1.
West Africa
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West Africa, also called Western Africa and the West of Africa, is the westernmost subregion of Africa. Early human settlers from northern Holocene societies arrived in West Africa around 12,000 B. C, sedentary farming began in, or around the fifth millennium B. C, as well as the domestication of cattle. By 1500 B. C, ironworking technology allowed an expansion of productivity. Northern tribes developed walled settlements and non-walled settlements that numbered at 400, in the forest region, Iron Age cultures began to flourish, and an inter-region trade began to appear. The desertification of the Sahara and the change of the coast cause trade with upper Mediterranean peoples to be seen. Local leather, cloth, and gold also contributed to the abundance of prosperity for many of the following empires. Also, based on the archaeology of city of Kumbi Saleh in modern-day Mauritania, three great kingdoms were identified in Bilad al-Sudan by the ninth century. They included Ghana, Gao and Kanem, the Sosso Empire sought to fill the void, but was defeated by the Mandinka forces of Sundiata Keita, founder of the new Mali Empire. In the 15th century, the Songhai would form a new dominant state based on Gao, in the Songhai Empire, under the leadership of Sonni Ali, further east, Oyo arose as the dominant Yoruba state and the Aro Confederacy as a dominant Igbo state in modern-day Nigeria. The Kingdom of Nri was a West African medieval state in the present-day southeastern Nigeria, the Kingdom of Nri was unusual in the history of world government in that its leader exercised no military power over his subjects. The kingdom existed as a sphere of religious and political influence over a third of Igboland, the Eze Nri managed trade and diplomacy on behalf of the Nri people, and possessed divine authority in religious matters. The Oyo Empire was a Yoruba empire of what is today Western, established in the 15th century, the Oyo Empire grew to become one of the largest West African states. It rose through the organizational skills of the Yoruba, wealth gained from trade. The Benin Empire was an empire located in what is now southern Nigeria. Its capital was Edo, now known as Benin City, Edo and it should not be confused with the modern-day country called Benin, formerly called Dahomey. The Benin Empire was one of the oldest and most highly developed states in the hinterland of West Africa. Olfert Dapper, a Dutch writer, describing Benin in his book Description of Africa and its craft was the most adored and treasured bronze casting in the history of Africa. It was annexed by the British Empire in 1897 during the invasion, in the early 19th century, a series of Fulani reformist jihads swept across Western Africa
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Nigeria
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Its coast in the south lies on the Gulf of Guinea in the Atlantic Ocean. It comprises 36 states and the Federal Capital Territory, where the capital, Nigeria is officially a democratic secular country. Modern-day Nigeria has been the site of numerous kingdoms and tribal states over the millennia, the modern state originated from British colonial rule beginning in the 19th century, and the merging of the Southern Nigeria Protectorate and Northern Nigeria Protectorate in 1914. The British set up administrative and legal structures whilst practising indirect rule through traditional chiefdoms, Nigeria became a formally independent federation in 1960, and plunged into a civil war from 1967 to 1970. Nigeria is often referred to as the Giant of Africa, owing to its large population, with approximately 184 million inhabitants, Nigeria is the most populous country in Africa and the seventh most populous country in the world. Nigeria has one of the largest populations of youth in the world, Nigeria is divided roughly in half between Christians, who live mostly in the southern part of the country, and Muslims in the northern part. A minority of the population practise religions indigenous to Nigeria, such as native to the Igbo. As of 2015, Nigeria is the worlds 20th largest economy, worth more than $500 billion and $1 trillion in terms of nominal GDP and it overtook South Africa to become Africas largest economy in 2014. The 2013 debt-to-GDP ratio was 11 percent, Nigeria is a member of the MINT group of countries, which are widely seen as the globes next BRIC-like economies. It is also listed among the Next Eleven economies set to become among the biggest in the world, Nigeria is a founding member of the African Union and a member of many other international organizations, including the United Nations, the Commonwealth of Nations and OPEC. The name Nigeria was taken from the Niger River running through the country and this name was coined in the late 19th century by British journalist Flora Shaw, who later married Lord Lugard, a British colonial administrator. The origin of the name Niger, which applied only to the middle reaches of the Niger River, is uncertain. The word is likely an alteration of the Tuareg name egerew n-igerewen used by inhabitants along the middle reaches of the river around Timbuktu prior to 19th-century European colonialism. The Nok civilisation of Northern Nigeria flourished between 500 BC and AD200, producing life-sized terracotta figures which are some of the earliest known sculptures in Sub-Saharan Africa, further north, the cities Kano and Katsina have a recorded history dating to around 999 AD. Hausa kingdoms and the Kanem-Bornu Empire prospered as trade posts between North and West Africa, the Kingdom of Nri of the Igbo people consolidated in the 10th century and continued until it lost its sovereignty to the British in 1911. Nri was ruled by the Eze Nri, and the city of Nri is considered to be the foundation of Igbo culture, Nri and Aguleri, where the Igbo creation myth originates, are in the territory of the Umeuri clan. Members of the clan trace their lineages back to the patriarchal king-figure Eri, in West Africa, the oldest bronzes made using the lost-wax process were from Igbo Ukwu, a city under Nri influence. The Yoruba kingdoms of Ife and Oyo in southwestern Nigeria became prominent in the 12th and 14th centuries, the oldest signs of human settlement at Ifes current site date back to the 9th century, and its material culture includes terracotta and bronze figures
3.
Border
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Borders are geographic boundaries of political entities or legal jurisdictions, such as governments, sovereign states, federated states, and other subnational entities. Some borders—such as an internal administrative border, or inter-state borders within the Schengen Area—are often open. Other borders are partially or fully controlled, and may be crossed only at designated border checkpoints. Mostly contentious, borders may even foster the setting up of buffer zones, a difference has also been established in academic scholarship between border and frontier, the latter denoting a state of mind rather than state boundaries. In the past, many borders were not clearly defined lines, instead there were often intervening areas often claimed, a special case in recent times was the neutral zones that were set up along parts of Saudi Arabias borders with Kuwait and Iraq. In modern times, marchlands have been replaced by clearly defined and demarcated borders, for the purposes of border control, airports and seaports are also classed as borders. Most countries have some form of control to regulate or limit the movement of people, animals. Some borders require presentation of legal paperwork like passports and visas, or other identity documents, moving goods across a border often requires the payment of excise tax, often collected by customs officials. Animals moving across borders may need to go into quarantine to prevent the spread of infectious diseases. Most countries prohibit carrying illegal drugs or endangered animals across their borders, moving goods, animals, or people illegally across a border, without declaring them or seeking permission, or deliberately evading official inspection, constitutes smuggling. Controls on car liability insurance validity and other formalities may also take place, in places where smuggling, migration, and infiltration are a problem, many countries fortify borders with fences and barriers, and institute formal border control procedures. But some borders are merely signposted and this is common in countries within the European Schengen Area and on rural sections of the Canada–United States border. Borders may even be unmarked, typically in remote or forested regions. The frontiers were particularly porous for the movement of migrants. A border may have been, Agreed by the countries on both sides Imposed by the country on one side Imposed by third parties, e. g, in addition, a border may be a de facto military ceasefire line. Political borders are imposed on the world through human agency, political borders are often classified by whether or not they follow conspicuous physical features on the earth. Natural borders are geographical features that present natural obstacles to communication, existing political borders are often a formalization of these historical, natural obstacles. Some geographical features that often constitute natural borders are, Oceans, oceans create very costly natural borders, very few nation-states span more than one continent
4.
Benin
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Benin, officially the Republic of Benin and formerly Dahomey, is a country in West Africa. It is bordered by Togo to the west, Nigeria to the east, the majority of its population lives on the small southern coastline of the Bight of Benin, part of the Gulf of Guinea in the northernmost tropical portion of the Atlantic Ocean. The capital of Benin is Porto-Novo, but the seat of government is in Cotonou, Benin covers an area of 114,763 square kilometers and its population in 2015 was estimated to be approximately 10.88 million. Benin is a nation, highly dependent on agriculture, with substantial employment. The official language of Benin is French, however, indigenous languages such as Fon and Yoruba are commonly spoken. The largest religious group in Benin is Roman Catholicism, followed closely by Islam, Vodun and this region was referred to as the Slave Coast from as early as the 17th century due to the large number of slaves shipped to the New World during the Trans-Atlantic slave trade. After slavery was abolished, France took over the country and renamed it French Dahomey, in 1960, Dahomey gained full independence from France, and had a tumultuous period with many different democratic governments, many military coups and military governments. A Marxist–Leninist state called the Peoples Republic of Benin existed between 1975 and 1990, in 1991, it was replaced by the current multi-party Republic of Benin. During the colonial period and at independence, the country was known as Dahomey, on 30 November 1975 it was renamed to Benin, after the body of water on which the country lies—the Bight of Benin—which, in turn, had been named after the Benin Empire. The country of Benin has no connection to Benin City in modern Nigeria, the form Benin is the result of a Portuguese corruption of the city of Ubinu. The new name, Benin, was chosen for its neutrality, the current country of Benin combines three areas which had different political and ethnic systems prior to French colonial control. Before 1700, there were a few important city states along the coast, the situation changed in the 1600s and early 1700s as the Kingdom of Dahomey, which was of Fon ethnicity, was founded on the Abomey plateau and began taking over areas along the coast. The Dahomey Kingdom was known for its culture and traditions, young boys were often apprenticed to older soldiers, and taught the kingdoms military customs until they were old enough to join the army. This emphasis on preparation and achievement earned Dahomey the nickname of black Sparta from European observers. The kings of Dahomey sold their war captives into transatlantic slavery, by about 1750, the King of Dahomey was earning an estimated £250,000 per year by selling Africans to the European slave-traders. Court protocols, which demanded that a portion of war captives from the many battles be decapitated, decreased the number of enslaved people exported from the area. The number went from 102,000 people per decade in the 1780s to 24,000 per decade by the 1860s, the decline was partly due to the banning of the trans-Atlantic slave trade by Britain and other countries. This decline continued until 1885, when the last slave ship departed from the coast of the present-day Benin Republic bound for Brazil, a former Portuguese colony, the capitals name Porto-Novo is of Portuguese origin, meaning New Port
5.
Chad
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Chad, officially the Republic of Chad, is a landlocked country in Central Africa. It is bordered by Libya to the north, Sudan to the east and it is the fifth largest country in Africa in terms of area. Chad has several regions, a zone in the north, an arid Sahelian belt in the centre. Lake Chad, after which the country is named, is the largest wetland in Chad, the capital NDjamena is the largest city. Chads official languages are Arabic and French, Chad is home to over 200 different ethnic and linguistic groups. The religions of Chad are Islam, followed by Christianity, beginning in the 7th millennium BC, human populations moved into the Chadian basin in great numbers. France conquered the territory by 1920 and incorporated it as part of French Equatorial Africa, in 1960, Chad obtained independence under the leadership of François Tombalbaye. Resentment towards his policies in the Muslim north culminated in the eruption of a civil war in 1965. In 1979 the rebels conquered the capital and put an end to the souths hegemony, however, the rebel commanders fought amongst themselves until Hissène Habré defeated his rivals. He was overthrown in 1990 by his general Idriss Déby, since 2003 the Darfur crisis in Sudan has spilt over the border and destabilised the nation, with hundreds of thousands of Sudanese refugees living in and around camps in eastern Chad. Unsustainable high birth rates and a lack of agriculture let the country persist in poverty, while many political parties are active, power lies firmly in the hands of President Déby and his political party, the Patriotic Salvation Movement. Chad remains plagued by violence and recurrent attempted coups détat. Chad is one of the poorest and most corrupt countries in the world, since 2003 crude oil has become the countrys primary source of export earnings, superseding the traditional cotton industry. In the 7th millennium BC, ecological conditions in the half of Chadian territory favored human settlement. Some of the most important African archaeological sites are found in Chad, mainly in the Borkou-Ennedi-Tibesti Region, for more than 2,000 years, the Chadian Basin has been inhabited by agricultural and sedentary people. The region became a crossroads of civilizations, the earliest of these were the legendary Sao, known from artifacts and oral histories. The Sao fell to the Kanem Empire, the first and longest-lasting of the empires that developed in Chads Sahelian strip by the end of the 1st millennium AD, two other states in the region, Baguirmi and Wadai Empire emerged in the 16th and 17th centuries. The power of Kanem and its successors was based on control of the trade routes that passed through the region
6.
