Why are doldrums also called the Intertropical Convergence Zone?

The Doldrums are the regions of air directly above the Equator that extends about 10 degrees North and South. This region is characterized by having very little lateral movement of air and a large amount of precipitation. This is due to the fact that, as the Equator heats up year round, the air above is constantly being heated, creating a rising effect. Hotter air is less dense than colder air and is lifted up while colder air rushes in to take its place.

The rising hot air will blossom outward away from the equator, moving North and South before plummeting back down around the 23 degree N and S latitudes. The falling air then reverses direction and sweeps back towards the equator. These winds are called the Trade Winds and were used by early sailors to propel their sailing ships towards the New World and Caribbean. 

The Trade Winds collide in the center of the tropics, where the air re-heats and rises, beginning the process all over again. This giant Convection Cell, or Hadley Cell, gives us the rising hot air of the Doldrums, the falling cold air of the Horse Latitudes (23 degrees North and South) and the Trade Winds. The area where the Trade Winds meet is known as the ITCZ: Intertropical Convergence Zone. The name references the convergence of the North and South Trade Winds in the center of the Tropics which lie over the Equator. Intense storms and precipitation are normal for this region due to all of the rising hot air building large and heavy clouds.