Hidden Structures in Clouds May Solve a Longstanding Mystery About Rainfall

It's well known that where there's smoke there's fire, but did you know that where there's rain there's ice? Or so the conventional thinking goes, as atmospheric ice crystals allow raindrops to grow large and heavy enough to fall from cold clouds. There are also 'warm clouds', which generate much of Earth's rain, especially in the tropics, and influence our global energy balance.  Yet how raindrops form inside these sky-borne marshmallows made of water is one of the biggest puzzles in atmospheric science – and a barrier to precise climate forecasts.  Fortunately, scientists have just taken a significant step toward solving this mystery, revealing the previously invisible structures that breed raindrops in warm clouds.