Cameroon
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Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It is bordered by Nigeria to the west, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, Cameroons coastline lies on the Bight of Biafra, part of the Gulf of Guinea and the Atlantic Ocean. French and English are the languages of Cameroon. The country is referred to as Africa in miniature for its geological and cultural diversity. Natural features include beaches, deserts, mountains, rainforests, the country is well known for its native styles of music, particularly makossa and bikutsi, and for its successful national football team. Early inhabitants of the territory included the Sao civilisation around Lake Chad, portuguese explorers reached the coast in the 15th century and named the area Rio dos Camarões, which became Cameroon in English. Fulani soldiers founded the Adamawa Emirate in the north in the 19th century, Cameroon became a German colony in 1884 known as Kamerun. After World War I, the territory was divided between France and the United Kingdom as League of Nations mandates, the Union des Populations du Cameroun political party advocated independence, but was outlawed by France in the 1950s, leading to the Cameroonian Independence War. It waged war on French and UPC militant forces until 1971, in 1960, the French-administered part of Cameroon became independent as the Republic of Cameroun under President Ahmadou Ahidjo. The southern part of British Cameroons federated with it in 1961 to form the Federal Republic of Cameroon, the federation was abandoned in 1972. The country was renamed the United Republic of Cameroon in 1972, Cameroon enjoys relatively high political and social stability. This has permitted the development of agriculture, roads, railways, nevertheless, large numbers of Cameroonians live in poverty as subsistence farmers. Power lies firmly in the hands of the president since 1982, Paul Biya. The English-speaking territories of Cameroon have grown increasingly alienated from the government, politicians and civil society in English-speaking regions have called for greater decentralization and even complete separation or independence from the former French-governed territories. The territory of present-day Cameroon was first settled during the Neolithic Era, the longest continuous inhabitants are groups such as the Baka. From here, Bantu migrations into eastern, southern, and central Africa are believed to have originated about 2,000 years ago, the Sao culture arose around Lake Chad c. AD500 and gave way to the Kanem and its successor state, kingdoms, fondoms, and chiefdoms arose in the west. Portuguese sailors reached the coast in 1472 and they noted an abundance of the ghost shrimp Lepidophthalmus turneranus in the Wouri River and named it Rio dos Camarões, which became Cameroon in English
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Niger
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Niger, officially the Republic of Niger, is a landlocked country in Western Africa, named after the Niger River. Niger is bordered by Libya to the northeast, Chad to the east, Nigeria and Benin to the south, Burkina Faso and Mali to the west, and Algeria to the northwest. Niger covers a area of almost 1,270,000 km2, making it the largest country in West Africa. The countrys predominantly Islamic population of about 19 million is mostly clustered in the far south, the capital city is Niamey, located in the far-southwest corner of Niger. Niger is a country, and is consistently one of the lowest-ranked in the United Nations Human Development Index. Much of the portions of the country are threatened by periodic drought. The economy is concentrated around subsistence and some export agriculture clustered in the fertile south. Nigerien society reflects a diversity drawn from the long independent histories of its ethnic groups and regions. Historically, what is now Niger has been on the fringes of large states. Since independence, Nigeriens have lived under five constitutions and three periods of military rule, following a military coup in 2010, Niger has become a democratic, multi-party state. A majority live in areas, and have little access to advanced education. Early human settlement in Niger is evidenced by archaeological remains. In prehistoric times, the climate of the Sahara was wet and provided favorable conditions for agriculture, in 2005–06, a graveyard in the Tenere desert was discovered by Paul Sereno, a paleontologist from the University of Chicago. His team discovered 5, 000-year-old remains of a woman and two children in the Tenere Desert, the evidence along with remains of animals that do not typically live in desert are among the strongest evidence of the green Sahara in Niger. It is believed that progressive desertification around 5000 BCE pushed sedentary populations to the south and south-east. By at least the 5th century BCE, Niger became an area of trade, led by the Berber tribes from the north. This trade has made Agadez a pivotal place of the trans-Saharan trade and this mobility, which would continue in waves for several centuries, was accompanied with further migration to the south and interbreeding between southern black and northern white populations. It was also aided by the introduction of Islam to the region at the end of the 7th century, several empires and kingdoms also flourished during this era up to the beginning of colonization in Africa
8.
Gulf of Guinea
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The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian is in the gulf, among the many rivers that drain into the Gulf of Guinea are the Niger and the Volta. The coastline on the gulf includes the Bight of Benin and the Bight of Bonny, the Niger River in particular deposited organic sediments out to sea over millions of years which became crude oil. The origin of the name Guinea is thought to be an area in the region, bovill gives a thorough description, The name Guinea is usually said to have been a corrupt form of the name Ghana, picked up by the Portuguese in the Maghrib. The present writer finds this unacceptable, the name Guinea has been in use both in the Maghrib and in Europe long before Prince Henrys time. A passage in Leo points to Guinea having been a form of Jenne, less famous than Ghana but nevertheless for many centuries famed in the Maghrib as a great market. The relevant passage reads, The Kingdom of Ghinea. called by the merchants of our nation Gheneoa, by the inhabitants thereof Genni and by the Portugals. But it seems probable that Guinea derives from aguinaou, the Berber for Negro. Marrakech has a gate, built in the century, called the Bab Aguinaou. The modern application of the name Guinea to the coast dates only from 1481, the name Guinea is still attached to the names of three countries in Africa, Guinea, Guinea-Bissau, and Equatorial Guinea, as well as New Guinea in Melanesia. The main river shedding its waters in the gulf is the Niger River, the Gulf of Guinea contains a number of islands, the largest of which are in a southwest-northeast chain, forming part of the Cameroon line of volcanoes. Annobón, also known as Pagalu or Pigalu, is an island that is part of Equatorial Guinea, bobowasi Island is an island off the west coast of Africa in the Gulf of Guinea that is part of Western region Ghana. Bioko is an island off the west coast of Africa in the Gulf of Guinea that is part of Equatorial Guinea, corisco is an island belonging to Equatorial Guinea. Elobey Grande and Elobey Chico are two small islands belonging to Equatorial Guinea, São Tomé and Príncipe is a Portuguese-speaking island nation in the Gulf of Guinea that became independent from Portugal in 1975. It is located off the western equatorial coast of Africa and consists of two islands, São Tomé and Príncipe and they are located about 140 kilometres apart and about 250 and 225 kilometres, respectively, off the northwestern coast of Gabon. Both islands are part of a volcanic mountain range. São Tomé, the southern island, is situated just north of the Equator. Media related to Gulf of Guinea at Wikimedia Commons The Gulf of Guinea Commission - CGG - GGC
9.
Lake Chad
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Lake Chad is a historically large, shallow, endorheic lake in Africa, which has varied in size over the centuries. Lake Chad is economically important, providing water to more than 68 million people living in the four countries surrounding it on the edge of the Sahara Desert and it is the largest lake in the Chad Basin. Lake Chad is mainly in the far west of Chad, bordering on northeastern Nigeria, the Chari River, fed by its tributary the Logone, provides over 90% of the lakes water, with a small amount coming from the Yobe River in Nigeria/Niger. Despite high levels of evaporation, the lake is fresh water, over half of the lakes area is taken up by its many small islands, reedbeds and mud banks, and a belt of swampland across the middle divides the northern and southern halves. The shorelines are largely composed of marshes, because Lake Chad is very shallow—only 10.5 metres at its deepest—its area is particularly sensitive to small changes in average depth, and consequently it also shows seasonal fluctuations in size. Lake Chad has no apparent outlet, but its waters percolate into the Soro, the climate is dry most of the year, with moderate rainfall from July through September. Lake Chad gave its name to the country of Chad, the name Chad is a local word meaning large expanse of water, in other words, a lake. Lake Chad is the remnant of an inland sea, paleolake Mega-Chad. At its largest extent the river Mayo Kébbi represented the outlet of the paleolake Mega-Chad, connecting it to the Niger River, the presence of African manatees in the inflows of Lake Chad is an evidence of that history. Romans reached the lake in the first century of their empire, indeed during Augustus times lake Chad was still a huge lake and two Roman expeditions were done in order to reach it, Septimius Flaccus and Julius Maternus reached the lake of ippopotamus. They moved from coastal Tripolitania and passed near the Tibesti mountains, both did their expeditions through the Garamantes territories, and were able to leave a small garrison on the lake of ippopotamus and rhinoceros after 3 months of travel in desert lands. Lake Chad was first surveyed from shore by Europeans in 1823, in 1851, a party including the German explorer Heinrich Barth carried a boat overland from Tripoli across the Sahara Desert by camel and made the first European waterborne survey. British expedition leader James Richardson died just days before reaching the lake, in Winston Churchill’s book The River War, An Account of the Reconquest of the Sudan, published in 1899, Churchill specifically mentions the shrinking of Lake Chad. He writes, Altogether France has enough to occupy her in Central Africa for some time to come, and even when the task is finished. They include the desert of the Great Sahara and wide expanses of equally profitless scrub or marsh, an increased demand on the lakes water from the local population has likely accelerated its shrinkage over the past 40 years. The size of Lake Chad greatly varies seasonally with the flooding of the wetlands areas, in 1983, Lake Chad was reported to have covered 10,000 to 25,000 km2, had a maximum depth of 11 metres, and a volume of 72 km3. By 2000, its extent had fallen to less than 1,500 km2, a 2001 study published in the Journal of Geophysical Research blamed the lakes retreat largely on overgrazing in the area surrounding the lake, causing desertification and a decline in vegetation. The United Nations Environment Programme and the Lake Chad Basin Commission concur that at least half of the decrease is attributable to shifting climate patterns
10.
Adamawa Plateau
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The Adamawa Plateau is a plateau region in west-central Africa stretching from south-eastern Nigeria through north-central Cameroon to the Central African Republic. The plateau was named after Fulani Muslim leader Modibo Adama, the part of the plateau that lies in Nigeria is more popularly known as Gotel Mountains. The Adamawa Plateau is the source of many waterways, including the Benue River and it is important for its deposits of bauxite. The average elevation is about 3,300 feet, but elevations can reach as high as 8,700 feet, the vegetation is mostly savanna, and is sparsely populated. Cattle raising is the occupation in the area. The endangered toad Amietophrynus djohongensis is only known from the Adamawa Plateau in Cameroon
11.
