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,
Panthalassa two hemispherical belts were separated by the undulating Intertropical Convergence Zone (ITCZ). In northern Panthalassa there was mid-latitude westerlies north of 60°N with easterlies between 60°N and the Equator. Atmospheric circulation north of 30°N is associated with the North Panthalassa High which created Ekman convergence between 15°N and 50°N and Ekman divergence between 5°N and 10°N. A pattern which resulted in northward Sverdrup transport in divergence regions and southward in convergence regions. Western boundary currents resulted in an anti-cyclonic subtropical North Panthalassa gyre at mid-latitudes and a meridional anti-cyclonic circulation centred on 20°N. In tropical northern Panthalassa trade winds created