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48-451: The earliest mention of Taoudenni is by al-Sadi, in his Tarikh al-Sudan , who wrote that in 1586 when Moroccan forces attacked the salt mining center of Taghaza (150 km north west of Taoudenni) some of the miners moved to 'Tawdani'. In 1906 the French soldier Édouard Cortier visited Taoudenni with a unit of the camel corps ( méharistes ) and published the first description of the mines. At

96-559: A consistent global displacement of the ITCZ under anthropogenic climate change. In contrast, most of the same simulations show narrowing and intensification under the same prescribed conditions. However, simulations in Coupled Model Intercomparison Project Phase 6 (CMIP6) have shown greater agreement over some regional shifts of the ITCZ in response to anthropogenic climate change, including a northward displacement over

144-514: A dozen have names. They include: Taoudenni is a remote site in the hottest region on the planet, located over a hundred and sixty kilometres from the nearest inhabited location of any size. The region is located in the middle of the Sahara Desert , in the southern part of the Tanezrouft (one of the harshest areas on the planet, known for extreme heat and aridity), and features an extreme version of

192-440: 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. 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 . It lies just south of

240-433: A prison were built at Taoudenni in 1969 during the regime of Moussa Traoré . The prison was used to detain political prisoners until 1988, when it was closed. Many of the prisoners were government officials who had been accused of plotting against the regime. The prisoners worked in the salt mines and many of them died. To the east of the ruins of the prison building is a cemetery containing 140 individual graves, of which only

288-461: A tracer of the ascending branch of the Hadley cell and is wet. The dry descending branch is the horse latitudes . The location of the ITCZ gradually varies with the seasons, roughly corresponding 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,

336-566: Is also located in one of the driest regions on the globe. Tarikh al-Sudan The Tarikh al-Sudan ( Arabic : تاريخ السودان Tārīkh as-Sūdān ; also Tarikh es-Sudan , "History of the Sudan ") is a West African chronicle written in Arabic in around 1655 by the chronicler of Timbuktu, al-Sa'di. It provides the single most important primary source for the history of the Songhay Empire . It and

384-425: Is cut into irregular slabs that are around 110 cm x 45 cm by 5 cm in thickness and weigh around 30 kg. Two of the high quality layers are of sufficient thickness to be split in half, so that 5 slabs can be produced from the three layers. Having removed the salt from the base area of the pit, the miners excavate horizontally to create galleries from which additional slabs can be obtained. As each pit

432-408: Is exhausted another is dug, so there are now thousands of pits spread over a wide area. Over the centuries salt has been extracted from three distinct areas of the depression, with each successive area located further to the south west. The three areas can be seen clearly on satellite photographs. At the time of Édouard Cortier's visit in 1906 the mining area was 3 km south of the ksar; in the 1950s

480-512: Is sometimes referred to as a monsoon trough (a usage that is more common in Australia and parts of Asia). 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 )

528-409: Is that for each four slabs transported to Timbuktu, one is for the miners and the other three are payment for the camel owners. Up to the middle of the 20th century the salt was transported in two large camel caravans ( azalaï ), one leaving Timbuktu in early November and a second leaving Timbuktu in late March, at the end of the season. Horace Miner, an American anthropologist who spent seven months in

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576-484: The Age of Sail , to find oneself becalmed in this region in a hot and muggy climate could mean death when wind was the only effective way to propel ships across the ocean. Calm periods within the doldrums could strand ships for days or weeks. 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. In 2009, thunderstorms along

624-501: The Coriolis effect imparted by Earth's rotation . 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. The ITCZ is formed by vertical motion largely appearing as convective activity of thunderstorms driven by solar heating, which effectively draw air in; these are the trade winds. The ITCZ is effectively

672-582: The Tarikh al-fattash , another 17th century chronicle giving a history of Songhay, are together known as the Timbuktu Chronicles . The author, Abderrahmane al-Sa'di, was born on 28 May 1594, and died at an unknown date sometime after 1655-56, the last date to be mentioned in his chronicle. He spent most of his life working for the Moroccan Arma bureaucracy, initially in the administration of Djenné and

720-404: The doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal equator though its specific position varies seasonally. When it lies near the geographic Equator , it is called the near-equatorial trough . Where the ITCZ is drawn into and merges with a monsoonal circulation, it

768-528: The hot desert climate ( Köppen climate classification BWh ). The region features a torrid, hyper-arid climate with unbroken sunshine all year long. Averages high temperatures exceed 40 °C (104 °F) from April to September and reach an extreme peak of 47.9 °C (118.2 °F) in July, the highest value for such an elevation above sea level. Winters are also very warm compared to the world average. High temperatures average close to 27 °C (80.6 °F) in

816-625: The British government. During his stay in Gwandu (now in northwest Nigeria) he consulted a copy of the Tarikh al-Sudan in his investigation of the history of the Songhay empire. However he was under the misapprehension that the author was the Timbuktu scholar Ahmed Baba . In his book Barth wrote: But I myself was so successful as to have an opportunity of perusing a complete history of the kingdom of Songhay, from