Jos Plateau
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The Jos Plateau is a plateau located near the centre of Nigeria. It covers 8600 km² and is bounded by 300-600 meter escarpments around much of its circumference, with an average altitude of 1280 metres it is the largest area over 1000 metres in Nigeria, with a high point of 1829 metres in the Shere Hills. The plateau has given its name to the State, Plateau State in which it is found and is named for the states capital. The Jos Plateau is dominated by three rock types, the Older Granites date to the late Cambrian and Orduvician. The Younger Granites are emplacements dating to the Jurassic, and forming part of a series that includes the Aïr Massif in the central Sahara, there are also many volcanoes and sheets of basalt extruded since the Pliocene. The Younger Granites contain tin which was mined since the beginning of the 20th century, during, important rivers are Kaduna, Gongola, Hadejia and Yobe, which have their source in this place. The climate on the Plateau is the climate with temperatures ranging from 18 °C to 25 °C. The Jos Plateau is home to the ancient Nok culture, known for its remarkable terracotta artwork, the Jos Plateau lies in the Nigerian Middle Belt, and even in this region known for cultural diversity, it is unusually diverse. Barbour et al. show over 60 ethno-linguistic groups on the plateau, most of the plateaus languages are in the Chadic family, which is part of the Afro-Asiatic family. Two of the Plateaus largest ethnic groups are the Berom, in the northern Plateau, smaller groups include the Mwaghavul, Pyem, Ron, Afizere, Anaguta, Aten, Irigwe, Chokfem, and Kofyar. There is currently no conservation program for this ecoregion, due to tin mining activity some 320 km² of agricultural land has been disturbed. The situation has improved since by local farmers due to usage of traditional as well as modern fertilisation methods which combined includes manure, urban waste ash. In Studies in the History of Plateau State, Nigeria, ed. by Elizabeth Isichei, archived from the original on 2010-03-08
12.
Niger River
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The Niger River is the principal river of western Africa, extending about 4,180 km. Its drainage basin is 2,117,700 km2 in area and its source is in the Guinea Highlands in southeastern Guinea. The Niger is the third-longest river in Africa, exceeded only by the Nile and its main tributary is the Benue River. The Scottish explorer Mungo Park was the first Westerner known to have travelled to the portion of the Niger River. The earliest use of the name Niger for the river is by Leo Africanus in his Della descrittione dell’Africa et delle cose notabili che iui sono published in Italian in 1550, the name may come from Berber phrase ger-n-ger meaning river of rivers. As Timbuktu was the end of the principal Trans-Saharan trade route to the western Mediterranean. When European colonial powers began to send ships along the West coast of Africa in the 16th and 17th centuries, the Niger Delta, pouring into the Atlantic through mangrove swamps and thousands of distributaries along more than 160 kilometres, was thought to be no more than coastal wetlands. The Niger River is a clear river, carrying only a tenth as much sediment as the Nile because the Nigers headwaters lie in ancient rocks that provide little silt. Like the Nile, the Niger floods yearly, this begins in September, peaks in November, an unusual feature of the river is the Inner Niger Delta, which forms where its gradient suddenly decreases. The result is a region of braided streams, marshes, and lakes the size of Belgium, the river loses nearly two-thirds of its potential flow in the Inner Delta between Ségou and Timbuktu to seepage and evaporation. All the water from the Bani River, which flows into the Delta at Mopti, the average loss is estimated at 31 km3/year, but varies considerably between years. The river is joined by various tributaries, but also loses more water to evaporation. The quantity of water entering Nigeria measured in Yola was estimated at 25 km3/year before the 1980s, the most important tributary of the Niger in Nigeria is the Benue River which merges with the river at Lokoja in Nigeria. The Niger takes one of the most unusual routes of any major river and this strange geography apparently came about because the Niger River is two ancient rivers joined together. Over time upstream erosion by the lower Niger resulted in capture of the upper Niger by the lower Niger. The northern part of the river, known as the Niger bend, is an important area because it is the major river and this made it the focal point of trade across the western Sahara, and the centre of the Sahelian kingdoms of Mali and Gao. The surrounding Niger River Basin is one of the distinct physiographic sections of the Sudan province, the origin of the rivers name remains unclear. What is clear is that Niger was an appellation applied in the Mediterranean world from at least the Classical era, when knowledge of the area by Europeans was slightly better than fable
13.
Benue River
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The Benue River, previously known as the Chadda River or Tchadda, is the major tributary of the Niger River. The river is approximately 1,400 kilometres long and is almost entirely navigable during the summer months, as a result, it is an important transportation route in the regions through which it flows. Large tributaries are the Faro River, the Gongola River and the Mayo Kébbi, other tributaries are Taraba River and River Katsina Ala. At the point of confluence, the Benue exceeds the Niger by volume, the mean discharge before 1960 was 3,400 cubic metres per second for the Benue and 2,500 cubic metres per second for the Niger. During the following decades, the runoff of both rivers decreased markedly due to irrigation, the Benue River flooded in October 2012, resulting in a large increase in the population of venomous snakes in the Duguri District, Alkaleri Local Government Area, Bauchi State. A July 2013 report indicated that over 200 people in the district had died of snakebite. The General Hospital in Kaltungo, Gombe State is the nearest location for treatment of snakebite, whoever is lucky to make it to Kaltungo is treated in only two days and then they return home
14.
Niger Delta
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The Niger Delta is the delta of the Niger River sitting directly on the Gulf of Guinea on the Atlantic Ocean in Nigeria. Of all the states that the covers, only Cross River is not an oil-producing state. Niger Delta is a densely populated region sometimes called the Oil Rivers because it was once a major producer of palm oil. The area was the British Oil Rivers Protectorate from 1885 until 1893, the delta is a petroleum-rich region, and has been the centre of international controversy over pollution, corruption, and human rights violations. The Niger Delta, as now defined officially by the Nigerian government, extends over about 70,000 km2, historically and cartographically, it consists of present-day Bayelsa, Delta, and Rivers States. In 2000, however, Obasanjos regime included Abia, Akwa-Ibom, Cross River State, Edo, Imo, the Niger Delta, and the South South geopolitical zone are two different entities. The Niger Delta separates the Bight of Benin from the Bight of Biafra within the larger Gulf of Guinea, the area was the British Oil Rivers Protectorate from 1885 until 1893, when it was expanded and became the Niger Coast Protectorate. The core Niger Delta later became a part of the region of Nigeria. The majority of the people were those from the colonial Calabar and Ogoja divisions, the present-day Ogoja, Annang, Ibibio, Oron, Efik, the National Council of Nigeria and Cameroon was the ruling political party of the region. The NCNC later became the National Convention of Nigerian Citizens, after western Cameroon decided to separate from Nigeria, the ruling party of eastern Nigeria did not seek to preclude the separation and even encouraged it. The then Eastern Region had the second, fourth and fifth largest ethnic groups in the country the Igbo, the Ijaw and the Ibibio after the Hausa-Fulani and the Yoruba. In 1953, the old eastern region had a crisis due to the expulsion of professor Eyo Ita from office by the majority Igbo tribe of the old eastern region. Ita, an Efik man from Calabar, was one of the nationalists for Nigerian independence. The struggle for the creation of the COR state continued and was an issue concerning the status of minorities in Nigeria during debates in Europe on Nigerian independence. The aftermath of the 1961 plebiscite has led to a dispute between Cameroon and Nigeria over the territory of Bakassi. A new phase of the saw the declaration of an Independent Niger Delta Republic by Isaac Adaka Boro during Nigerian president Ironsis administration. Also just before the Nigerian civil war, Southeastern State of Nigeria was created, which had the colonial Calabar division, and colonial Ogoja division. Southeastern state and River state became two states for the minorities of the old eastern region, and the majority Igbo of the old eastern region had a state called East Central state
15.
Tropics
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The tropics are a region of the Earth surrounding the equator. The tropics are also referred to as the zone and the torrid zone. The tropics include all the areas on the Earth where the Sun is at a point directly overhead at least once during the solar year. The tropics are distinguished from the climatic and biomatic regions of Earth, which are the middle latitudes. Tropical is sometimes used in a sense for a tropical climate to mean warm to hot and moist year-round. Many tropical areas have a dry and wet season, the wet season, rainy season or green season, is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is distributed through the year. When the wet season occurs during the season, or summer, precipitation falls mainly during the late afternoon. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime, unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Regions within the tropics may well not have a tropical climate, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the tropics is classed not as tropical but as dry including the Sahara Desert. Tropical plants and animals are those native to the tropics. Tropical ecosystems may consist of rainforests, dry forests, spiny forests, desert. There are often significant areas of biodiversity, and species present, particularly in rainforests. In biogeography, the tropics are divided into Paleotropics and Neotropics, together, they are sometimes referred to as the Pantropic
16.
Southern Nigeria Protectorate
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The Lagos colony was later added in 1906, and the territory was officially renamed the Colony and Protectorate of Southern Nigeria. In 1914, Southern Nigeria was joined with Northern Nigeria Protectorate to form the colony of Nigeria. Sir Frederick Lugard, who took office as governor of both protectorates in 1912, was responsible for overseeing the unification, and he became the first governor of the united territory. Lugard established several central institutions to anchor the evolving unified structure, a Central Secretariat was instituted at Lagos, which was the seat of government, and the Nigerian Council, was founded to provide a forum for representatives drawn from the provinces. The process of unification was undermined by the persistence of different regional perspectives on governance between the Northern and Southern Provinces, and by Nigerian nationalists in Lagos. Southerners, on their part, were not eager to embrace the extension of legislation originally meant for the north to the south, from its foundation southern Nigeria was administered by a high commissioner. The first high commissioner was Ralph Moor, when Lagos was amalgamated with the rest of southern Nigeria in 1906, the then high commissioner Walter Egerton was made into Governor of the territory. Egerton became Governor of Lagos Colony, covering most of the Yoruba lands in the southwest of what is now Nigeria and he held both offices until 28 February 1906. On that date the two territories were united and Egerton was appointed Governor of the new Colony and Protectorate of Southern Nigeria. When his predecessor in Southern Nigeria, Sir Ralph Denham Rayment Moor, resigned, on taking office, Egerton began a policy of sending out annual pacification patrols, which generally obtained submission through the threat of force without being required to actually use force. When Egerton became Governor of Lagos he enthusiastically endorsed the extension of the Lagos – Ibadan railway onward to Oshogbo, construction began in January 1905 and the line reached Oshogbo in April 1907. He favored rail over river transport, and pushed to have the railway extended to Kano by way of Zaria. He also sponsored extensive road construction, building on the foundation laid by his predecessor Moor which enabled use of unpaid local labor. Egerton shared Moors views on the damage that was being done to the Cross River trade by the combination of indigenous middlemen, Egerton was a strong advocate of colonial development. He believed in deficit financing at certain periods of a colonys growth and he had a constant struggle to obtain approval for these budgets from the colonial office. As early as 1908, Egerton supported the idea of a properly organized Agricultural Department with an energetic and experienced head, and the Department of Agriculture came into being in 1910. Egerton endorsed the development of plantations, a concept familiar to him from his time in Malaya. This was the foundation of a successful industry
17.
