Australia – December 30th, 2011

“Popcorn” clouds hang in a relatively uniform layer over the land by Brazil’s northeastern coast. These clouds form when water vapour is released into the atmosphere by photosynthesizing plants. Water vapour is more buoyant than dry air, so it rises and eventually condenses into clouds like the popcorn clouds shown here.

water vapour condenses, it releases heat into the atmosphere. The heat makes the air even more buoyant, and it rises. The higher it rises, the more the air expands and cools, which allows more water vapour to condense. Eventually, thunderstorms can form. The more concentrated clusters of clouds in the image are likely thunderstorms.