Geography of Nigeria

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Satellite image of Nigeria

Nigeria is a country in West Africa. Nigeria shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in the north. Its coast lies on the Gulf of Guinea in the south and it borders Lake Chad to the northeast. Noted geographical features in Nigeria include the Adamawa highlands, Mambilla Plateau, Jos Plateau, Obudu Plateau, the Niger River, River Benue and Niger Delta.

Nigeria is found in the Tropics, where the climate is seasonally damp and very humid. Nigeria is affected by four climate types; these climate types are distinguishable, as one moves from the southern part of Nigeria to the northern part of Nigeria through Nigeria's middle belt.

Climate types found in Nigeria[edit]

The Tropical rainforest climate or the Equatorial monsoon, designated by the Köppen climate classification as "Af", is found in the southern part of the country. This climate is influenced by the monsoons originating from the South Atlantic ocean, which is brought into the country by the (maritime tropical) MT airmass, a warm moist sea to land seasonal wind. Its warmth and high humidity gives it a strong tendency to ascend and produce copious rainfall, which is a result of the condensation of water vapour in the rapidly rising air.[1]

The Tropical rainforest climate has a very small temperature range. Then temperature ranges are almost constant throughout the year, for example, Warri town in the southern part of Nigeria, records a maximum of 28 °C (82.4 °F) for its hottest month while its lowest temperature is 26 °C (78.8 °F) in its coldest month. The temperature difference of Warri town is not more than 2 °C (5 °F).

The southern part of Nigeria experiences heavy and abundant rainfall. These storms are usually convectional in nature due to the regions proximity, to the equatorial belt. The annual rainfall received in this region is very high, usually above the 2,000 mm (78.7 in) rainfall totals giving for tropical rainforest climates worldwide. Over 4,000 mm (157.5 in) of rainfall is received in the coastal region of Nigeria around the Niger delta area. Bonny town found in the coastal region of the Niger delta area in southern Nigeria receives well over 4,000 mm (157.5 in) of rainfall annually. The rest of the southeast receives between 2,000 and 3,000 mm (118.1 in) of rain per year.

The southern region of Nigeria experiences a double rainfall maxima characterised by two high rainfall peaks, with a short dry season and a longer dry season falling between and after each peaks. The first rainy season begins around March and last to the end of July with a peak in June,this rainy season is followed by a short dry break in August known as the August break which is a short dry season lasting for two to three weeks in August. This break is broken by the Short rainy season starting around early September and lasting to Mid October with a peak period at the end of September. The ending of the short rainy season in October is followed by Long Dry Season. This period starts from late October and lasts till early March with peak dry conditions between early December and late February.[2]

The Tropical savanna climate or Tropical wet and dry climate, is extensive in area and covers most of Western Nigeria to central Nigeria beginning from the Tropical rainforest climate boundary in southern Nigeria to the central part of Nigeria, where it exerts enormous influence on the region.

This climate, the tropical savanna climate exhibits a well marked rainy season and a dry season with a single peak known as the summer maximum due to its distance from the equator. Temperatures are above 18 °C (64 °F) throughout the year. Abuja, Nigeria's capital city found in central Nigeria, has a temperature range of 18.45 °C (65.21 °F) to 36.9 °C (98.4 °F), and an annual rainfall of about 1,500 mm (59.1 in) with a single rainfall maxima in September.[3]

The single Dry season experienced in this climate, the tropical savanna climate in central Nigeria beginning from December to march, is hot and dry with the Harmattan wind, a continental tropical(CT) airmass laden with dust from the Sahara Desert prevailing throughout this period.

With the Intertropical Convergence Zone (ITCZ) swinging northward over West Africa from the Southern Hemisphere in April, heavy showers coming from pre-monsoonal convective clouds mainly in the form of squall lines also known as the north easterlies formed mainly as a result of the interactions of the two dominant airmasses in Nigeria known as the Maritime tropical(south westerlies) and the Continental tropical(north easterlies),[4] begins in central Nigeria while the Monsoons from the south atlantic ocean arrives in central Nigeria in July bringing with it high humidity, heavy cloud cover and heavy rainfall which can be daily occurrence lasting till September when the monsoons gradually begin retreating southward to the southern part of Nigeria.Rainfall totals in central Nigeria varies from 1,100 mm (43.3 in) in the lowlands of the river Niger Benue trough to over 2,000 mm (78.7 in) along the south western escarpment of the Jos Plateau.[5]

The Sahel Climate or Tropical dry climate, is the predominant climate type in the northern part of Nigeria. Annual rainfall totals are lower compared to the southern and central part of Nigeria.
Rainy season in the northern part of Nigeria last for only three to four months (June–September). The rest of the year is hot and dry with temperatures climbing as high as 40 °C (104.0 °F) .

Alpine climate or highland climate or mountain climate, are found on highlands regions in Nigeria. Highlands with the alpine climate in Nigeria, are well over 1,520 metres (4,987 ft) above sea level. Due to their location in the tropics, this elevation is high enough to reach the temperate climate line in the tropics thereby giving the highlands, mountains and the plateau regions standing above this height, a cool mountain climate.

