The Engine Room

The tropics sit between the Tropic of Cancer and the Tropic of Capricorn, where the sun strikes most directly. This band soaks up more solar energy than anywhere else on Earth.

That heat boils off huge amounts of ocean water. The rising vapor powers storms, rainfall, and wind patterns that ripple out to every other region on the planet.

Near the equator, trade winds from the north and south crash together in the Intertropical Convergence Zone. There is nowhere for that air to go but up.

As it rises it cools, and the moisture pours out as rain. This is why the world's biggest rainforests sit in a belt around the middle of the globe. The zone slides north and south with the seasons, setting the rhythm of wet and dry months.