What is Intertropical Convergence Zone (ITCZ)?

The Intertropical Convergence Zone (ITCZ) is an area of low pressure that forms where the Northeast Trade Winds meet the Southeast Trade Winds near the earth's equator. As these winds converge, moist air is forced upward. This causes water vapor to condense, or be "squeezed" out, as the air cools and rises, resulting in a band of heavy precipitation around the globe. This band moves seasonally, always being drawn toward the area of most intense solar heating, or warmest surface temperatures. It moves toward the Southern Hemisphere from September through February and reverses direction in preparation for Northern Hemisphere Summer that occurs in the middle of the calendar year. However, the ITCZ is less mobile over the oceanic longitudes, where it holds a stationary position just north of the equator. In these areas, the rain simply intensifies with increased solar heating and diminishes as the sun moves away. An exception to this rule occurs when there is an ENSO event, during which the ITCZ is deflected toward unusually warm sea surface temperatures in the tropical Pacific.

The formation of ITCZ:

The motion of the Hadley cell, which is driven by intense solar heating, induces the formation of the ITCZ, which provides precipitation for rainforests.