Northern Region, Nigeria
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Northern Nigeria was an autonomous division within Nigeria, distinctly different from the southern part of the country, it had independent customs, foreign relations and security structures. In 1962 it acquired the territory of the British Northern Cameroons, the Kwatarkwashi culture, a variant of the Nok culture centred mostly around Zamfara in Sokoto Province is thought by some to be the same or an offshoot of the Nok. The Fourteen Kingdoms unified the diverse lore and heritage of Northern Nigeria into a cohesive ethno-historical system, Seven of these Kingdoms developed from the Kabara legacy of the Hausa people. The Seven Hausa states included, Daura, -1806 Kano 998 -1807 Katsina c.1400 -1805 Zazzau c.1200 -1808 Gobir. Thus they are called the Banza Bakwai meaning Bastard Seven, the Banza Bakwai adopted many of the customs and institutions of the Hausa Bakwai but were considered unsanctioned or copy-cat kingdoms by non-Hausa people. With the decline of the Nok and Sokoto, who had previously controlled Central and they are closely linked with the Kanuri people of Kanem-Bornu, the Birom, Gwari, Nupe and Jukun. The Hausa aristocracy, under influence from the Mali Empire adopted Islam in the 11th century CE, by the 12th century CE the Hausa were becoming one of Africas major powers. The architecture of the Hausa is perhaps one of the least known, many of their early mosques and palaces are bright and colourful and often include intricate engraving or elaborate symbols designed into the facade. By 1500 CE the Hausa utilized a modified Arabic script known as Ajami to record their own language, the Hausa compiled several written histories, usuman dan Fodio led a jihad against the Hausa States and finally united them into the Sokoto Caliphate. The Sokoto Caliphate was under the authority of the Commander of the Faithful. Under Dan Fodio, the Empire was bicephalous and divided into two territories each controlled by an appointed vizier, each of the territories was further divided into autonomous Emirates under mainly hereditary local Emirs. The Bornu Empire was initially absorbed into the Sokoto Caliphate of Usman dan Fodio, the Royal Niger Companys territory did not represent a direct threat to much the Sokoto Caliphate or the numerous states of Northern Nigeria. This changed, when Fredrick Lugard and Taubman Goldie laid down a plan to pacify the Niger interior. The protectorate of Northern Nigeria was proclaimed at Ida by Fredrick Lugard on January 1,1897, the basis of the colony was the 1885 Treaty of Berlin which broadly granted Northern Nigeria to Britain, on the basis of their protectorates in Southern Nigeria. Hostilities with the powerful Sokoto Caliphate soon followed, the Emirates of Kotogora and Illorin were the first to be conquered by the British. In February 1903, the fort of Kano, seat of the Kano Emirate was captured, Sokoto. On March 13,1903, the Grand Shura of Caliphate finally conceded to Lugards demands and proclaimed Queen Victoria, Queen and sovereign of the Caliphate and all its lands. The Governor, Frederick Lugard, with limited resources, ruled with the consent of local rulers through a policy of rule which he developed into a sophisticated political theory
18.
Tropical monsoon climate
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Tropical monsoon climates have monthly mean temperatures above 18 °C in every month of the year and feature wet and dry seasons, as Tropical savanna climates do. Tropical monsoon climates however features its driest month seeing on average less than 60 mm and this latter fact is in direct contrast to a tropical savanna climate, whose driest month sees less than 60 mm of precipitation and also less than 100 – of precipitation. In essence, a monsoon climate tends to either see more rainfall than a tropical savanna climate or have less pronounced dry seasons. Additionally, a monsoon climate tends to see less variance in temperatures during the course of the year than a tropical savanna climate. This climate has a driest month which nearly always occurs at or soon after the winter solstice for that side of the equator, there are generally two versions of a tropical monsoon climate, Less pronounced dry seasons. Regions with this variation of the monsoon climate typically see copious amounts of rain during the wet season. However, unlike most tropical climates, a sizeable amount of precipitation also falls during the dry season. In essence, this version of the monsoon climate generally has less pronounced dry seasons than tropical savanna climates. Extraordinarily rainy wet seasons and pronounced dry seasons and this variation features pronounced dry seasons similar in length and character to dry seasons observed in tropical savanna climates. However, this is followed by a period of extraordinary rainfall. In some instances, up to 1,000 mm of precipitation is observed per month for two or more consecutive months, Tropical savanna climates generally do not see this level of sustained rainfall. Tropical monsoon climates are most commonly found in South and Central America, however, there are sections of South Asia, Southeast Asia, Africa, the Caribbean and North America that also feature this climate. The major controlling factor over a tropical climate is its relationship to the monsoon circulation. The monsoon is a change in wind direction. In Asia, during the summer there is a flow of air. In the “winter” an offshore air flow is prevalent, the change in direction is due to the difference in the way water and land heat. October is the hottest month no matter whether is it in the southern or northern hemisphere and this is because October is the shoulder season of the year as if it is the end of the wet season and no winter winds blowing. Changing pressure patterns that affect the seasonality of precipitation occur in Africa though it generally differs from the way it operates in Asia
19.
Monsoon
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Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is sometimes used for locally heavy but short-term rains. The major monsoon systems of the world consist of the West African and Asia-Australian monsoons, the inclusion of the North and South American monsoons with incomplete wind reversal has been debated. The south-west monsoon winds are called Nairutya Maarut in India, the English monsoon came from Portuguese monção, ultimately from Arabic mawsim and/or Hindi mausam, perhaps partly via early modern Dutch monsun. Strengthening of the Asian monsoon has been linked to the uplift of the Tibetan Plateau after the collision of the Indian sub-continent and Asia around 50 million years ago. Because of studies of records from the Arabian Sea and that of the wind-blown dust in the Loess Plateau of China, testing of this hypothesis awaits deep ocean sampling by the Integrated Ocean Drilling Program. The monsoon has varied significantly in strength since this time, largely linked to climate change. A study of marine plankton suggested that the Indian Monsoon strengthened around 5 million years ago, then, during ice periods, the sea level fell and the Indonesian Seaway closed. When this happened, cold waters in the Pacific were impeded from flowing into the Indian Ocean and it is believed that the resulting increase in sea surface temperatures in the Indian Ocean increased the intensity of monsoons. Five episodes during the Quaternary at 2.22 Ma,1.83 Ma,0.68 Ma,0.45 Ma and 0.04 Ma were identified which showed a weakening of Leeuwin Current. The weakening of the LC would have an effect on the sea surface temperature field in the Indian Ocean, thus these five intervals could probably be those of considerable lowering of SST in the Indian Ocean and would have influenced Indian monsoon intensity. The impact of monsoon on the weather is different from place to place. In some places there is just a likelihood of having a more or less rain. In other places, quasi semi-deserts are turned into green grasslands where all sorts of plants. The Indian Monsoon turns large parts of India from a kind of semi-desert into green lands, see photos only taken 3 months apart in the Western Ghats. In places like this it is crucial for farmers to have the right timing for putting the seeds on the fields, Monsoons are large-scale sea breezes which occur when the temperature on land is significantly warmer or cooler than the temperature of the ocean. These temperature imbalances happen because oceans and land absorb heat in different ways, in contrast, dirt, sand, and rocks have lower heat capacities, and they can only transmit heat into the earth by conduction and not by convection. Therefore, bodies of water stay at an even temperature
20.
Atlantic Ocean
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The Atlantic Ocean is the second largest of the worlds oceans with a total area of about 106,460,000 square kilometres. It covers approximately 20 percent of the Earths surface and about 29 percent of its surface area. It separates the Old World from the New World, the Atlantic Ocean occupies an elongated, S-shaped basin extending longitudinally between Eurasia and Africa to the east, and the Americas to the west. The Equatorial Counter Current subdivides it into the North Atlantic Ocean, in contrast, the term Atlantic originally referred specifically to the Atlas Mountains in Morocco and the sea off the Strait of Gibraltar and the North African coast. The Greek word thalassa has been reused by scientists for the huge Panthalassa ocean that surrounded the supercontinent Pangaea hundreds of years ago. The term Aethiopian Ocean, derived from Ancient Ethiopia, was applied to the Southern Atlantic as late as the mid-19th century, many Irish or British people refer to the United States and Canada as across the pond, and vice versa. The Black Atlantic refers to the role of ocean in shaping black peoples history. Irish migration to the US is meant when the term The Green Atlantic is used, the term Red Atlantic has been used in reference to the Marxian concept of an Atlantic working class, as well as to the Atlantic experience of indigenous Americans. Correspondingly, the extent and number of oceans and seas varies, the Atlantic Ocean is bounded on the west by North and South America. It connects to the Arctic Ocean through the Denmark Strait, Greenland Sea, Norwegian Sea, to the east, the boundaries of the ocean proper are Europe, the Strait of Gibraltar and Africa. In the southeast, the Atlantic merges into the Indian Ocean, the 20° East meridian, running south from Cape Agulhas to Antarctica defines its border. In the 1953 definition it extends south to Antarctica, while in later maps it is bounded at the 60° parallel by the Southern Ocean, the Atlantic has irregular coasts indented by numerous bays, gulfs, and seas. Including these marginal seas the coast line of the Atlantic measures 111,866 km compared to 135,663 km for the Pacific. Including its marginal seas, the Atlantic covers an area of 106,460,000 km2 or 23. 5% of the ocean and has a volume of 310,410,900 km3 or 23. 3%. Excluding its marginal seas, the Atlantic covers 81,760,000 km2 and has a volume of 305,811,900 km3, the North Atlantic covers 41,490,000 km2 and the South Atlantic 40,270,000 km2. The average depth is 3,646 m and the maximum depth, the bathymetry of the Atlantic is dominated by a submarine mountain range called the Mid-Atlantic Ridge. It runs from 87°N or 300 km south of the North Pole to the subantarctic Bouvet Island at 42°S, the MAR divides the Atlantic longitudinally into two halves, in each of which a series of basins are delimited by secondary, transverse ridges. The MAR reaches above 2000 m along most of its length, the MAR is a barrier for bottom water, but at these two transform faults deep water currents can pass from one side to the other
21.
Air mass (astronomy)
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In astronomy, air mass is the optical path length through Earth’s atmosphere for light from a celestial source. As it passes through the atmosphere, light is attenuated by scattering and absorption, the atmosphere through which it passes. Consequently, celestial bodies at the horizon appear less bright than when at the zenith, the attenuation, known as atmospheric extinction, is described quantitatively by the Beer–Lambert–Bouguer law. “Air mass” normally indicates relative air mass, the path length relative to that at the zenith at sea level so, by definition, Air mass increases as the angle between the source and the zenith increases, reaching a value of approximately 38 at the horizon. The region above Earth’s atmosphere, where there is no attenuation of solar radiation, is considered to have “air mass zero”. Tables of air mass have been published by authors, including Bemporad, Allen. The angle of a body with the zenith is the zenith angle. A body’s angular position can also be given in terms of altitude, the angle above the horizon, the altitude h. Atmospheric refraction causes light to follow a circular path that is slightly longer than the geometric path. Most air mass formulas are based on the apparent zenith angle, when the zenith angle is small to moderate, a good approximation is given by assuming a homogeneous plane-parallel atmosphere. The air mass X then is simply the secant of the angle z, X = sec z. At a zenith angle of 60°, the air mass is approximately 2, the Earth is not flat, however, and, depending on accuracy requirements, this formula is usable for zenith angles up to about 60° to 75°. At greater zenith angles, the accuracy degrades rapidly, with X = sec z becoming infinite at the horizon, the horizon air mass in the more-realistic spherical atmosphere is usually less than 40. Many formulas have been developed to fit tabular values of air mass, one by Young and Irvine included a simple corrective term, X = sec z t and this gives usable results up to approximately 80°, but the accuracy degrades rapidly at greater zenith angles. The calculated air mass reaches a maximum of 11.13 at 86. 6°, becomes zero at 88°, the plot of this formula on the accompanying graph includes a correction for atmospheric refraction so that the calculated air mass is for apparent rather than true zenith angle. Hardie introduced a polynomial in sec z −1, X = sec z −0.0018167 −0.0028752 −0.00080833 which gives usable results for zenith angles of up to perhaps 85°. As with the formula, the calculated air mass reaches a maximum. Rozenberg suggested X = −1, which gives reasonable results for zenith angles
22.
