The zone of separation between the wind circulations proper to the northern and southern hemispheres. Over the Atlantic and Pacific Oceans, where it is closely related to the Doldrums, it is the boundary between the north-east and south-east trade-winds.
The equatorial convergence zone in the atmosphere.
(usually abbr. ITCZ): a zone (often rather broad, but sometimes quite narrow), which separates the 'air-masses' brought together by the low-level outflow from the sub-tropical high pressure belts north & south of the equator. Over the oceans, the zone can be well marked; over land, sensible heating usually leads to 'breaks' or other anomalies, and the regional-scale monsoon circulations also distort, or swamp the idealised structure of the ITCZ. Cloudiness (& hence precipitation activity) can vary sharply over a period of 24hr. Day-to-day change of position is often small, but the zone migrates north & south through the course of a year, roughly in sympathy with the changing position of the sun.