Intertropical convergence zone

Solar beating of tropical oceans warms the surface water, promoting evaporation. Where the equatorial surface waters are warmest and the northeast and southeast trade winds meet, a band of cirrostratus and cirrus clouds spreads out from convective precipitation regions. This area is known as the Intertropical Convergence Zone. 

INDOEX IPCC ITCZ Indian Ocean Experiment Intergovernmental Panel on Climate Change Intertropical Convergence Zone... 

Northern Hemisphere summer insolation during the early to mid-Holocene (Berger, 1978) resulted in increased heating over the Northern Hemisphere continents and thus intensified the thermal contrast between the land and the ocean. The increased heating over the continents resulted in the northward displacement of the intertropical convergence zone (ITCZ) and hence of the monsoon front, while the enhanced land-sea contrast increased the flux of moisture from the ocean to the continent. 

A study in the tropical Atlantic by Williams et al. involved measuring acetone, methanol, acetonitrile and dimethyl sulfide within the atmospheric marine boundary layer and the upper ocean [116]. Measurements were taken on either side of the intertropical convergence zone. This zone, which sailors commonly refer to as the doldrums, is an area around the equator where the southeast and northeast trade winds meet. Consequently, it is a natural barrier to atmospheric mixing between the hemispheres. This results in hemispheric gradients for VOCs whose atmospheric lifetimes are shorter than interhemispheric mixing times... 

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