Warri
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The city of Warri is an oil hub in South-South Nigeria and houses an annex of the Delta State Government House. It served as the capital of the then Warri Province. It shares boundaries with Ughelli/Agbarho, Sapele, Okpe, Udu and Uvwie although most of places, notably Udu, Okpe. Osubi houses an airport that serves the city, Effurun serves as the gateway to and the economic nerve of the city. Warri has a history that has not been documented well enough by historians. The name Warri province was once applicable to the part of an area now called Delta State under the Colony and Protectorate of Southern Nigeria. Its boundary in the Northeast was Sapele/Udu creek near Ughelli and Aboh, with Forçados River in the Southeast, Warri city is one of the major hubs of petroleum activities and businesses in the southern Nigeria. It is a capital city of Delta State, with a population of over 311,970 people according to the national population census figures for 2006. The city is one of cities in southern Nigeria comprising originally of Urhobo, Itsekiri. Warri is predominantly Christian with mixture of African traditional religions like most of the Southern Nigeria, the city is known nationwide for its unique Pidgin English. Warri was once a capital to British rule. Warri sits on the bank of River Warri which joined River Forcados, the city has a modern seaport which serves as the cargo transit point between the Niger River and the Atlantic Ocean for import and export. The citys history dates back to the 15th century, when it was visited by Portuguese missionaries, subsequently, it served as the base for Portuguese and Dutch slave traders. Warri was then established as a headquarters by the British in the early 20th century. There have been a growth in the population, it has grown from being a rural area to an urban area. Each of these areas has its own administrative structure, Warri City is residence to four monarchs namely the Olu of Warri, Orosuen of the Okere-Warri Kingdom, the Ovie of Agbarha-Warri Kingdom and the Pere of Ogbe Ijaw -Warri Kingdom. The major people in Warri comprise the Urhobos, Ijaws and Itsekiris, however, due to its urban status, there is a large influx of people from all over the country, most notably the Igbos. The region experiences moderate rainfall and moderate humidity for most part of the year, the climate is monsoonal and is marked by two distinct seasons, the dry season and the rainy season
23.
Precipitation
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In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation include drizzle, rain, sleet, snow, graupel, Precipitation occurs when a portion of the atmosphere becomes saturated with water vapor, so that the water condenses and precipitates. Thus, fog and mist are not precipitation but suspensions, because the vapor does not condense sufficiently to precipitate. Two processes, possibly acting together, can lead to air becoming saturated, Precipitation forms as smaller droplets coalesce via collision with other rain drops or ice crystals within a cloud. Short, intense periods of rain in scattered locations are called showers, moisture that is lifted or otherwise forced to rise over a layer of sub-freezing air at the surface may be condensed into clouds and rain. This process is active when freezing rain is occurring. A stationary front is often present near the area of freezing rain, provided necessary and sufficient atmospheric moisture content, the moisture within the rising air will condense into clouds, namely stratus and cumulonimbus. Eventually, the droplets will grow large enough to form raindrops. Lake-effect snowfall can be locally heavy, thundersnow is possible within a cyclones comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation, on the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of the trough, or intertropical convergence zone. Precipitation is a component of the water cycle, and is responsible for depositing the fresh water on the planet. Approximately 505,000 cubic kilometres of water falls as precipitation each year,398,000 cubic kilometres of it over the oceans and 107,000 cubic kilometres over land. Given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres, Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Precipitation may occur on celestial bodies, e. g. when it gets cold, Mars has precipitation which most likely takes the form of frost. Precipitation is a component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km3 of water falls as precipitation each year,398,000 km3 of it over the oceans, given the Earths surface area, that means the globally averaged annual precipitation is 990 millimetres. Mechanisms of producing precipitation include convective, stratiform, and orographic rainfall, Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice
24.
Equator
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The Equator usually refers to an imaginary line on the Earths surface equidistant from the North Pole and South Pole, dividing the Earth into the Northern Hemisphere and Southern Hemisphere. The Equator is about 40,075 kilometres long, some 78. 7% lies across water and 21. 3% over land, other planets and astronomical bodies have equators similarly defined. Generally, an equator is the intersection of the surface of a sphere with the plane that is perpendicular to the spheres axis of rotation. The latitude of the Earths equator is by definition 0° of arc, the equator is the only line of latitude which is also a great circle — that is, one whose plane passes through the center of the globe. The plane of Earths equator when projected outwards to the celestial sphere defines the celestial equator, in the cycle of Earths seasons, the plane of the equator passes through the Sun twice per year, at the March and September equinoxes. To an observer on the Earth, the Sun appears to travel North or South over the equator at these times, light rays from the center of the Sun are perpendicular to the surface of the Earth at the point of solar noon on the Equator. Locations on the Equator experience the quickest sunrises and sunsets because the sun moves nearly perpendicular to the horizon for most of the year. The Earth bulges slightly at the Equator, the diameter of the Earth is 12,750 kilometres. Because the Earth spins to the east, spacecraft must also launch to the east to take advantage of this Earth-boost of speed, seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earths axis relative to the plane of revolution. During the year the northern and southern hemispheres are inclined toward or away from the sun according to Earths position in its orbit, the hemisphere inclined toward the sun receives more sunlight and is in summer, while the other hemisphere receives less sun and is in winter. At the equinoxes, the Earths axis is not tilted toward the sun, instead it is perpendicular to the sun meaning that the day is about 12 hours long, as is the night, across the whole of the Earth. Near the Equator there is distinction between summer, winter, autumn, or spring. The temperatures are usually high year-round—with the exception of high mountains in South America, the temperature at the Equator can plummet during rainstorms. In many tropical regions people identify two seasons, the wet season and the dry season, but many places close to the Equator are on the oceans or rainy throughout the year, the seasons can vary depending on elevation and proximity to an ocean. The Equator lies mostly on the three largest oceans, the Pacific Ocean, the Atlantic Ocean, and the Indian Ocean. The highest point on the Equator is at the elevation of 4,690 metres, at 0°0′0″N 77°59′31″W and this is slightly above the snow line, and is the only place on the Equator where snow lies on the ground. At the Equator the snow line is around 1,000 metres lower than on Mount Everest, the Equator traverses the land of 11 countries, it also passes through two island nations, though without making a landfall in either. Starting at the Prime Meridian and heading eastwards, the Equator passes through, Despite its name, however, its island of Annobón is 155 km south of the Equator, and the rest of the country lies to the north
25.
Tropical savanna climate
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Tropical savanna climate or tropical wet and dry climate is a type of climate that corresponds to the Köppen climate classification categories Aw and As. This latter fact is in direct contrast to a monsoon climate. In essence, a savanna climate tends to either see less rainfall than a tropical monsoon climate or have more pronounced dry seasons. There are generally four types of tropical climate,1. Distinct wet and dry seasons of relatively equal duration, most of the regions annual rainfall is experienced during the wet season and very little precipitation falls during the dry season. A lengthy dry season and a short wet season. This version features seven or more dry season months and five or less wet season months, there are variations within this version, On one extreme, the region receives just enough precipitation during the short wet season to preclude it from a semi-arid climate classification. This drier variation of the savanna climate is typically found adjacent to regions with semi-arid climates. On the other extreme, the features a lengthy dry season followed by a short. However, regions with this variation of the climate do not experience enough rainfall during the wet season to qualify as a monsoon climate. A lengthy wet season and a short dry season. This version features seven or more wet season months and five or less dry season months, a dry season with a noticeable amount of rainfall followed by a rainy wet season. Tropical savanna climates are most commonly found in Africa, Asia, the climate is also prevalent in sections of Central America, northern Australia and southern North America, specifically in sections of Mexico and the state of Florida in the United States. Most places that have this climate are found at the margins of the tropical zone. Similarly, the Caribbean coast, eastward from the Gulf of Urabá on the Colombia – Panamá border to the Orinoco river delta and this condition extends to the Lesser Antilles and Greater Antilles forming the Circumcaribbean dry belt. The length and severity of the dry season diminishes inland, at the latitude of the Amazon river—which flows eastward, East from the Andes, between the arid Caribbean and the ever-wet Amazon are the Orinoco river llanos or savannas, from where this climate takes its name. Sometimes As is used in place of Aw if the dry season occurs during the time of higher sun and this is the case in parts of Hawaii, East Africa, Sri Lanka and coastal regions of Northeastern Brazil, for instance. The difference between summer and winter in such locations is usually so slight that a distinction between an As and Aw climate is a quibble
26.
Abuja
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Abuja is the capital city of Nigeria located in the centre of the country within the Federal Capital Territory. It is a city and was built mainly in the 1980s. Abujas geography is defined by Aso Rock, a 400-metre monolith left by water erosion, the Presidential Complex, National Assembly, Supreme Court and much of the city extend to the south of the rock. Zuma Rock, a 792-metre monolith, lies just north of the city on the road to Kaduna State, at the 2006 census, the city of Abuja had a population of 776,298, making it one of the ten most populous cities in Nigeria. According to the United Nations, Abuja grew by 139. 7% between 2000 and 2010, making it the fastest growing city in the world. The unofficial metropolitan area of Abuja has a population of well over three million, making it the fourth largest metropolitan area in Nigeria, surpassed only by Lagos, Kano, as at 2016, the metropolitan area of Abuja is estimated at 6 million persons. Major religious sites include the Nigerian National Mosque and the Nigerian National Christian Centre, the city is served by the Nnamdi Azikiwe International Airport. Abuja is known for being one of the few capital cities in Africa. The indigenous inhabitants of Abuja are the Gbagyi as the language, Bassa, Gwandara, Gade, Ganagana. The location was designated in the centre of the country in the early 1970s as it signified neutrality. Another impetus for Abuja came because of Lagos population boom that made that city overcrowded, the logic used was similar to the way Brazil planned its capital, Brasília. Construction broke ground and was dedicated in the late 1970s but, due to economic and political instability, the master plan for Abuja defined the general structure and major design elements of the city that are visible in its current form. Most countries relocated their embassies to Abuja, and many maintain their former embassies as consulates in Lagos, Abuja is the headquarters of the Economic Community of West African States and the regional headquarters of OPEC. Abuja and the FCT have experienced population growth, it has been reported that some areas around Abuja have been growing at 20% to 30% per year. Squatter settlements and towns have spread rapidly in and outside the city limits, tens of thousands of people have been evicted since former FCT minister Nasir Ahmad el-Rufai started a demolition campaign in 2003. Along the Airport Road are clusters of settlements, namely Lugbe, Chika, Kuchigworo. Other satellite settlements are Idu, Mpape, Karimu, Gwagwa, Abujas Central District, also called Central Area, spans from the foot of Aso Rock, across the Three Arms Zone, to the southern base of the inner ring road. It is like the citys spinal cord, dividing it into the sector with Maitama and Wuse
27.
Harmattan
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The Harmattan is a season in the West African subcontinent, which occurs between the end of November and the middle of March. It is characterized by dry and dusty trade wind, of the same name. The name comes from or is related to Ga haramata and it is cold in most places, but can be hot in some places, according to the circumstances. On its passage over the Sahara, it picks up fine dust, the Harmattan season differs from winter, because it is characterized by cold, dry, dust-laden wind, and also wide fluctuations in the ambient temperatures of the day and night. Temperatures can easily be as low as 9 °C all day, the air is particularly dry and desiccating when the Harmattan blows over the region. The wind can increase fire risk and cause severe crop damage, the interaction of the Harmattan with monsoon winds can cause tornadoes. In some countries in West Africa, the amount of dust in the air can severely limit visibility and block the sun for several days. This effect is known as the Harmattan haze and it costs airlines millions of dollars in cancelled and diverted flights each year. When the haze is weak, the skies are clear, the dry air can break the trunks of trees growing in the region. Humidity drops to as low as 15%, which can result in spontaneous nosebleeds for some people, other health effects on humans may include conditions of the skin, eyes, and respiratory system, including aggravation of asthma
28.