864-588: The Indian Ocean and eastern Africa and a southward displacement over the eastern Pacific and Atlantic oceans. The doldrums are notably described in Samuel Taylor Coleridge 's poem The Rime of the Ancient Mariner (1798) and also provide a metaphor for the initial state of boredom and indifference of Milo, the child hero of Norton Juster 's classic 1961 children's novel The Phantom Tollbooth . It

912-509: The Intertropical Convergence Zone played a role in the loss of Air France Flight 447 , which crashed while flying from Rio de Janeiro–Galeão International Airport to Charles de Gaulle Airport near Paris . 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

960-604: The Northern Hemisphere based on results from climate models ; a northward rebound began subsequently following forced changes in the gradient in temperature between the Northern and Southern hemispheres. These fluctuations in ITCZ positioning had robust effects on climate; for instance, displacement of the ITCZ may have led to drought in the Sahel in the 1980s. Atmospheric convection may become stronger and more concentrated at

1008-622: 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. 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. Variation in

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1056-508: The Southern Hemisphere Hadley cell. The ITCZ shifted north during the mid-Holocene but migrated south following changes in insolation during the late-Holocene towards its current position. The ITCZ has also undergone periods of contraction and expansion within the last millennium. A southward shift of the ITCZ commencing after the 1950s and continuing into the 1980s may have been associated with cooling induced by aerosols in

1104-420: The active mines were located in an area 5 km from the ksar, while the current mines are at a distance of 9 km. In 2007-2008 there were around 350 teams of miners, with each team usually consisting of an experienced miner with 2 labourers, giving a total of around 1000 men. The men live in primitive huts constructed from blocks of inferior quality salt and work at the mines from October to April, avoiding

1152-633: The center of the ITCZ in response to a globally warming climate, resulting in sharpened contrasts in precipitation between the ITCZ core (where precipitation would be amplified) and its edges (where precipitation would be suppressed). Atmospheric reanalyses suggest that the ITCZ over the Pacific has narrowed and intensified since at least 1979, in agreement with data collected by satellites and in-situ precipitation measurements. The drier ITCZ fringes are also associated with an increase in outgoing longwave radiation outward of those areas, particularly over land within

1200-583: The coolest month. The mean annual daily temperature is around 29 °C (84.2 °F) and the annual average high is 37.8 °C (100.0 °F), one of the highest in the world. The annual average rainfall is between 1 cm (0.39 in) and 2 cm (0.78 in) which mainly falls from July to September because of the Intertropical Convergence Zone 's influence on its climate. On average, Taoudenni sees 3,700 hours of bright sunshine annually, with 84% of daytime hours being sunny. The site

1248-522: The copy had been made. Houdas published the Arabic text in 1898 and a translation into French in 1900. A century later John Hunwick published a partial translation into English. Manuscripts A, B and C were used by Houdas. A further four were listed by Hunwick. The text of the manuscripts are all very similar. The differences are mainly in the spelling of places and personal names. The Berber author of Ta'rikh al-Sudan , Abd al-Rahman al-Sa'di, recorded

1296-538: The date – year, month and day – of Ahmed Baba's death is mentioned by the author ...". Dubois realized that the manuscript was by Abd al-Sadi. After the French occupation of Mali in the 1890s, two copies of the manuscript were acquired by the Bibliothèque Nationale in Paris. These were studied by the Arabic scholar Octave Houdas. The undated Manuscript A had been sent by Louis Archinard , Manuscript B

1344-402: The eighteenth century named this belt of calm the doldrums because of the calm, stagnant, or inactive winds. Tropical cyclogenesis depends upon low-level vorticity as one of its six requirements, and the ITCZ fills this role as it is a zone of wind change and speed, otherwise known as horizontal wind shear . As the ITCZ migrates to tropical and subtropical latitudes and even beyond during

1392-489: The equator during the Southern Hemisphere warm season, but can be more extratropical in nature, especially east of the International Date Line . It is considered the largest and most important piece of the ITCZ, and has the least dependence upon heating from a nearby land mass during the summer than any other portion of the monsoon trough . The southern ITCZ in the southeast Pacific and southern Atlantic, known as

1440-507: 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. As trans-equator sea voyages became more common, sailors in

1488-510: The flight. Most aircraft flying these routes are able to avoid the larger convective cells without incident. Based on paleoclimate proxies , the position and intensity of the ITCZ varied in prehistoric times along with changes in global climate . During Heinrich events within the last 100 ka, a southward shift of the ITCZ coincided with the intensification of the Northern Hemisphere Hadley cell coincident with weakening of

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1536-410: The hottest months of the year, when only about 10 of them remain. The slabs are transported across the desert via the oasis of Araouane to Timbuktu . In the past they were always carried by camel, but recently some of the salt has been moved by four-wheel drive trucks. By camel the journey to Timbuktu takes around three weeks, with each camel carrying either four or five slabs. The typical arrangement

1584-418: 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. In some cases, the ITCZ may become narrow, especially when it moves away from

