Intertropical Convergence Zone Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge. The ITCZ was originally identified from the 1920s to the 1940s as the "Intertropical Front" ("ITF"), but after the recognition in the 1940s and the 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,
Winds in the Age of Sail them where they wanted to go. During the age of sail winds and currents determined trade routes and therefore influenced European imperialism and modern political geography. For an outline to the main wind systems see Global wind patterns. Pilotage or cabotage, in one sense, is the art of sailing along the coast using known landmarks. Navigation, in one sense, is the art of sailing long distances out of sight of land. Although the Polynesians were able to sail the Pacific (with great difficulty) and people regularly sailed north and south across the Mediterranean, before the time of Columbus nearly all