature and the wind speed and direction have to be just right. The NAS report concluded that it is difficult to show clearly that cloud seeding has a very large effect. Even if cloud seeding does succeed at increasing precipitation, environmental activists are concerned about its impact.

Natural background levels of silver iodide in snow are about 1 to 2 parts per trillion, and after seeding, researchers look for levels from 4 to 20 ppt. Although silver is toxic to aquatic organisms in large doses, the levels found in surface water after seeding are well below the toxic threshold of 50, ppt, Benner says.

Aside from the toxicity of silver, some cloud-seeding critics raise concerns about messing with the balance that Mother Nature holds on the atmosphere. The amount of moisture in the atmosphere is determined by the balance between evaporation and precipitation. If cloud seeding is done on a large scale, it might lead to increased evaporation from locations outside the seeding area, Jackson says.

As chronic drought settles into parts of the Great Plains and western U. With countries increasingly spending hundreds of millions of dollars on weather modification, he argues, more research is needed to understand if the practice works and what its environmental, social, and governance impacts will be. This article has been translated into Chinese and can be found here.

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