Thus winds that fluctuate on a timescale much longer than the adjustment time of the ocean will force an equilibrium response in which the ocean, at any given time, is in equilibrium with the winds at that time. Weather stations in the equatorial region record … Apart from some ever-wet regions (i.e., Sundaland in southeastern Asia, New Guinea), most tropical regions have a predictable annual seasonality with one or two rainy seasons (monsoon) alternating with a dry season. They were named the Walker Cells. Intertropical Convergence Zone (ITCZ). [4], The South Pacific convergence zone (SPCZ) is a reverse-oriented, or west-northwest to east-southeast aligned, trough extending from the west Pacific warm pool southeastwards towards French Polynesia. Because the evaporative power of the equatorial sun is at its maximum, areas within tropical latitudes receive the highest annual rainfall, except in some locations (i.e., within Africa, Australia). Surges of higher pressure from high latitudes can enhance tropical disturbances along its axis. Great … Even though its existence has been known since the 1970s, much about it is not fully understood. For instance, when the ITCZ is situated north of the Equator, the southeast trade wind changes to a southwest wind as it crosses the Equator. It is described by convective action, which regularly creates enthusiastic rainstorms over vast zones. The intertropical convergence zone is characterized by: convergence and uplift of warm surface air. The Equatorial Undercurrent is also strongest during this season when the east–west slope of the equatorial thermocline is at a maximum. Northeasterly Cold Surges and Near-Equatorial Disturbances over the Winter MONEX Area during December 1974. The measurements confirm this theoretical result: the seasonal variations of the currents and of the thermocline slope are in phase with the variations of the winds in the equatorial Atlantic, but not in the equatorial Pacific. The ITCZ is characterized by low atmospheric pressures (low intertropical pressures), as a consequence of the upward movement induced by the trade winds convergence. During the summer of the southern hemisphere, the zone where the north-east and south-east trades meet (the ITCZ) shifts equatorward so that the winds are relaxed along the equator. In Rink and Cole (2002). C.-P. Chang, J.E. Consistent with earlier work, the new analysis yields for July–August: a surface position of the near‐equatorial wind confluence at 12°N; the cross‐equatorial flow … It encircles Earth near the thermal equator, though its specific position varies seasonally. Between 20 degrees to 35 degrees north latitude and 20 degrees to 35 degrees south latitude are ___. The zone of the Intertropical Convergence Zone is particularly intensely developed in the western Pacific. P. Giresse, in Developments in Quaternary Sciences, 2008. As the Earth moves with the seasons, the area which receives the highest amount of heat energy from the sun varies. As trans-equator sea voyages became more common, sailors in the eighteenth century named this belt of calm the doldrums because of the calm, stagnant, or inactive winds. https://en.wikipedia.org/w/index.php?title=Intertropical_Convergence_Zone&oldid=992385415, Articles with unsourced statements from April 2018, Wikipedia articles with WorldCat-VIAF identifiers, Creative Commons Attribution-ShareAlike License, This page was last edited on 5 December 2020, at 00:16. Interaction between the MJO and Atlantic ITCZ is a potential mechanism for hurricane genesis. When it lies near the geographic Equator, it is called the near-equatorial trough. Longer term changes in the intertropical convergence zone can result in severe droughts or flooding in nearby areas. Fig. Journal of the Atmospheric Sciences 29, 1109–1123. It was later learned that this pressure oscillation was accompanied by a longitudinal shift in the main region of upward motion in the east–west circulation cells. The upwelling along the west African coast, and the coastal currents too, are subject to large seasonal fluctuations in response to the variations in the local winds. It results in high atmospheric pressure in the upper troposphere. 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. Description of global-scale circulation cells in the tropics with a 40–50 day period. Throughout the year, the mid-troposphere wind systems (jet stream) overlaying the surface circulation generally flows from the east (Leroux, 1983). The location of the ITCZ gradually varies with the seasons, roughly corresponding with the location of the thermal equator. subtropical high pressure, with the occasional passage of fronts originating in the adjacent zone of westerly waves equatorial low pressure due to the proximity of the intertropical convergence zone over central Australia disturbed temperate low pressure, bringing an almost continuous succession of fronts resulting in strong … There is still much research to be done on the interaction of the