Monday, May 7, 2007

Cloud Seeding

Cloud seeding is proposed by John Latham and Stephen Salter, who suggest to spray droplets of seawater high up into the air, so that the tiny particles of salt from these droplets will make clouds thicker and more reflective. The project featured prominently in the BBC documentary:
Five Ways To Save The World

Stephen Salter proposes to make rain with floating wind turbines that make very choppy waves, known as Faraday waves. A high-frequency ultrasonic generator would spin seawater around inside a grooved drum, producing tiny waves that are thinner than a human hair, throwing tiny droplets of water from their crests up into the air. As this fine mist of sea-spray evaporates, tiny particles of sea-salt remain in the air and get sucked up into the air, especially when the sunshine causes rising currents of air. These little salt particles act as centres attracting extra droplets to form darker clouds further up in marine stratocumulus clouds. Stephen envisages a multitude of ships to criss-cross the oceans, remotely controlled with their position tracked through GPS and their destination determined by wheather patterns. This idea of making rain in this way could also be combined with another idea discussed earlier in this group, i.e. of exploiting temperature differences in the sea.

The deeper you go down into the ocean, the colder it gets. At the lowest points, the temperature is near freezing point. Ships could drag a pipe along, reaching down a few hundred metres into the ocean. Through this pipe, cold water could be pumped up by a solar-powered pump to be released back into the sea from a little tower of, say, two metres high. As the cold water falls down into the sea, the evaporation will act as an air-conditioner. Furthermore, condensation around the top of the pipe will drip down and can be captured in containers, to be sold as fresh water. So, apart from harvesting clean, potable water in the above way, such a ship could also be anchored at a location where it could throw part of the seawater up into the air in the way Stephen Salter proposed, as a fine mist, in order to produce more rain in the proximity of a dry area on land.
Sam Carana - Tabling ideas - From Rainmaking to Sunshields - March 3 2006

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