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Encyclopedia > Intertropical convergence zone
The thunderstorms of the Intertropical Convergence Zone form a line across the eastern Pacific Ocean.
The thunderstorms of the Intertropical Convergence Zone form a line across the eastern Pacific Ocean.

The Intertropical Convergence Zone (ITCZ), also known as the Intertropical Front, Monsoon trough, Doldrums or the Equatorial Convergence Zone, is a belt of low pressure girdling Earth at the equator. It is formed by the vertical ascent of warm, moist air from the latitudes above and below the equator. This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... The Glossary of Meteorology defines a monsoon trough simply: A line in a weather map showing the locations of minimum sea level pressure in a monsoon region. ... A large low-pressure system swirls off the southwestern coast of Iceland, illustrating the maxim that nature abhors a vacuum. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... World map showing the equator in red The Equator is an imaginary circle drawn around a planet (or other astronomical object) at a distance halfway between the poles. ...


The air is drawn into the intertropical convergence zone by the action of the Hadley cell, a macroscale atmospheric feature which is part of the Earth's heat and moisture distribution system. It is transported aloft by the convective activity of thunderstorms; regions in the intertropical convergence zone receive precipitation more than 200 days in a year. The Hadley cell is a circulation pattern that dominates the tropical atmosphere, with rising motion near the equator, poleward flow 10-15 kilometers above the surface, descending motion in the subtropics, and equatorward flow near the surface. ... Spatial scale provides a shorthand form for discussing relative lengths, areas, distances and sizes. ... Layers of Atmosphere (NOAA) Air redirects here. ... Convection is the internal movement of currents within fluids (i. ... A shelf cloud associated with a heavy or severe thunderstorm over Enschede, The Netherlands. ...

Contents

Position

The location of the intertropical convergence zone varies over time. Over land, it moves back and forth across the equator following the sun's zenith point. Over the oceans, where the convergence zone is better defined, the seasonal cycle is more subtle, as the convection is constrained by the distribution of ocean temperatures. In broad terms, the zenith is the direction pointing directly above a particular location (perpendicular, orthogonal). ...


Sometimes, a double ITCZ forms, with one located north and another south of the equator. When this occurs, a narrow ridge of high pressure forms between the two convergence zones, one of which is usually stronger than the other.

Vertical velocity at 500 hPa, July average. Ascent (negative values) is a tracer for the ITCZ and is concentrated close to the solar equator; descent (positive values) is more diffuse.
Vertical velocity at 500 hPa, July average. Ascent (negative values) is a tracer for the ITCZ and is concentrated close to the solar equator; descent (positive values) is more diffuse.

Image File history File links Omega-500-july-era40-1979. ... Image File history File links Omega-500-july-era40-1979. ...

Effects on weather

Variation in the location of the intertropical convergence zone drastically affects rainfall in many equatorial nations, resulting in the wet and dry seasons of the tropics rather than the cold and warm seasons of higher latitudes. Longer term changes in the intertropical convergence zone can result in severe droughts or flooding in nearby areas. One of the most influential doctrines in history is that all humans are divided into groups called nations. ...


Within the ITCZ the average winds are slight, unlike the zones north and south of the equator where the trade winds feed in. Early sailors named this belt of calm the doldrums because of the inactivity and stagnation they found themselves in after days of no wind.[1] To find oneself becalmed in this region in a hot and muggy climate could mean death in an era when wind was the only major motive force. The trade winds are a pattern of wind found in bands around the Earths equatorial region. ...


Role in tropical cyclone formation

Tropical cyclogenesis depends upon low-level vorticity as one of its six requirements, and the ITCZ/monsoon trough fill this role as it is a zone of wind change and speed, otherwise known as horizontal wind shear. As the ITCZ migrates more than 500 km from the equator during the respective hemisphere's summer season, increasing coriolis force allows the formation of tropical cyclones within this zone more possible. In the north Atlantic and the northeastern Pacific oceans, tropical waves move along the axis of the ITCZ causing an increase in thunderstorm activity, and under weak vertical wind shear, these clusters of thunderstorms can become tropical cyclones. Global Tropical Cyclone Tracks Cyclogenesis is the technical term describing the development or strengthening of a surface low pressure system, or cyclone, in the atmosphere. ... Wind shear is a difference in wind speed or direction between two points in the atmosphere. ... In physics, the Coriolis effect is an inertial force first described by Gaspard-Gustave Coriolis, a French scientist, in 1835. ... This article is about weather phenomena. ... Tropical waves, also known as easterly waves, are elongated areas of relatively low air pressure, oriented north to south, causing areas of cloudiness and thunderstorms. ... Wind shear is a difference in wind speed or direction between two points in the atmosphere. ... This article is about weather phenomena. ...


See also

Horse latitudes or Subtropical High are subtropical latitudes between 30 and 35 degrees both north and south, characterized by light winds and hot, dry weather, caused by descending air. ... The Glossary of Meteorology defines a monsoon trough simply: A line in a weather map showing the locations of minimum sea level pressure in a monsoon region. ... Global Tropical Cyclone Tracks Cyclogenesis is the technical term describing the development or strengthening of a surface low pressure system, or cyclone, in the atmosphere. ...

References

  • Short NASA article with high resolution photo

  Results from FactBites:
 
7(p) Global Scale Circulation of the Atmosphere (1740 words)
The intertropical convergence zone is identified on the figures by a red line.
In January, the intertropical convergence zone is found south of the equator (Figure 7p-4).
Note that the line representing the intertropical convergence zone is not straight and parallel to the lines of latitude.
  More results at FactBites »

 
 

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