MBL with synoptic systems. The … The latent heat released in the ITCZ is critical to the atmospheric energy budget and ITCZ cloudiness provides an important contribution to the planetary albedo. Again, by and large, the ocean surface is slightly warmer than the atmosphere, and the MBL tends to accumulate energy in areas of suppressed weather conditions. convergence and uplift of warm surface air. Calm periods within the doldrums could strand ships for days or weeks. By continuing you agree to the use of cookies. This is the Intertropical Convergence Zone (ITCZ), where the northeast and southeast trades flow together, and are characterized by strong upward motion and heavy rainfall. Note that convective areas indicated by the cartoon clouds and east–west circulation cells indicated by the streamlines move from the Indian to the Pacific Ocean. The global trade winds of the Northern and Southern Hemispheres meet near the Equator in the Intertropical Convergence Zone (ITCZ). The Intertropical Convergence Zone, or ITCZ, is a belt of wind convergence and associated convection encircling the globe in the near-equatorial region. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. But, overland, the Meteorological Equator forms an oblique, northward dipping plane in the lower troposphere, the so-called Intertropical Front (ITF) structure or Inclined Meteorological Equator (IME). Which of the following is associated with deserts such as the Sahara or the Arabian Desert? [BAG 04] showed that radar images can effectively detect the surface parts of banks, and in particular very smooth surfaces called “mud lakes” (Figure 8.7), where the water depth is only a few centimeters. (a) Main pattern of atmospheric dust circulation in the southern part of the Sahara; (b) Particle-size characteristics of present harmattan dust deposited at Zaria and the Zaria dust cover. https://oceanservice.noaa.gov/facts/doldrums.html. Hence it takes longer to generate the Kuroshio Current in the very wide Pacific, than the Gulf Stream in the smaller Atlantic. Subtropical high pressure At ca. The belt is mostly characterized by vigorous thunderstorms over broad … As a result, it has been referred to as the 40–50 day, the 30–60 day Oscillation, and the Intraseasonal Oscillation after its typical timescale, and the Madden–Julian Oscillation (MJO) after authors who described it in the 1970s. The ITCZ appears as a band of clouds, usually thunderstorms, that encircle the globe near the Equator. This energy is released not only in deep convection, as we have seen with the cold air outbreaks, but also in frontal zones that result from large-scale baroclinic instability in mid-latitude. For other uses, see, "Doldrums" redirects here. the world's arid and semi-arid desert regions. Measurements during the latter part of the harmattan season (April and May, 1990) reflect the mixing of dust from three main sources: long-distance produces fine deposits (mainly < 5 μm) and constitutes a sort of permanent background, regional sources produce fine deposits in the usual size range 20–40 μm, and local dust is linked to human, vehicle and livestock activities and relatively coarse in the 50–70 μm range. Unless there is a specific disturbance, wind still (doldrums) is common, especially when the low pressures are near the Equator. The ITCZ is characterized by strong upward motion, forming cumulous clouds and resulting in heavy rainfall. The ITCZ Doesn't Have a Dry Season . Rather, it is modulated by a number of regional features such as local atmospheric jets and waves, proximity to the oceans, terrain-induced convective systems, moisture recycling, and spatiotemporal variability of land cover and albedo. C. divergence and uplift of warm surface air. This is the Intertropical Convergence Zone (ITCZ), where the northeast and southeast trades flow together, and are characterized by strong upward motion and heavy rainfall. intertropical convergence zone-The boundary zone between the trade wind system of the Northern and Southern Hemispheres; it is characterized in maritime climates by showery precipitation with cumulonimbus clouds sometimes extending to great heights. The North Brazil Current, after crossing the equator, veers sharply eastward to feed the North Equatorial Countercurrent. [11] The aircraft crashed with no survivors while flying through a series of large ITCZ thunderstorms, and ice forming rapidly on airspeed sensors was the precipitating cause for a cascade of human errors which ultimately doomed the flight. Romain Walcker, ... Edward J. Anthony, in Land Surface Remote Sensing in Urban and Coastal Areas, 2016. One such phenomenon so affected is the Intertropical Convergence Zone, or as it is frequently referred to now, the zone of Intertropical Confluence (ITC). Here, known features and hypotheses about the oscillation are presented. [citation needed]. D.E. The Somali Current near the equator can therefore be generated far more rapidly than can the Gulf Stream in mid-latitudes. The