Asymmetry of the Intertropical Convergence Zone it is the equatorial upwelling that prevents the ITCZ being created at the equator. To explain this simply, upwelling brings cold water to the surface, which will cool the above atmosphere and make it stable because of relative high air density due to low temperature. Thus, this area of the equator is different compared to the strong vertical convection and abundant precipitation of the ITCZ. As a result, the SST is latitudinally asymmetric. Asymmetry of the Intertropical Convergence Zone There are a number of explanations of the asymmetry of the Intertropical Convergence Zone (ITCZ), known by sailors as The Doldrums.
Trade winds within the subtropical ridge. The weaker the trade winds become, the more rainfall can be expected in the neighboring landmasses. The term "trade winds" originally derives from the early fourteenth century late Middle English word "trade," meaning "path" or "track." The Portuguese recognized the importance of the trade winds (then the "Volta do mar", meaning in Portuguese "turn of the sea" but also "return from the sea") in navigation in both the north and south Atlantic ocean as early as the 15th century. From West Africa, the Portuguese had to sail away from continental Africa, that is, to west and