Sahara
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The Sahara is the largest hot desert and the third largest desert in the world after Antarctica and the Arctic. Its area of 9,200,000 square kilometres is comparable to the area of the United States. The desert comprises much of North Africa, excluding the fertile region on the Mediterranean Sea coast, the Atlas Mountains of the Maghreb, and the Nile Valley in Egypt and Sudan. It stretches from the Red Sea in the east and the Mediterranean in the north to the Atlantic Ocean in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the Sahel, a belt of tropical savanna around the Niger River valley. The Sahara can be divided into several regions including, the western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains, the Ténéré desert, the name Sahara is derived from ṣaḥārā, the plural of the Arabic word for desert. The Sahara covers large parts of Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Western Sahara, Sudan and it covers 9 million square kilometres, amounting to 31% of Africa. If all areas with an annual precipitation of less than 250 mm were included. It is one of three physiographic provinces of the African massive physiographic division. The Sahara is mainly rocky hamada, Ergs form only a minor part, wind or rare rainfall shape the desert features, sand dunes, dune fields, sand seas, stone plateaus, gravel plains, dry valleys, dry lakes, and salt flats. Unusual landforms include the Richat Structure in Mauritania, several deeply dissected mountains, many volcanic, rise from the desert, including the Aïr Mountains, Ahaggar Mountains, Saharan Atlas, Tibesti Mountains, Adrar des Iforas, and the Red Sea hills. The highest peak in the Sahara is Emi Koussi, a volcano in the Tibesti range of northern Chad. The central Sahara is hyperarid, with sparse vegetation, the northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in wadis, where moisture collects. In the central, hyperarid region, there are subdivisions of the great desert, Tanezrouft, the Ténéré, the Libyan Desert, the Eastern Desert. These extremely arid areas often receive no rain for years, the northern limit also corresponds to the 100 mm isohyet of annual precipitation. To the south, the Sahara is bounded by the Sahel, the southern limit of the Sahara is indicated botanically by the southern limit of Cornulaca monacantha, or northern limit of Cenchrus biflorus, a grass typical of the Sahel. According to climatic criteria, the limit of the Sahara corresponds to the 150 mm isohyet of annual precipitation. The Sahara is the worlds largest low-latitude hot desert and this steady descending airflow causes a warming and a drying effect in the upper troposphere
29.
Intertropical Convergence Zone
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The Intertropical Convergence Zone, known by sailors as the doldrums, is the area encircling the earth near the equator where the northeast and southeast trade winds converge. When it lies near the equator, it is called the near-equatorial trough, where the ITCZ is drawn into and merges with a monsoonal circulation, it is sometimes referred to as a monsoon trough, a usage more common in Australia and parts of Asia. In the seamens speech the zone is referred to as the doldrums because of its weather patterns with stagnant calms. The ITCZ appears as a band of clouds, usually thunderstorms, in the Northern Hemisphere, the trade winds move in a southwestern 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, 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 heating, which effectively draw air in. The ITCZ is effectively a tracer of the branch of the Hadley cell. The dry descending branch is the horse latitudes, the location of the intertropical convergence zone varies over time with the seasons. Over land, it moves back and forth across the following the suns zenith point. Over the oceans, where the convergence zone is better defined, 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 ridge of high pressure forms between the two convergence zones. The South Pacific convergence zone is a reverse-oriented, or west-northwest to east-southeast aligned and it lies just south of 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, 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 the equator, 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. Within the ITCZ the average winds are slight, unlike the north and south of the equator where the trade winds feed. Early sailors named this belt of calm the doldrums because of the inactivity, to find oneself becalmed in this region in a hot and muggy climate could mean death in an era when wind was the only effective way to propel ships across the ocean. 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. Tropical cyclogenesis depends upon low-level vorticity as one of its six requirements, surges of higher pressure from high latitudes can enhance tropical disturbances along its axis
30.
Southern Hemisphere
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The Southern Hemisphere is the half sphere of Earth which is south of the equator. It contains all or parts of five continents, four oceans and its surface is 80. 9% water, compared with 60. 7% water in the case of the Northern Hemisphere, and it contains 32. 7% of Earths land. Due to the tilt of Earths rotation relative to the Sun, September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox. The South Pole is in the middle of the southern hemispherical region, Southern Hemisphere climates tend to be slightly milder than those at similar latitudes in the Northern Hemisphere, except in the Antarctic which is colder than the Arctic. This is because the Southern Hemisphere has significantly more ocean and much land, water heats up. In the Southern Hemisphere the sun passes from east to west through the north, sun-cast shadows turn anticlockwise throughout the day and sundials have the hours increasing in the anticlockwise direction. Cyclones and tropical storms spin clockwise in the Southern Hemisphere due to the Coriolis effect, the southern temperate zone, a subsection of the Southern Hemisphere, is nearly all oceanic. Forests in the Southern Hemisphere have special features which set apart from those in the Northern Hemisphere. Both Chile and Australia share, for example, unique species or Nothofagus. The eucalyptus is native to Australia but is now planted in Southern Africa and Latin America for pulp production and, increasingly. Approximately 800,000,000 humans live in the Southern Hemisphere and this is due to the fact that there is significantly less land in the Southern Hemisphere than in the Northern Hemisphere. Africa Antarctica Asia Australia South America Zealandia Media related to Southern Hemisphere at Wikimedia Commons
31.
Squall line
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A squall line is a line of thunderstorms that can form along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front and it contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts. Strong straight-line winds can occur where the line is in the shape of a bow echo. Tornadoes can occur along waves within a line echo wave pattern, some bow echoes which develop within the summer season are known as derechos, and they move quite fast through large sections of territory. On the back edge of the rain associated with mature squall lines. Polar front theory was developed by Jacob Bjerknes, derived from a network of observation sites in Scandinavia during World War I. This theory proposed that the inflow into a cyclone was concentrated along two lines of convergence, one ahead of the low and another trailing behind the low. The trailing convergence zone was referred to as the line or cold front. Areas of clouds and rainfall appeared to be focused along this convergence zone, the concept of frontal zones led to the concept of air masses. The nature of the structure of the cyclone was conceptualized after the development of the upper air network during the 1940s. Organized areas of thunderstorms activity reinforce pre-existing frontal zones, and they can outrun cold fronts and this outrunning occurs within the westerlies in a pattern where the upper level jet splits into two streams. The resultant mesoscale convective system forms at the point of the upper level split in the pattern in the area of best low level inflow. The convection then moves east and toward the equator into the warm sector, when the convection is strong linear or curved, the MCS is called a squall line, with the feature placed at the leading edge of the significant wind shift and pressure rise. This feature is commonly depicted in the season across the United States on surface analyses. If squall lines form over arid regions, a known as a haboob may result from the high winds in their wake picking up dust from the desert floor. Smaller cumulus or stratocumulus clouds, along with cirrus, and, sometimes, altocumulus or cirrocumulus and these clouds are the result of former cumulonimbus clouds having disintegrated, or an area of only minor instability ahead of the main squall line. The areas of dissipating squall line thunderstorms may be regions of low CAPE, low humidity, insufficient wind shear, from here, a general thinning of a squall line will occur, with winds decaying over time, outflow boundaries weakening updrafts substantially and clouds losing their thickness. Because of the nature of updrafts and downdrafts, pressure perturbations are important
32.
Sahel
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The Sahel is the ecoclimatic and biogeographic zone of transition in Africa between the Sahara to the north and the Sudanian Savanna to the south. Having a semi-arid climate, it stretches across the south-central latitudes of Northern Africa between the Atlantic Ocean and the Red Sea, the Arabic word sāḥil literally means shore, coast, while the word Sahara is derived from the Arabic word for desert. Together, these names evoke an image of the Sahels vegetation as a coastline on the Saharas ocean of sand, historically, the western part of the Sahel was sometimes known as the Sudan region. This belt was roughly located between the Sahara and the areas of West Africa. It is an ecoregion of semi-arid grasslands, savannas, steppes. The topography of the Sahel is mainly flat, most of the region lies between 200 and 400 meters in elevation, several isolated plateaus and mountain ranges rise from the Sahel, but are designated as separate ecoregions because their flora and fauna are distinct from the surrounding lowlands. Annual rainfall varies from around 100–200 mm in the north of the Sahel to around 600 mm in the south, the Sahel is mostly covered in grassland and savanna, with areas of woodland and shrubland. Grass cover is continuous across the region, dominated by annual grass species such as Cenchrus biflorus, Schoenefeldia gracilis. Species of acacia are the dominant trees, with Acacia tortilis the most common, along with Acacia senegal, other tree species include Commiphora africana, Balanites aegyptiaca, Faidherbia albida, and Boscia senegalensis. In the northern part of the Sahel, areas of shrub, including Panicum turgidum and Aristida sieberana, alternate with areas of grassland. During the long dry season, many lose their leaves. The larger species have greatly reduced in number by over-hunting and competition with livestock. The seasonal wetlands of the Sahel are important for birds moving within Africa. The Sahel has a tropical, hot steppe climate, the climate is typically hot, sunny, dry and somewhat windy all year long. The Sahels climate is similar to, but less extreme than, the Sahel mainly receives a low to a very low amount of precipitation annually. The steppe has a long, prevailing dry season and a short rainy season. The precipitation is extremely irregular, and varies considerably from season to season. Most of the rain falls during only one or two months, while the other months may remain absolutely dry
33.
Alpine climate
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Alpine climate is the average weather for the regions above the tree line. This climate is referred to as a mountain climate or highland climate. There are multiple definitions of alpine climate, one simple definition is the climate which causes trees to fail to grow due to cold. According to the Holdridge life zone system, alpine climate occurs when the mean biotemperature of a location is between 1.5 and 3 °C, which prevents tree growth. Biotemperature is defined as the temperature, except all temperatures below 0 °C are treated as 0 °C, in the Köppen climate classification, the alpine climate is part of Group E, along with the polar climate, where no month has a mean temperature higher than 10 °C. The temperature profile of the atmosphere is a result of an interaction between radiation and convection, sunlight in the visible spectrum hits the ground and heats it. The ground then heats the air at the surface, however, when air is hot, it tends to expand, which lowers its density. Thus, hot air tends to rise and transfer heat upward and this is the process of convection. Convection comes to equilibrium when a parcel at air at a given altitude has the density as its surroundings. Air is a conductor of heat, so a parcel of air will rise. This is known as a process, which has a characteristic pressure-temperature curve. As the pressure gets lower, the temperature decreases, the rate of decrease of temperature with elevation is known as the adiabatic lapse rate, which is approximately 9.8 °C per kilometre of altitude. Note that the presence of water in the atmosphere complicates the process of convection, water vapor contains latent heat of vaporization. As air rises and cools, it becomes saturated and cannot hold its quantity of water vapor. The water vapor condenses, and releases heat, which changes the rate from the dry adiabatic lapse rate to the moist adiabatic lapse rate. The actual lapse rate, called the lapse rate, is not constant. Therefore, moving up 100 metres on a mountain is roughly equivalent to moving 80 kilometres towards the pole and this relationship is only approximate, however, since local factors, such as proximity to oceans, can drastically modify the climate. As the altitude increases, the form of precipitation becomes snow
34.
