"Doldrums The doldrums is a colloquial expression derived from historical maritime usage, which refers to those parts of the Atlantic Ocean and the Pacific Ocean affected by a low-pressure area around the equator where the prevailing winds are calm. The doldrums are also noted for calm periods when the winds disappear altogether, trapping sailing ships for periods of days or weeks. The term appears to have arisen in the eighteenth century, when trans-equator sailing voyages became more common. Since this zone is where two trade winds meet, it is also called the Intertropical Convergence Zone. They roughly lie between latitudes"
"known as the trade winds. As these inwards flows of air converge they reduce horizontal wind speed, and as they rise, they form precipitation. The vertical convection also results in a net export of heat and freshwater from the lower atmosphere into the troposphere This system is known as the ITCZ. The location of the ITCZ is centred on the areas of highest insolation, although it is more stationary over the oceans than landmasses. In the Atlantic region, the ITCZ is clearly developed, and the spatial extent of the ITCZ reaches a minimum close to the equator during the boreal"
"the intertropical convergence zone can result in severe droughts or flooding in nearby areas. In some cases, the ITCZ may become narrow, especially when it moves away from the equator; the ITCZ can then be interpreted as a front along the leading edge of the equatorial air. There appears to be a 15 to 25-day cycle in thunderstorm activity along the ITCZ, which is roughly half the wavelength of the Madden–Julian oscillation (MJO). Within the ITCZ the average winds are slight, unlike the zones north and south of the equator where the trade winds feed. Early sailors named this belt"
"Trade winds The trade winds are the prevailing pattern of surface winds from the east toward the west (easterly) found in the tropics, within the lower portion of the Earth's atmosphere, in the lower part of the troposphere near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere, strengthening during the winter and when the Arctic oscillation is in its warm phase. Trade winds have been used by captains of sailing ships to cross the world's oceans for centuries, and enabled colonial expansion into the Americas"
"lie near the average latitude of the subtropical ridge, where descent reduces the relative humidity of the air mass. The strongest winds are in the mid-latitudes where cold polar air meets warm air from the tropics. The trade winds (also called trades) are the prevailing pattern of easterly surface winds found in the tropics towards the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over the world's oceans. Trade winds also steer African"
"Northern Hemisphere converge with the south-east trades of the Southern Hemisphere. This area is known as the Inter-Tropical Convergence Zone (ITCZ). On satellite Images the ITCZ is mostly seen as a long band of clouds in the Equatorial region, the main effect of the ITCZ is the creation of dry and rainy seasons in the Equatorial area. The Mulanje Massif, because its unique position as a “mountain island” rising more than 2,500 metres above the surrounding plains is strongly affected by the ITCZ, acting as a rain barrier. This becomes very visible when comparing the annual normal rainfalls, on and"
"northerly winds blow down the Irish Sea. They can also be associated with sea breeze fronts. Convergence zone A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. This causes a mass accumulation that eventually leads to a vertical movement and to the formation of clouds and precipitation. Large-scale convergence, called synoptic-scale convergence, is associated with weather systems such as baroclinic troughs, low-pressure areas, and cyclones. Small-scale convergence will give phenomena from isolated cumulus clouds to large areas of thunderstorms. The inverse of a convergence is"
"develop over oceans (maritime), and travel northward on the western periphery of the subtropical ridge. Maritime tropical air masses are sometimes referred to as trade air masses. The one region of the Earth which has an absence of trade winds is the north Indian ocean. Clouds which form above regions within trade wind regimes are typically composed of cumulus which extend no more than in height, and are capped from being taller by the trade wind inversion. Trade winds originate more from the direction of the poles (northeast in the Northern Hemisphere, southeast in the Southern Hemisphere) during the cold"
"to as trade air masses. Maritime tropical air masses that effect the United States originate in the Caribbean Sea, southern Gulf of Mexico, and tropical Atlantic east of Florida through the Bahamas. Monsoon air masses are moist and unstable. Superior air masses are dry, and rarely reach the ground. They normally reside over maritime tropical air masses, forming a warmer and drier layer over the more moderate moist air mass below, forming what is known as a trade wind inversion over the maritime tropical air mass. Continental Polar air masses (cP) are air masses that are cold and dry due"
"Monsoon trough The monsoon trough is a portion of the Intertropical Convergence Zone in the Western Pacific, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and northern hemispheres. Westerly monsoon winds lie in its equatorward portion while easterly trade winds exist poleward of the trough. Right along its axis, heavy rains can be found which usher in the peak of a location's respective rainy season. As it passes poleward of a location, hot and dry conditions develop."
