Have We Finally Found the Recipe for Making Rain?

An electric shock might be just the thing to persuade a cloud to produce some rain. New research suggests that supercharging a cloud could increase the attractive forces between droplets and help raindrops to grow. Have we finally found the recipe for making rain? From a report: Electric charge is all around us. Thunderclouds literally crackle with it, but even the air we breathe has some charged aerosols and droplets in it. Giles Harrison, a meteorologist at the University of Reading, and colleagues have been investigating the electric charge of drops in non-thunderstorm clouds. In calculations led by Maarten Ambaum and published in Proceedings of the Royal Society A, they show that the greater the variation in charges, the stronger the attraction between droplets. "This advances our understanding of how charge influences drop growth and brings a new aspect to answering the age-old question: why does it rain?" says Harrison. Last year Harrison and his colleagues, who have been funded by the United Arab Emirates to research rain enhancement, flew drones equipped with ionisers into clouds and experimented with releasing positive and negative charges into the air. The new results will help them fine-tune these experiments, potentially to find ways to hasten the formation of rain where it is needed.

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