1632-618: The massina region of the Inland Niger Delta . In 1646 he became chief secretary to the Arma administration of Timbuktu . The early sections of the chronicle are devoted to brief histories of earlier Songhay dynasties, of the Mali Empire and of the Tuareg , and to biographies of the scholars and holymen of both Timbuktu and Djenné. The main part of the chronicle covers the history of the Songhay from

1680-465: The mid-latitudes and the subtropics . This change in the ITCZ is also reflected by increasing salinity within the Atlantic and Pacific underlying the ITCZ fringes and decreasing salinity underlying central belt of the ITCZ. The IPCC Sixth Assessment Report indicated "medium agreement" from studies regarding the strengthening and tightening of the ITCZ due to anthropogenic climate change. Less certain are

1728-517: The middle of the 15th century till the Moroccan invasion in 1591, and then the history of Timbuktu under Moroccan rule up to 1655. Al-Sadi rarely acknowledges his sources. For the earlier period much of his information is presumably based on oral tradition. From around 1610 the information would have been gained first hand. In 1853 the German scholar and explorer Heinrich Barth visited Timbuktu on behalf of

1776-667: The oral tradition surrounding the origin of the Mali . He states, "Mali is the name of an extensive territory lying in the far west (of the Sudan) to the direction of the Ocean. It was Kaya-Magha who founded the first kingdom in that region. Their subjects, however, were Wa'kore ( Soninke ). When their kingdom came to an end, the people of Mali succeeded to hegemony." Intertropical Convergence Zone The Intertropical Convergence Zone ( ITCZ / ɪ tʃ / ITCH , or ICZ ), known by sailors as

1824-519: The regional and global shifts in ITCZ position as a result of climate change, with paleoclimate data and model simulations highlighting contrasts stemming from asymmetries in forcing from aerosols, volcanic activity, and orbital variations , as well as uncertainties associated with changes in monsoons and the Atlantic meridional overturning circulation . The climate simulations run as part of Coupled Model Intercomparison Project Phase 5 (CMIP5) did not show

1872-477: The respective hemisphere's summer season, increasing Coriolis force makes the formation of tropical cyclones within this zone more possible. Surges of higher pressure from high latitudes can enhance tropical disturbances along its axis. 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. In

1920-399: 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 ITCZ is commonly defined as an equatorial zone where

1968-583: The time the only building was the Ksar de Smida, which had a surrounding wall with a single small entrance on the western side. The ruins of the ksar are 600 m north of the prison building. The Taoudenni mines are located on the bed of an ancient salt lake . The miners use crude axes to dig pits, which usually measure 5 m by 5 m with a depth of 4 m. The miners first remove 1.5 m of red clay overburden, then several layers of poor quality salt before reaching three layers of high quality salt. The salt

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2016-424: The town, estimated that in 1939-40 the winter caravan consisted of more than 4,000 camels and that the total production amounted to 35,000 slabs of salt. Jean Clauzel records that the number of slabs reaching Timbuktu increased from 10,515 in 1926 to 160,000 (4800 t) in 1957–1958. However, in the early 1970s the production decreased, and at the end of the decade was between 50,000 and 70,000 slabs. A military post and

2064-406: The trade winds converge. Rainfall seasonality is traditionally attributed to the north–south migration of the ITCZ, which follows the sun. Although this is largely valid over the equatorial oceans, the ITCZ and the region of maximum rainfall can be decoupled over the continents. The equatorial precipitation over land is not simply a response to just the surface convergence. Rather, it is modulated by

2112-399: The universal statement of the learned people of Negroland, were written by a distinguished person of the name of A'hmed Baba, although in the work itself that individual is only spoken of in the third person; and it would seem that additions had been made to the book by another hand; but on this point I can not speak with certainty, as I had not sufficient time to read over the latter portion of

2160-541: The very dawn of historical records down to the year 1640 of our era; although, unfortunately, circumstances prevented my bringing back a complete copy of this manuscript, which forms a respectable quarto volume, and I was only able, during the few days that I had this manuscript in my hands during my stay in Gandó, to make short extracts of those passages from its contents which I thought of the highest interest in an historical and geographical point of view. These annals, according to

2208-515: The work with the necessary attention and care. Forty years later the French journalist Félix Dubois in his Timbuctoo the Mysterious pointed out that the Tarikh could not have been written by Ahmed Baba as it mentions Ahmed Baba's death. "How could a man so well informed in Arabian subjects be so completely deceived? ... If he had read the entire book with more attention, he would have seen that

2256-505: Was a copy made for Félix Dubois while in Djenné in 1895 and was very similar to Manuscript A. A third copy of the Tarikh al-Sudan , Manuscript C, was sent to Houdas by the linguist René Basset who was head of the École Supérieure des Lettres in Algiers . Manuscript C was generally superior to the other two and included vowels for many of the proper names and the date of 1792 for when

2304-523: Was then applied. The ITCZ appears as a band of clouds, usually thunderstorms, that encircle the globe near the Equator. 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. When the ITCZ is positioned north or south of the Equator, these directions change according to

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