"and trade routes to become established across the Atlantic and Pacific oceans. In meteorology, the trade winds act as the steering flow for tropical storms that form over the Atlantic, Pacific, and southern Indian Oceans and make landfall in North America, Southeast Asia, and Madagascar and eastern Africa, respectively. Trade winds also transport African dust westward across the Atlantic Ocean into the Caribbean Sea, as well as portions of southeastern North America. Shallow cumulus clouds are seen within trade wind regimes, and are capped from becoming taller by a trade wind inversion, which is caused by descending air aloft from"
"surface winds found in the tropics near the Earth's equator, equatorward of the subtropical ridge. These winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. The trade winds act as the steering flow for tropical cyclones that form over world's oceans, guiding their path westward. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean sea, as well as portions of southeast North America. The westerlies or the prevailing westerlies are the prevailing winds in the middle latitudes (i.e., between 35 and 65 degrees latitude), which blow"
"the Aw climate zone are typically deciduous and placed in the Tropical dry forest biome: with further transitional zones (ecotones) of savannah woodland then tropical and subtropical grasslands, savannas, and shrublands. Seasonal (mixed) tropical forests can be found in many parts of the tropical zone, with examples found in: The climate of seasonal forests is typically controlled by a system called the Intertropical Convergence Zone (ITCZ) located near the equator and created by the convergence of the trade winds from the Northern and Southern Hemispheres. The position of these bands vary seasonally, moving north in the northern summer and south"
"in Africa. There is a large variability in the dust transport to the Caribbean and Florida from year to year. Dust events have been linked to a decline in the health of coral reefs across the Caribbean and Florida, primarily since the 1970s. Trade winds The trade winds are the prevailing pattern of surface winds from the east toward the west (easterly) found in the tropics, within the lower portion of the Earth's atmosphere, in the lower part of the troposphere near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the"
"Convergence zone A convergence zone in meteorology is a region in the atmosphere where two prevailing flows meet and interact, usually resulting in distinctive weather conditions. This causes a mass accumulation that eventually leads to a vertical movement and to the formation of clouds and precipitation. Large-scale convergence, called synoptic-scale convergence, is associated with weather systems such as baroclinic troughs, low-pressure areas, and cyclones. Small-scale convergence will give phenomena from isolated cumulus clouds to large areas of thunderstorms. The inverse of a convergence is a divergence. An example of a convergence zone is the Intertropical Convergence Zone (ITCZ), a low"
"Equatorial Countercurrent. Tropical instability waves Tropical instability waves, often abbreviated TIW, are a phenomenon in which the interface between areas of warm and cold sea surface temperatures near the equator form a regular pattern of westward-propagating waves. These waves are often present in the Atlantic Ocean, extending westward from the African coast, but are more easily recognizable in the Pacific, extending westward from South America. They have an average period of about 30 days and wavelength of about 1100 kilometers, and are largest in amplitude between June and November. They are also largest during La Niña conditions, and may disappear"
"near the Intertropical convergence zone from tropical waves. The Coriolis force is usually too weak to initiate sufficient rotation near the equator. Storms frequently form in the warm waters of the Gulf of Mexico, the Caribbean Sea, and the tropical Atlantic Ocean as far east as the Cape Verde Islands, the origin of strong and long-lasting Cape Verde-type hurricanes. Systems may also strengthen over the Gulf Stream off the coast of the eastern United States, wherever water temperatures exceed . Although most storms are found within tropical latitudes, occasionally storms will form further north and east from disturbances other than"
"Tropical instability waves Tropical instability waves, often abbreviated TIW, are a phenomenon in which the interface between areas of warm and cold sea surface temperatures near the equator form a regular pattern of westward-propagating waves. These waves are often present in the Atlantic Ocean, extending westward from the African coast, but are more easily recognizable in the Pacific, extending westward from South America. They have an average period of about 30 days and wavelength of about 1100 kilometers, and are largest in amplitude between June and November. They are also largest during La Niña conditions, and may disappear when strong"
