Inter-tropical Convergence Zone
Inter-tropical convergence zone (ITCZ) is a belt of converging trade winds and rising air that encircles the Earth near the Equator which is also called equatorial convergence zone. The rising air produces high cloudiness, frequent thunderstorms, and heavy rainfall; the doldrums, oceanic regions of calm surface air,
occur within the zone and extend for many hundreds of miles and is sometimes broken into smaller line segments.
The ITCZ follows the sun in that the position varies seasonally. It moves north in the northern summer and south in the northern winter.Over the Indian Ocean, it undergoes especially large seasonal shifts of 40°–45° of latitude. It is also is a key component of the global circulation system because solar heating in this region forces air to rise through convection which results in a plethora of precipitation.
The ITCZ (pronounced “itch”) is what is also responsible for the wet and dry seasons in the tropics. It exists because of the convergence of the trade winds. In the northern hemisphere the trade winds move in a southwesterly direction, while in the southern hemisphere they move northwesterly. The point at which the trade winds converge forces the air up into the atmosphere, forming the ITCZ.
The tendency for convective storms in the tropics is to be short in their duration, usually on a small scale but can produce intense rainfall. It is estimated that 40 percent of all tropical rainfall rates exceed one inch per hour. Greatest rainfall typically occurs when the midday Sun is overhead. On the equator this occurs twice a year in March and September, and consequently there are two wet and two dry seasons. In the Northern Hemisphere, the wet season occurs from May to July, in the Southern Hemisphere from November to February.