Submission + - Some raindrops exceed their terminal velocity (sciencemag.org)
sciencehabit writes: New research reveals that some raindrops are “super-terminal” (they travel more than 30% faster than their terminal velocity, at which air resistance prevents further acceleration due to gravity). The drops are the result of natural processes—and they make up a substantial fraction of rainfall. Whereas all drops the team studied that were 0.8 millimeters and larger fell at expected speeds, between 30% and 60% of those measuring 0.3 mm dropped at super-terminal speeds. It’s not yet clear why these drops are falling faster than expected, the researchers say. But according to one notion, the speedy drops are fragments of larger drops that have broken apart in midair but have yet to slow down. If that is indeed the case, the researchers note, then raindrop disintegration happens normally in the atmosphere and more often than previously presumed—possibly when drops collide midair or become unstable as they fall through the atmosphere. Further study could improve estimates of the total amount of rainfall a storm will produce or the amount of erosion that it can generate.