"with the location of the thermal equator. As the heat capacity of the oceans is greater than air over land, migration is more prominent over land. 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. Sometimes, a double ITCZ forms, with one located north and another south of the Equator, one of which is usually stronger than the other. When this occurs, a narrow ridge of high pressure forms between the two convergence zones. The South Pacific convergence zone (SPCZ) is a"
"and possibly ammonium hydrosulfide. The clouds are located in the tropopause and are arranged into bands of different latitudes, known as tropical regions. These are sub-divided into lighter-hued ""zones"" and darker ""belts"". The interactions of these conflicting circulation patterns cause storms and turbulence. Wind speeds of 100 m/s (360 km/h) are common in zonal jets. The zones have been observed to vary in width, color and intensity from year to year, but they have remained sufficiently stable for scientists to give them identifying designations. The cloud layer is only about deep, and consists of at least two decks of clouds:"
"Tropical Atlantic Variability The Tropical Atlantic Variability (TAV) is influenced by internal interaction and external effects. TAV can be discussed in different time scales: seasonal (annual cycle) and interannual. Seasonal variability is the dominant time scale of TAV, which is due to the seasonal march of the sun. This seasonal variability is related to the movement of intertropical convergence zone (ITCZ),which is the convergent zone of trade winds from south and north near the equator. It has strong vertical convection resulting to a redundant participation band and weak winds. The mean location of the ITCZ over the Atlantic Ocean is"
"between 0°–20° to the right of the wind in the northern hemisphere and the helix forming bands of divergence and convergence at the surface. At the convergence zones, there are commonly concentrations of floating seaweed, foam and debris along these bands. Along these divergent zones, the ocean surface is typically clear of debris since diverging currents force material out of this zone and into adjacent converging zones. At the surface the circulation will set a current from the divergence zone to the convergence zone and the spacing between these zones are of the order of . Below convergence zones narrow"
"the city block the westerly winds driven by the Intertropical Convergence Zone which throughout the year, owing to the Humboldt Current off the west coast of South America, remains centred in the north of the continent at Quibdó’s longitudes. The result is that the extremely unstable ascending air from the Intertropical Convergence Zone is consistently forced to rise over the Chocó plain and as it cools it gives up enormous quantities of moisture. What is more, due to the exuberant nature and biodiversity in the region, a biotic pump phenomena causes the Choco low-level-jet as another important factor in driving"
"in the western side of the basin near Brazil, when they have sustained wind speeds of at least 65 km/h (40 mph), the generally accepted minimum sustained wind velocity for a disturbance to be designated as a tropical storm in the North Atlantic basin. Below is a list of notable South Atlantic tropical and subtropical cyclones. Until April 1991, it was thought that tropical cyclones did not develop within the South Atlantic. Very strong vertical wind shear in the troposphere is considered a deterrent. The Intertropical Convergence Zone drops one to two degrees south of the equator, not far enough"
"Just as the temperature of the ocean surface varies comparatively little from season to season, so also does the temperature of air that has moved great distances across the ocean; the air brings with it to the land the mild temperature regime characteristic of the surrounding ocean. In the central North Pacific, the trade winds represent the outflow of air from the great region of high pressure, the North Pacific High, typically located well north and east of the Hawaiian Islands. The Pacific High, and with it the trade-wind zone, moves north and south with changing angle of the sun,"
"and along low pressure zones of surface tropospheric convergence which encircle the Earth close to the equator and near the 50th parallels of latitude in the northern and southern hemispheres. The adiabatic cooling processes that lead to the creation of clouds by way of lifting agents are all associated with convergence; a process that involves the horizontal inflow and accumulation of air at a given location, as well as the rate at which this happens.<ref name=""Convergence/divergence""></ref> Near the equator, increased cloudiness is due to the presence of the low-pressure Intertropical Convergence Zone (ITCZ) where very warm and unstable air promotes"
