Despite its name, much of the Amazon Rainforest is not actually rainy year round. Many areas experience a monsoon climate, with a season of heavy rains followed by a dry season that can last anywhere from one to seven months. North of the equator, the rainy season occurs from June-August. South of the equator, it runs from October or November through March, April, or May. The processes that initiate the switch in where the rain falls are something of a mystery. In 2007, scientists discovered evidence that the forest itself triggers the switch. Increasing leaf area throughout the dry season may set off a chain of events that leads to a reversal in the north-south winds that carry moisture into one hemisphere or another.
This trio of photo-like images illustrates steps in the initiation of the wet season in the southern Amazon in 2006.