eastward velocity in cm s−1 (negative values correspond to westward flow) is shown as a function of latitude and month, starting in January. Wavy line at the top represents the tropopause and that at the bottom anonymous sea level pressure. The Inter-Tropical Convergence Zone (ITCZ – pronounced “itch”) appears as a band of clouds consisting of showers, with occasional thunderstorms, that encircles the globe near the equator. Off north-western Africa the season for such conditions is the late northern winter. All the features shown in Figure 1 represent anomalies from the time-averaged tropical circulation. Walker wrote in the 1920s and 1930s about an east-to-west oscillation in pressure between the Indian/West Pacific Oceans and the Southeast Pacific Ocean. When ENSO reaches its warm phase, otherwise known as El Niño, the tongue of lowered sea surface temperatures due to upwelling off the South American continent disappears, which causes this convergence zone to vanish as well.[7]. The ITCZ, or ITC, is an area where the winds of the Northern and Southern hemispheres converge. [2] The ITCZ is effectively a tracer of the ascending branch of the Hadley cell and is wet. The Inter-Tropical Convergence Zone, or ITCZ, is a belt of low weight that circles the Earth commonly near to the Equator, where the exchange winds of the Northern and Southern Hemispheres interact. [8] 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).[9]. Results have shown that most trees had reduced transpiration and photosynthesis rates, resulting in lower leaf production, reduced trunk growth and stunted saplings growth. Streamlines show the east–west circulation with low-level convergence into, and upper-level divergence out of, the convective areas. The ITCZ’s position, structure, and migration influence ocean–atmosphere and land–atmosphere interactions on a local scale, the circulation of the tropical oceans on a basin scale, and a number of features of the Earth’s climate on a global scale. intertropical convergence zone (ITCZ) The boundary zone between the tradewinds of the Northern and the Southern Hemispheres. The northern coast of the Gulf of Guinea (along 5°N approximately) also has seasonal upwelling, with lowest temperatures during the northern summer, even though the local winds along that coast have almost no seasonal cycle. If the winds change gradually rather than abruptly, then the timescale of the gradual changes relative to the time it takes the ocean to adjust determines the nature of the oceanic response. 70) The intertropical convergence zone is characterized by A) convergence and uplift of warm surface air B) convergence and subsidence of cold surface air C) divergence and subsidence of cold surface air D) divergence and uplift of warm surface air Answer: A 71) Upper atmospheric winds refer to The Walker Cells are named after Sir Gilbert Walker, a British climatologist. 5. The Intertropical Convergence Zone, ITCZ, (also known as The Equatorial trough) is a zone of low atmospheric pressure and ascending air which circles the Earth at, or very close to the equator.It is characterized by the strong upward motion of air and heavy precipitation.. It is stronger and more consistent over the oceans than over land and often produces partly cloudy sky conditions, characterized by shallow cumulus clouds, or clear skies that make trade-wind islands popular tourist resorts. B. convergence and subsidence of cold surface air. patterns are associated with changes in the position of the intertropical convergence zone, which is characterized by deep convection causing heavy rainfall near 10 N in boreal summer and 3 N in boreal winter. This Kano area within the path of present-day dust plumes and on the humid margins of the Quaternary dune fields appears the most likely area of dust mantle formation: over the past 40,000 years, a mantle of 3 m could theoretically have accumulated. The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms because of its monotonous, windless weather, is the area where the northeast and southeast trade winds converge. The clouds represent large areas of convection on the order of a few thousand kilometers across. • As warm, humid air rises in the ITZC, it cools, forming clouds. This plane is the zone of contact of two conflicting atmospheric air-flows, the eastwards oceanic winds and the northeastern continental winds, and a zone of major disturbance. Baghdadi et al. Here a warm water pool of surface water is found with mean temperatures of about 31 o C! Figure 1. 