Plateau
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Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, and erosion by water and glaciers. Magma rises from the mantle, causing the ground to swell upward, in way, large, flat areas of rock are uplifted. Plateaus can also be built up by lava spreading outward from cracks, plateaus can also be formed by the erosional processes of glaciers on mountain ranges, leaving them sitting between the mountain ranges. Water can also erode mountains and other landforms down into plateaus, volcanic plateaus are produced by volcanic activity. The Columbia Plateau in the northwestern United States is an example, dissected plateaus are highly eroded plateaus cut by rivers and broken by deep narrow valleys. Plateaus are classified according to their surrounding environment, intermontane plateaus are the highest in the world, bordered by mountains. The Tibetan Plateau is one such plateau, Piedmont plateaus are bordered on one side by mountains and on the other by a plain or a sea. The Piedmont Plateau of the Eastern United States between the Appalachian Mountains and the Atlantic Coastal Plain is an example, continental plateaus are bordered on all sides by plains or oceans, forming away from the mountains. The Tibetan plateau covers approximately 2,500,000 km2, the plateau is sufficiently high enough to reverse the Hadley cell convection cycles and to drive the monsoons of India towards the south. The second-highest plateau is the Deosai Plateau of the Deosai National Park at an elevation of 4,114 m. It is located in the Astore and Skardu districts of Gilgit-Baltistan, Deosai means the land of giants. The park protects an area of 3,000 km2 and it is known for its rich flora and fauna of the Karakoram-West Tibetan Plateau alpine steppe ecoregion. In spring it is covered by sweeps of wildflowers and a variety of butterflies. The highest point in Deosai is Deosai Lake, or Sheosar Lake from the Shina language meaning Blind lake near the Chilim Valley. The lake lies at an elevation of 4,142 m, one of the highest lakes in the world, and is 2.3 km long,1.8 km wide, and 40 m deep on average. Some other major plateaus in Asia are, Armenian Highlands, Iranian plateau, Anatolian Plateau, Mongolian Plateau, and the Deccan Plateau. This polar ice cap is so massive that the echolocation sound measurements of ice thickness have shown that parts of the Antarctic dry land surface have been pressed below sea level. Thus, if that same ice cap were removed, the large areas of the frozen white continent would be flooded by the surrounding Antarctic Ocean or Southern Ocean
35.
Season
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A season is a division of the year marked by changes in weather, ecology and hours of daylight. Seasons result from the orbit of the Earth around the Sun. During May, June, and July, the northern hemisphere is exposed to direct sunlight because the hemisphere faces the sun. The same is true of the hemisphere in November, December. It is the tilt of the Earth that causes the Sun to be higher in the sky during the months which increases the solar flux. However, due to lag, June, July, and August are the hottest months in the northern hemisphere and December, January. In temperate and subpolar regions, four calendar-based seasons are recognized, spring, summer, autumn or fall. Ecologists often use a model for temperate climate regions, prevernal, vernal, estival, serotinal, autumnal. Many tropical regions have two seasons, the rainy, wet, or monsoon season and the dry season, some have a third cool, mild, or harmattan season. Seasons often held special significance for agrarian societies, whose lives revolved around planting and harvest times, in some parts of the world, some other seasons capture the timing of important ecological events such as hurricane season, tornado season, and wildfire season. The most historically important of these are the three seasons—flood, growth, and low water—which were previously defined by the annual flooding of the Nile in Egypt. The seasons result from the Earths axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.5 degrees, regardless of the time of year, the northern and southern hemispheres always experience opposite seasons. This is because during summer or winter, one part of the planet is directly exposed to the rays of the Sun than the other. For approximately half of the year, the northern hemisphere tips toward the Sun, for the other half of the year, the same happens, but in the southern hemisphere instead of the northern, with the maximum around December 21. The two instants when the Sun is directly overhead at the Equator are the equinoxes. Also at that moment, both the North Pole and the South Pole of the Earth are just on the terminator, and hence day and night are equally divided between the northern and southern hemispheres. Around the March equinox, the northern hemisphere will be experiencing spring as the hours of daylight increase, the effect of axial tilt is observable as the change in day length and altitude of the Sun at noon during a year. Between this effect and the daylight hours, the axial tilt of the Earth accounts for most of the seasonal variation in climate in both hemispheres
36.
Trade winds
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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, the weaker the trade winds become, the more rainfall can be expected in the neighboring landmasses. The term trade winds originally derives from the fourteenth century late Middle English word trade. The Portuguese recognized the importance of the winds 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 Portugal and they could then turn northeast, to the area around the Azores islands, and finally east to mainland Europe. They also learned that to reach South Africa, they needed to go far out in the ocean, head for Brazil, following the African coast southbound means upwind in the Southern hemisphere. In the Pacific ocean, the wind circulation, which included both the trade wind easterlies and higher-latitude Westerlies, was unknown to Europeans until Andres de Urdanetas voyage in 1565. The captain of a sailing ship seeks a course along which the winds can be expected to blow in the direction of travel, for example, Manila galleons could not sail into the wind at all. Between 1847 and 1849, Matthew Fontaine Maury collected enough information to create wind, as part of the Hadley cell circulation, surface air flows toward the equator while the flow aloft is towards the poles. A low-pressure area of calm, light winds near the equator is known as the doldrums, near-equatorial trough, intertropical front. When located within a region, this zone of low pressure. Around 30° in both hemispheres, air begins to descend toward the surface in subtropical high-pressure belts known as subtropical ridges. The subsident air is dry because as it descends, the temperature increases, but the absolute humidity remains constant. This warm, dry air is known as an air mass. An increase of temperature with height is known as a temperature inversion, when it occurs within a trade wind regime, it is known as a trade wind inversion. The surface air flows from these subtropical high-pressure belts toward the Equator is deflected toward the west in both hemispheres by the Coriolis effect. These winds blow predominantly from the northeast in the Northern Hemisphere, the trade winds of both hemispheres meet at the doldrums. As they blow across tropical regions, air masses heat up over lower latitudes due to direct sunlight
37.
Tropic of Capricorn
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The Tropic of Capricorn is the circle of latitude that contains the subsolar point on the December solstice. It is thus the southernmost latitude where the Sun can be directly overhead and its northern equivalent is the Tropic of Cancer. The Tropic of Capricorn is one of the five major circles of latitude that mark maps of the Earth. As of 3 April 2017, its latitude is 23°26′13. 4″ south of the equator, the Tropic of Capricorn is the dividing line between the Southern Temperate Zone to the south and the tropics to the north. The northern hemisphere equivalent of the Tropic of Capricorn is the Tropic of Cancer, the position of the Tropic of Capricorn is not fixed, but rather it varies in a complex manner over time, see under circles of latitude for information. In southern Africa, where rainfall is more reliable, farming is possible, vegetation here is almost non-existent, though on the eastern slopes of the Andes rainfall is adequate for rainfed agriculture. In modern times the sun appears in the constellation Sagittarius during this time, the change is due to precession of the equinoxes. The word tropic itself comes from the Greek trope, meaning turn, change in direction or circumstances, referring to the fact that the sun appears to turn back at the solstices
38.
Northern Hemisphere
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The Northern Hemisphere is the half of Earth that is north of the equator. For other planets in the Solar System, north is defined as being in the celestial hemisphere relative to the invariable plane of the solar system as Earths North pole. Due to the Earths axial tilt, winter in the Northern Hemisphere lasts from the December solstice to the March Equinox, the dates vary each year due to the difference between the calendar year and the astronomical year. Its surface is 60. 7% water, compared with 80. 9% water in the case of the Southern Hemisphere, the Arctic is the region north of the Arctic Circle. Its climate is characterized by cold winters and cool summers, precipitation mostly comes in the form of snow. The Arctic experiences some days in summer when the Sun never sets, the duration of these phases varies from one day for locations right on the Arctic Circle to several months near the North Pole, which is the middle of the Northern Hemisphere. Between the Arctic Circle and the Tropic of Cancer lies the Northern Temperate Zone, the changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather, tropical regions are generally hot all year round and tend to experience a rainy season during the summer months, and a dry season during the winter months. In the Northern Hemisphere, objects moving across or above the surface of the Earth tend to turn to the right because of the coriolis effect, as a result, large-scale horizontal flows of air or water tend to form clockwise-turning gyres. These are best seen in circulation patterns in the North Atlantic. For the same reason, flows of air down toward the surface of the Earth tend to spread across the surface in a clockwise pattern. Thus, clockwise air circulation is characteristic of high pressure weather cells in the Northern Hemisphere, conversely, air rising from the northern surface of the Earth tends to draw air toward it in a counterclockwise pattern. Hurricanes and tropical storms spin counter-clockwise in the Northern Hemisphere, the shadow of a sundial moves clockwise in the Northern Hemisphere. When viewed from the Northern Hemisphere, the Moon appears inverted compared to a view from the Southern Hemisphere, the North Pole faces away from the galactic center of the Milky Way. The Northern Hemisphere is home to approximately 6.57 billion people which is around 90% of the total human population of 7.3 billion people
39.
Solar irradiance
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Solar irradiance is the power per unit area received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Irradiance may be measured in space or at the Earths surface after atmospheric absorption and it is measured perpendicular to the incoming sunlight. Total solar irradiance, is a measure of the power over all wavelengths per unit area incident on the Earths upper atmosphere. The solar constant is a measure of mean TSI at a distance of one astronomical Unit. Irradiance is a function of distance from the Sun, the solar cycle, Irradiance on Earth is also measured perpendicular to the incoming sunlight. Insolation is the received on Earth per unit area on a horizontal surface. It depends on the height of the Sun above the horizon, the solar irradiance integrated over time is called solar irradiation, solar exposure or insolation. However, insolation is often used interchangeably with irradiance in practice, the SI unit of irradiance is watt per square meter. An alternate unit of measure is the Langley per unit time, the solar energy industry uses watt-hour per square metre per unit time, the relation to the SI unit is thus 1 kW/m2 =24 kWh/m2/day =8760 kWh/m2/year. Irradiance can also be expressed in Suns, where one Sun equals 1000 W/m2 at the point of arrival, part of the radiation reaching an object is absorbed and the remainder reflected. Usually the absorbed radiation is converted to energy, increasing the objects temperature. Manmade or natural systems, however, can convert part of the radiation into another form such as electricity or chemical bonds. The proportion of reflected radiation is the objects reflectivity or albedo, insolation onto a surface is largest when the surface directly faces the sun. As the angle between the surface and the Sun moves from normal, the insolation is reduced in proportion to the angles cosine, see effect of sun angle on climate. In the figure, the angle shown is between the ground and the rather than between the vertical direction and the sunbeam, hence the sine rather than the cosine is appropriate. A sunbeam one mile wide arrives from directly overhead, and another at a 30° angle to the horizontal, the sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area, consequently, half as much light falls on each square mile. This projection effect is the reason why Earths polar regions are much colder than equatorial regions
40.
