Asymmetry of the Intertropical Convergence Zone 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. The ITCZ would be expected to overlie the geographic equator according to symmetric solar radiation. However, the ITCZ is mostly perennial in the northern hemisphere and in the eastern Pacific and Atlantic Oceans. It was originally explained by the asymmetrical distribution of continents. However, the distribution of land and ocean is severely asymmetric in the Indian Ocean, yet the ITCZ moves back and forth there between the southern and northern hemispheres. Continents surround
Tropical instability waves El Niño conditions are present. Tropical instability waves are not related to tropical waves, which are atmospheric disturbances that propagate westward along the Intertropical Convergence Zone, sometimes giving rise to tropical storms. In both the Atlantic and Pacific oceans, a tongue of cold surface water usually extends westward along the equator from the continental margins. These "cold tongues" consist of water upwelling from the ocean depths, and are surrounded by warmer surface water in both hemispheres. The temperature difference between the cold tongues and the surrounding warm water is largest during the southern hemisphere winter. The Pacific cold tongue is