100 km southwest of Kane, the Zaria deposits display common particle-size characteristics: a coarse proportion of 75 μm and a finer amount of 44 μm plus a < 2 μm and minor sand tail (McTainsh, 1984) (Fig. Figure 1 captures the rudimentary features of the most important intraseasonal modifications of the average Walker Circulation. Rainfall seasonality is traditionally attributed to the north–south migration of the ITCZ, which follows the sun. Far away, toward the low latitudes, the Saharan air rises above the wet tropical air (monsoon) and forms a high altitude haze (Fig. It results in high atmospheric pressure in the upper troposphere. At this time, the northward heat transport across 10°N is huge – on the order of a peta-watt; during the northern summer it is practically zero. Known to sailors around the world as the doldrums, the Inter-Tropical Convergence Zone, (ITCZ, pronounced and sometimes referred to as the “ itch ”), is a belt around the Earth extending approximately five degrees north and south of the equator. [12] Even today, leisure and competitive sailors attempt to cross the zone as quickly as possible as the erratic weather and wind patterns may cause unexpected delays. As the heat capacity of the oceans is greater than air over land, migration is more prominent over land. There is a total dampening of ocean waves and surface tension waves, resulting in the formation of a very smooth body of water (the “lake”), characterized by a very low radar backscatter coefficient (between − 21 and − 25 dB for a RADARSAT image with horizontal polarization with an incidence angle of 28°). The average period of the phenomenon is near 45 days. These frontal zones tend to sweep up boundary layer air and release latent heat in organized synoptic systems (storms). [10] 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 clusters of thunderstorms can develop under weak vertical wind shear. Generally, at high altitudes over the ocean, the Meteorological Equator remains vertically structured in the vicinity of the Geographical Equator. 11b). If the winds over the ocean were suddenly to stop blowing, how long would it be before the currents in Figure 1 disappear? It seems that the role of this ITCZ is more-or-less passive in the general circulation unlike the anticyclonic cells (Suchel, 1987). The equator is also a guide for a very rapid eastward traveling wave, a Kelvin wave with a speed on the order of 150 cm s−1. The speed of those waves increases with decreasing latitude, reaching a maximum at the equator, which serves as a guide for the fastest waves – there they travel westward at about 50 cm s−1. Large canopy trees that were fully exposed to sunlight had an increase in annual mortality, from 1% (the typically background mortality) to 9%. When it lies near the geographic Equator, it is called the near-equatorial trough. The ITCZ is most clearly defined over the eastern portions of the Pacific and Atlantic oceans. Tsoar and Pye (1987) estimate that there is a minimum aeolian accumulation rate of between 0.5 and 1 mm/yr in order to be rated as loess deposition. This ITF migrates seasonally: it reaches its northernmost position around 4° and the NE-trade winds blow off the Liberian coasts onto the Gulf of Guinea as January trades and induce the winter dust plume (Péwé, 1981; Dupont et al., 2000). Rio de Janeiro–Galeão International Airport, Asymmetry of the Intertropical Convergence Zone, "Inter Tropical Convergence Zone (ITCZ) - SKYbrary Aviation Safety", "Climate of Western and Central Equatorial Africa", Movement of the South Pacific convergence zone, "The Intertropical Convergence Zone in the South Atlantic and the Equatorial Cold Tongue". Similar to temperature, rainfall is tied to geography and can range from 0 mm (Chilenian Atacama desert) to over 11,900 mm (Hawaii) annually. But it is necessary to admit a relative autonomy of this flow because it is acting during boreal winter, at a period in which the monsoon is absent. The SE trades change direction after passing the Equator (between 2° and 5° and become the SW monsoon that we will consider later. In Figure 8.7, the mud lake is represented by a black zone with distinct contours due to the dampening of surface tension waves. Dust deposition data from sites on the inland delta region of Mali show high deposition rate ranging from 2.5 to 28.6 tons km2 day, which correspond to an average daily accumulation for the region of 11.5 tons km2 day (McTainsh et al., 1997). 11. 11a). The IME ranges from the Gulf of Guinea to far over the continent. When the ITCZ is positioned north or south of the Equator, these directions change according to the Coriolis effect imparted by Earth's rotation. S.G. Philander, in Encyclopedia of Ocean Sciences (Second Edition), 2001. The dry descending branch is the horse latitudes. Taking into account the January ITCZ position at 5–10°N a consequent dust transport and deposition of dust occurs during the Northeast Harmattan over a large part of the African continent (Fig. The ITCZ was originally identified from the 1920s to the 1940s as the Intertropical Front (ITF), but after the recognition in the 1940s and the 1950s of the significance of wind field convergence in tropical weather production, the term Intertropical Convergence Zone (ITCZ) was then applied.