"South Pacific high, creating a dry and cold wind. This effect is more prominent in the winter months, when the intensity of the cold is more stronger. The Intertropical convergence zone reaches the region during the summer months, leading to low pressure, and unstable air masses due to the relatively high land temperatures compared to the sea during this season. This leads to enhanced precipitation in the form of convective thunderstorms during the summer months. During the winter months, the intertropical convergence zone moves northwards to Ecuador while both the South Pacific and South Atlantic high move northwards, and the"
"many decades for the correct theory to become accepted, and even today Hadley's theory can still be encountered occasionally, particularly in popular books and websites. Hadley's theory was the generally accepted theory long enough to make his name become universally attached to the circulation pattern in the tropical atmosphere. In 1980 Isaac Held and Arthur Hou developed the Held-Hou Model to describe the Hadley circulation. The region in which the equatorward moving air masses converge and rise, is known as the intertropical convergence zone, or ITCZ. Within that zone develops a band of thunderstorms that produce high-precipitation. Having lost most"
"within the subtropical ridge. The weaker the trade winds become, the more rainfall can be expected in the neighboring landmasses. The term ""trade winds"" originally derives from the early fourteenth century late Middle English word ""trade,"" meaning ""path"" or ""track."" The Portuguese recognized the importance of the trade winds (then the ""Volta do mar"", meaning in Portuguese ""turn of the sea"" but also ""return from the sea"") in navigation in both the north and south Atlantic ocean as early as the 15th century. From West Africa, the Portuguese had to sail away from continental Africa, that is, to west and"
"experiences inward blowing winds because winds are moving air blowing outwards from regions of high pressure to regions of low pressure. The Tropical Maritime Airmass is a warm humid and unstable trade wind due to its warmth. Convectional currents are easily set up within the airmass whenever there is little instability in the airmass as a result of a slight to a very high orographic uplift in mountainous regions like the obudu plateau or the heating of the land which can trigger the formation of cumulonimbus cloud leading to thunderstorms within the airmass. During the dominance of the Tropical Maritime"
"South Atlantic Convergence Zone The South Atlantic convergence zone, or SACZ, is an elongated axis of clouds, precipitation, and convergent winds oriented in a northwest-southeast manner across southeast Brazil into the southwest Atlantic Ocean. By definition, the feature is a monsoon trough. It is strongest in the warm season. Thunderstorm activity along the feature magnifies over three or more days when the Madden–Julian oscillation passes into the region, due to the enhanced upper divergence. Low level winds over Rondônia are tied to the strength of this zone, where westerly wind anomalies correlate to active phases of the South American monsoon,"
"Finally, the Humboldt Current or the Peru Current flows west along the coast of South America from Peru to Chile and extends up to 1,000 kilometers offshore. These four eastern boundary currents comprise the majority of coastal upwelling zones in the oceans. Upwelling at the equator is associated with the Intertropical Convergence Zone (ITCZ) which actually moves, and consequently, is often located just north or south of the equator. Easterly (westward) trade winds blow from the Northeast and Southeast and converge along the equator blowing West to form the ITCZ. Although there are no Coriolis forces present along the equator,"
"using uncoupled atmospheric models with prescribed sea surface temperatures, and those 3 models each with differing complexity showed less severe double ITCZ bias than the ensemble of coupled models. At its southeast edge, the circulation around the feature forces a salinity gradient in the ocean, with fresher and warmer waters of the western Pacific lying to its west. Cooler and saltier waters lie to its east. Tropical textbook : from trade winds to cyclone (2 vol), 897 pp., Florent Beucher, 25 mai 2010, Météo-France, South Pacific convergence zone The South Pacific Convergence Zone (SPCZ), a reverse-oriented monsoon trough, is a"