<P> The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge . </P> <P> The ITCZ was originally identified from the 1920s to the 1940s as the "Intertropical Front" ("ITF"), but after the recognition in the 1940s and 1950s of the significance of wind field convergence in tropical weather production, the term ITCZ was then applied . When it lies near the Equator, it is called the near - equatorial trough . Where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage more common in Australia and parts of Asia . In the seamen's speech, the zone is referred to as the doldrums because of its erratic weather patterns with stagnant calms and violent thunderstorms . </P>

The wind system in the equatorial areas is known as