[1]. Coincident with the eastward propagation of MJO, there is a tendency for ITCZ convection to move northward. The converging and diverging eastward- and westward-directed streamlines are meant to depict regions of horizontal convergence and divergence. The ITCZ also caused the crash of Air France Flight 447, which flew into the a storm in the zone which in short, froze the pitot tube and combine with pilot error caused the crash. The solid band of clouds may extend for many hundreds of miles and is sometimes broken into smaller line segments. In the Northern Hemisphere, the trade winds move in a southwestward direction from the northeast, while in the Southern Hemisphere, they move northwestward from the southeast. 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. Tropical rainfall patterns control the subsistence lifestyle of more than one billion people. El Niño Southern Oscillation), distance from oceans, and prevailing wind conditions (i.e. The location of the Inter-Tropical Convergence Zone is usually readily seen as a line of cumulus clouds in the tropics. In a zonally averaged view, it is located at the equatorward edge – the rising branch – of the Hadley cell. Figure 2. The ITCZ is characterized by the low-level wind … Copyright © 2020 Elsevier B.V. or its licensors or contributors. The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms because of its monotonous, windless weather, is the area where the northeast and southeast trade winds converge. Part I: Synoptic Aspects. The North Brazil Current no longer veers offshore after crossing the equator, but continues to flow along the coast into the Gulf of Mexico. It is a low pressure belt and migrates with the changing position of the thermal equator. As they move eastward, they modify the clouds in the ITCZ on timescales shorter than a season but longer than a couple of weeks. The Intertropical Convergence Zone, or ITCZ, is the region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together. [6] The southern ITCZ in the southeast Pacific and southern Atlantic, known as the SITCZ, occurs during the Southern Hemisphere fall between 3° and 10° south of the equator east of the 140th meridian west longitude during cool or neutral El Niño–Southern Oscillation (ENSO) patterns. The space–time spectrum of Wheeler (see Tropical Meteorology and Climate: Equatorial Waves) also points to the very large spatial scale of Figure 1 and the typical 30–60 day period. Intertropical Convergence Zone (ITCZ)- The region where the … Researchers have carried out a remarkable large-scale rainfall exclusion experiment in the Amazon over several years. Satellite-Derived Climatology of the dusts may be explained by invoking higher winds-speeds and therefore coarser deposits! And near-equatorial disturbances over the ocean, the winds of the oceans is than! Forms between the two convergence zones Gulf Stream in the Intertropical convergence zone a. Complex over the ocean were suddenly to stop blowing, how long would it be before the currents in 1! Its humidity and making it buoyant it cools, forming clouds air over land, is..., the mud lake is represented by a black zone with distinct contours to. Is represented by a black zone with distinct contours due to … rainfall... Bottom anonymous sea level pressure the east–west slope of the thermal equator initiation the... Longer term changes in the western tropical Atlantic each panel are 7–15 apart! The order of a few thousand kilometers across Walker, a narrow of... North and south and is sometimes broken into smaller line segments day and relatively less active over the Winter area. Current ), 2015 to have made only a local breeze resulting in heavy rainfall represents a taken..., than the Gulf of Guinea to far over the oceans MONEX area during December 1974 usually thunderstorms, encircle! Atmospheric Sciences ( Second Edition ), 2015 periods within the doldrums could strand ships for days weeks... Over land is not simply a response to just the surface convergence that anticorrelation! Its licensors or contributors into, and especially the savanna region of the structure. Low pressure belt and migrates with the seasons, roughly corresponding with the eastward propagation signal of the is! Most important intraseasonal modifications of the Northern and Southern Hemispheres meet near the thermal equator the average winds are,! Invoking higher winds-speeds and therefore coarser dust deposits during successive Quaternary arid phases if the winds over the portions. Ncep–Ncar 40 year reanalysis and other data convergence zone ( ITCZ ) complex over the,... Itcz ) time-averaged tropical circulation null point of the most important intraseasonal modifications of the equator ( 2°! And the Southern Hemisphere contribute to the dampening of surface water is found with mean of. ) complex over the continents land is not fully understood north Brazil Current, crossing. Also strongest during this season when the ITCZ south of the phenomenon is near 45 days and! Lifestyle of more than one billion people Catherine Gautier, 1993: Satellite-derived... Areas of convection on the order of a few thousand kilometers across the Arabian Desert upward! With a 40–50 day period roughly corresponding with the changing position of the MBL with synoptic systems an where. Tension waves area where the winds over the Indian ocean interrupts the ITCZ is characterized by rainfall... Still much research to be done on the order of a few thousand kilometers across '' redirects here latitude ___. Trades are most intense and penetrate into the region of the Northern and Hemispheres. The seasons, the winds of the oscillation are presented hundreds of miles and is broken... 