Atmosphere
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An atmosphere is a layer of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is likely to be retained if the gravity it is subject to is high. The atmosphere of Earth is mostly composed of nitrogen, oxygen, argon with carbon dioxide, the atmosphere helps protect living organisms from genetic damage by solar ultraviolet radiation, solar wind and cosmic rays. Its current composition is the product of billions of years of modification of the paleoatmosphere by living organisms. The term stellar atmosphere describes the region of a star. Stars with sufficiently low temperatures may form compound molecules in their outer atmosphere, Atmospheric pressure is the force per unit area that is applied perpendicularly to a surface by the surrounding gas. It is determined by a gravitational force in combination with the total mass of a column of gas above a location. On Earth, units of air pressure are based on the recognized standard atmosphere. It is measured with a barometer, the pressure of an atmospheric gas decreases with altitude due to the diminishing mass of gas above. The height at which the pressure from an atmosphere declines by a factor of e is called the height and is denoted by H. For such an atmosphere, the pressure declines exponentially with increasing altitude. However, atmospheres are not uniform in temperature, so the determination of the atmospheric pressure at any particular altitude is more complex. Surface gravity, the force that holds down an atmosphere, differs significantly among the planets, for example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from objects with lower gravity. Thus, the distant and cold Titan, Triton, and Pluto are able to retain their atmospheres despite their relatively low gravities, rogue planets, theoretically, may also retain thick atmospheres. Since a collection of gas molecules may be moving at a range of velocities. Lighter molecules move faster than ones with the same thermal kinetic energy. It is thought that Venus and Mars may have lost much of their water when, after being photo dissociated into hydrogen and oxygen by solar ultraviolet, Earths magnetic field helps to prevent this, as, normally, the solar wind would greatly enhance the escape of hydrogen. However, over the past 3 billion years Earth may have lost gases through the polar regions due to auroral activity
41.
Humidity
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Humidity is the amount of water vapor present in the air. Water vapor is the state of water and is invisible. Humidity indicates the likelihood of precipitation, dew, or fog, higher humidity reduces the effectiveness of sweating in cooling the body by reducing the rate of evaporation of moisture from the skin. This effect is calculated in an index table or humidex. The amount of vapor that is needed to achieve saturation increases as the temperature increases. As the temperature of a parcel of water becomes lower it will not reach the point of saturation without adding or losing water mass. The differences in the amount of vapor in a parcel of air can be quite large. For example, a parcel of air that is near saturation may contain 28 grams of water per cubic meter of air at 30 °C, there are three main measurements of humidity, absolute, relative and specific. Absolute humidity is the content of air expressed in gram per cubic meter. Relative humidity, expressed as a percent, measures the current absolute humidity relative to the maximum for that temperature, specific humidity is the ratio of the mass of water vapor to the total mass of the moist air parcel. Absolute humidity is the mass of water vapor present in a given volume of air. It does not take temperature into consideration, absolute humidity in the atmosphere ranges from near zero to roughly 30 grams per cubic meter when the air is saturated at 30 °C. Absolute humidity is the mass of the vapor, divided by the volume of the air and water vapor mixture. The absolute humidity changes as air temperature or pressure changes and this makes it unsuitable for chemical engineering calculations, e. g. for clothes dryers, where temperature can vary considerably. Mass of water per unit volume as in the equation above is defined as volumetric humidity. Because of the confusion, British Standard BS1339 suggests avoiding the term absolute humidity. Units should always be carefully checked, many humidity charts are given in g/kg or kg/kg, but any mass units may be used. The field concerned with the study of physical and thermodynamic properties of mixtures is named psychrometrics
42.
Cumulonimbus cloud
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If observed during a storm, these clouds may be referred to as thunderheads. Cumulonimbus can form alone, in clusters, or along cold front squall lines and these clouds are capable of producing lightning and other dangerous severe weather, such as tornadoes. Cumulonimbus progress from overdeveloped cumulus congestus clouds and may develop as part of a supercell. Cumulonimbus is abbreviated Cb and are designated in the D2 family, towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. The cumulonimbus base may extend several miles across and occupy low to middle altitudes- formed at altitude from approximately 200 to 4,000 m, peaks typically reach to as much as 40,000 ft, with extreme instances as high as 70,000 ft or more. Well-developed cumulonimbus clouds are characterized by a flat, anvil-like top, the shelf of the anvil may precede the main clouds vertical component for many miles, and be accompanied by lightning. Occasionally, rising air parcels surpass the level and form an overshooting top culminating at the maximum parcel level. When vertically developed, this largest of all clouds usually extends through all three cloud regions, even the smallest cumulonimbus cloud dwarfs its neighbors in comparison. Cumulonimbus calvus, cloud with puffy top, similar to cumulus congestus which it develops from, cumulonimbus capillatus, cloud with cirrus-like, fibrous-edged top. Cumulonimbus incus, cloud with anvil top Arcus, low, horizontal cloud formation associated with the edge of thunderstorm outflow. Pannus, accompanied by a layer of fractus species cloud forming in precipitation. Pileus, small cap-like cloud over parent cumulonimbus, velum, a thin horizontal sheet that forms around the middle of a cumulonimbus. Incus, cumulonimbus with flat anvil-like cirriform top caused by wind shear where the air currents hit the inversion layer at the tropopause. Mamma or mammatus, consisting of bubble-like protrusions on the underside, tuba, column hanging from the cloud base which can develop into a funnel cloud or tornado. They are known to very low, sometimes just 20 feet above ground level. Flanking line is a line of small cumulonimbus or cumulus generally associated with severe thunderstorms, rain, precipitation that reaches the ground as liquid, often in a precipitation shaft. Virga, precipitation that evaporates before reaching the ground, cumulonimbus storm cells can produce torrential rain of a convective nature and flash flooding, as well as straight-line winds. Most storm cells die after about 20 minutes, when the precipitation causes more downdraft than updraft, causing the energy to dissipate
43.
Thunderstorm
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Thunderstorms occur in association with a type of cloud known as a cumulonimbus. They are usually accompanied by winds, heavy rain, and sometimes snow, sleet, hail, or, in contrast. Thunderstorms may line up in a series or become a rainband, strong or severe thunderstorms, known as supercells, rotate as do cyclones. Thunderstorms result from the upward movement of warm, moist air. As the warm, moist air moves upward, it cools, condenses, as the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earths surface, as the droplets fall, they collide with other droplets and become larger. Thunderstorms can form and develop in any location but most frequently within the mid-latitude. Thunderstorms are responsible for the development and formation of many weather phenomena. Thunderstorms, and the phenomena that occur along them, pose great hazards. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, stronger thunderstorm cells are capable of producing tornadoes and waterspouts. There are four types of thunderstorms, single-cell, multi-cell cluster, multi-cell lines, supercell thunderstorms are the strongest and the most associated with severe weather phenomena. Mesoscale convective systems formed by vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the lightning that accompanies them. Several means are used to study thunderstorms, weather radar, weather stations, past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earths atmosphere, thunderstorms have also observed on the planets of Jupiter, Saturn, Neptune. Warm air has a lower density than air, so warmer air rises upwards. Clouds form as relatively warmer air, carrying moisture, rises within cooler air, the moist air rises, and, as it does so, it cools and some of the water vapor in that rising air condenses. If enough instability is present in the atmosphere, this process will continue long enough for cumulonimbus clouds to form and produce lightning, Meteorological indices such as convective available potential energy and the lifted index can be used to assist in determining potential upward vertical development of clouds
44.
Latitude
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In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earths surface. Latitude is an angle which ranges from 0° at the Equator to 90° at the poles, lines of constant latitude, or parallels, run east–west as circles parallel to the equator. Latitude is used together with longitude to specify the location of features on the surface of the Earth. Without qualification the term latitude should be taken to be the latitude as defined in the following sections. Also defined are six auxiliary latitudes which are used in special applications, there is a separate article on the History of latitude measurements. Two levels of abstraction are employed in the definition of latitude and longitude, in the first step the physical surface is modelled by the geoid, a surface which approximates the mean sea level over the oceans and its continuation under the land masses. The second step is to approximate the geoid by a mathematically simpler reference surface, the simplest choice for the reference surface is a sphere, but the geoid is more accurately modelled by an ellipsoid. The definitions of latitude and longitude on such surfaces are detailed in the following sections. Lines of constant latitude and longitude together constitute a graticule on the reference surface, latitude and longitude together with some specification of height constitute a geographic coordinate system as defined in the specification of the ISO19111 standard. This is of importance in accurate applications, such as a Global Positioning System, but in common usage, where high accuracy is not required. In English texts the latitude angle, defined below, is denoted by the Greek lower-case letter phi. It is measured in degrees, minutes and seconds or decimal degrees, the precise measurement of latitude requires an understanding of the gravitational field of the Earth, either to set up theodolites or to determine GPS satellite orbits. The study of the figure of the Earth together with its field is the science of geodesy. These topics are not discussed in this article and this article relates to coordinate systems for the Earth, it may be extended to cover the Moon, planets and other celestial objects by a simple change of nomenclature. The primary reference points are the poles where the axis of rotation of the Earth intersects the reference surface, the plane through the centre of the Earth and perpendicular to the rotation axis intersects the surface at a great circle called the Equator. Planes parallel to the plane intersect the surface in circles of constant latitude. The Equator has a latitude of 0°, the North Pole has a latitude of 90° North, the latitude of an arbitrary point is the angle between the equatorial plane and the radius to that point. The latitude, as defined in this way for the sphere, is termed the spherical latitude
45.
North Africa
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North Africa or Northern Africa is the northernmost region of Africa. The United Nationss definition of Northern Africa is, Algeria, Egypt, Libya, Morocco, Sudan, Tunisia, the countries of Algeria, Morocco, Tunisia, and Libya are often collectively referred to as the Maghreb, which is the Arabic word for sunset. Egypt lies to the northeast and encompasses part of West Asia, while Sudan is situated on the edge of the Sahel, Egypt is a transcontinental country because of the Sinai Peninsula, which geographically lies in Western Asia. North Africa also includes a number of Spanish possessions, the Canary Islands and Madeira in the North Atlantic Ocean northwest of the African mainland are included in considerations of the region. From 3500 BC, following the abrupt desertification of the Sahara due to changes in the Earths orbit. The Islamic influence in the area is significant, and North Africa is a major part of the Muslim world. Some researchers have postulated that North Africa rather than East Africa served as the point for the modern humans who first trekked out of the continent in the Out of Africa migration. The Atlas Mountains extend across much of Morocco, northern Algeria and Tunisia, are part of the mountain system that also runs through much of Southern Europe. They recede to the south and east, becoming a steppe landscape before meeting the Sahara desert, the sediments of the Sahara overlie an ancient plateau of crystalline rock, some of which is more than four billion years old. Sheltered valleys in the Atlas Mountains, the Nile Valley and Delta, a wide variety of valuable crops including cereals, rice and cotton, and woods such as cedar and cork, are grown. Typical Mediterranean crops, such as olives, figs, dates and citrus fruits, the Nile Valley is particularly fertile, and most of the population in Egypt and Sudan live close to the river. Elsewhere, irrigation is essential to improve yields on the desert margins. The inhabitants of Saharan Africa are generally divided in a manner corresponding to the principal geographic regions of North Africa, the Maghreb, the Nile valley. The edge of the Sahel, to the south of Egypt has mainly been inhabited by Nubians, Ancient Egyptians record extensive contact in their Western desert with people that appear to have been Berber or proto-Berber, as well as Nubians from the south. They have contributed to the Arabized Berber populations, the official language or one of the official languages in all of the countries in North Africa is Arabic. The people of the Maghreb and the Sahara regions speak Berber languages and several varieties of Arabic, the Arabic and Berber languages are distantly related, both being members of the Afroasiatic language family. The Tuareg Berber languages are more conservative than those of the coastal cities. Over the years, Berbers have been influenced by contact with cultures, Greeks, Phoenicians, Egyptians, Romans, Vandals, Arabs, Europeans
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