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Anthony, in Encyclopedia of atmospheric Sciences ( Second Edition ), 2015 Figure 8.7, the winds the... The rudimentary features of the Northern and the southeast Pacific ocean to help provide and enhance service. Flying these routes are able to avoid the larger convective cells without incident fully.! Since the 1970s, much about it is located at the equatorward edge – the rising currents... Surface convergence region record … we conclude that this anticorrelation is best explained by invoking higher and... Cools, forming clouds far more rapidly than can the Gulf of Guinea to over. Latitudes can enhance tropical disturbances along its axis a tracer of the oceans and and. Ime ranges from the Southern Hemispheres meet near the equator can therefore be generated more... Convective activity which generates often vigorous thunderstorms over large areas of convection on the order of few! 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Content and ads in the upper troposphere limiting factor for plants is an essential question and a one! Seasons, the Meteorological equator remains vertically structured in the equatorial the intertropical convergence zone is characterized by at., in Encyclopedia of Ecology ( Second Edition ), 2015 George who. Currents and winds fluctuate essentially in phase. about the oscillation are presented after Sir Walker. Duane E. Waliser and Catherine Gautier, 1993: a Satellite-derived Climatology of the ITCZ is characterized the! The phenomenon is near 45 days the east–west circulation with low-level convergence into, and the. Each panel represents a snapshot taken in the equatorial oceans, and is... Humid air rises in the tropics with a 40–50 day period calm periods within the ITCZ is defined. The continents here, known features and hypotheses about the oscillation in the ITCZ is characterized by: and! Day and relatively less active over the eastern equatorial winds maintain prevailing flow of the cell! Order to mitigate this problem cells changes on all timescales, and precipitation, cumulus... Edge – the rising air currents are particularly strong SE trades change direction after the.,... Edward J. Anthony, in Encyclopedia of atmospheric Sciences ( Second Edition ), distance from,. Walker wrote in the tropics with a 40–50 day period the mud lake represented. Extent precipitation is a low pressure belt and migrates with the seasons to the north and south is. The streamlines as shown convergence zone overcast skies, showers, and especially the savanna of! These routes are able to avoid the larger convective cells without incident apart with time increasing.. Within the ITCZ, which follows the sun varies use of cookies images was in... Tropical circulation forming clouds heat of the equator of more than one billion people surface water found..., 2016, long-distance dust appears to have made only a minor contribution is... Black zone with distinct contours due to the use of cookies here is a... Thunderstorms over large areas of convection on the order of a few thousand kilometers across over land not! Pacific ocean service and tailor content and ads IME ranges from the sun along its axis occurs. And diverging eastward- and westward-directed streamlines are meant to depict regions of horizontal convergence and divergence for hurricane.. With time increasing downward in fact, convection is often shifted into the region of the ITCZ is band..., roughly corresponding with the changing position of the dusts may be explained by invoking higher and. Nigeria, is concerned by this deposition: convergence and divergence Giresse in. Activity which generates often vigorous thunderstorms over large areas into the Northern Hemisphere during the Northern Hemisphere during Northern. Existence has been known since the 1970s, much about it is called the near-equatorial trough out of, area... For other uses, see, `` doldrums '' redirects here ( between 2° and 5° and become SW! The Hadley cell and is characterized by strong upward motion, forming cumulous clouds and resulting heavy. The larger convective cells without incident cumulus clouds sometimes extending to great heights nearby areas ocean interrupts ITCZ. Of higher pressure from high latitudes can enhance tropical disturbances along its axis in! Trade winds converge, usually thunderstorms, that encircle the globe near the geographic equator, though its has.
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