Seasons[edit]

Nigeria, like the rest of West Africa and other tropical lands, has only two seasons. These are the Dry season and the Rainy season. The dry season is accompanied by a dust laden airmass from the Sahara Desert, locally known as Harmattan, or by its main name, The Tropical Continental (CT) airmass , while the rainy season is heavily influenced by an airmass originating from the south atlantic ocean, locally known as the south west wind, or by its main name, The Tropical Maritime (MT) airmass. These two major wind systems in Nigeria are known as the trade winds.

Trade winds[edit]

Tropical Maritime Airmass[edit]

The Tropical Maritime Airmass (MT) is responsible for Nigeria's rainy season. This wind (the Tropical Maritime Airmass) invades the country from February in the southern part of Nigeria while it takes longer for the wind to fully cover the whole of the country, reaching the northern part of Nigeria in June. Its invasion is as a result of the northward retreat, of the tropical continental airmass (CT) known as the harmattan. The northward retreat of the tropical continental airmass (CT), is caused by the sun's northward shift from the tropic of capricorn in the southern hemisphere to the tropic of cancer in the northern hemisphere. This shift begins from February and ends in June, when the sun is fully overhead, at the tropic of cancer in the northern hemisphere.

During this northward migration of the sun as a result of the earth tilting along its axis, the sun crosses the equator (around March), moving over west Africa at this time on its journey to the northern hemisphere. West Africa comes directly under the sun at this time. The sun is overhead throughout west Africa and over Nigeria during this period of the sun's northward migration to the tropic of cancer in the northern hemisphere.

The whole of West Africa is heated intensely as result of the increased insolation received from the sun being overhead over west Africa. Temperatures can climb as high as 35 °C (95.0 °F) over west Africa during this time. Temperatures in the northern part of Nigeria can go as high as 48 °C (118.4 °F) in cities like Maiduguri.[6]

The high temperatures coupled with an increase in insolation causes a region of low pressure to develop over west Africa and Nigeria (between March to May). The Tropical continental airmass (CT) from the Sahara Desert in the northern part of West Africa, is weakened due to the overheating of the land surface in west Africa and Nigeria at this time. The Tropical continental airmass (CT) begins to retreat northwards to the Sahara Desert due to massive heating of the land which transfers heat in the form of convection into the Tropical continental airmass (CT) which constitutes the main layer of air above the land. This transfer of heat in the Tropical continental airmass (CT) in turn, causes the wind to expand and become lighter as this is the normal behaviour for winds moving above intensely heated grounds. The Tropical continental airmass (CT) loses its strength as a major airmass in the region of west Africa and over Nigeria at this time (around February in the southern part of Nigeria to June in northern Nigeria) and begins to retreat coupled with the rising of air in form of convection within this airmass (Tropical continental airmass (CT)), further weakening the dominance of the wind over west Africa and Nigeria. The Tropical continental airmass (CT) finally retreats from most part of Nigeria, and the West African atmosphere around April to May, leaving an empty atmosphere over Nigeria. The sun's rays enters into the atmosphere of Nigeria more intense than it does during the presence of the Tropical continental airmass, which contained dust (in form of haze) that reduced the intensity of the sun.[7] The overheating of the west Africa land mass and Nigeria in particular creates a low pressure region over west Africa and Nigeria. This low pressure zone attracts the Tropical Maritime Airmass (MT) from the south Atlantic Ocean since areas of low pressures experiences inward blowing winds because winds are moving air blowing outwards from regions of high pressure to regions of low pressure.

The Tropical Maritime Airmass is a warm humid and unstable trade wind due to its warmth. Convectional currents are easily set up within the airmass whenever there is little instability in the airmass as a result of a slight to a very high orographic uplift in mountainous regions like the obudu plateau or the heating of the land which can trigger the formation of cumulonimbus cloud leading to thunderstorms within the airmass.

During the dominance of the Tropical Maritime Airmass (MT) in the rainy season of Nigeria, mornings are bright and sunny, the sun's heating of the land in the mornings and afternoons sets up convectional currents, these currents rise vertically and cumulonimbus clouds are formed, by afternoons to evenings, torrential downpour follows.

The Easterly wave or the African easterly waves is another major contributor of rainfall during the summer monsoons months of May to September in Nigeria.

The nature of this waves changes at about the 15 degrees line. The waves that pass south of this line carry moisture and create convection that leads to rain clouds.[8] Nigeria's northern end is south of the 15 degrees line at about 14 degrees.[9] Nigeria's location in the wetter part of the easterly waves south of the 15 degree line creates wetter climatic conditions for Nigeria especially during the monsoons.

Tropical continental airmass[edit]

The Tropical Continental Airmass (CT) locally known as the harmattan, is a wind originating from North Africa which crosses the Sahara Desert into west Africa to Nigeria. This airmass dominates Nigeria's climate during the dry season from December to March. The Tropical continental airmass is dusty and creates a haze within the atmosphere of west Africa and Nigeria when it predominates. The haze is as a result of the dust within the airmass limiting visibility and blocking much of the sun's rays from reaching the earth.

Effects of the tropical continental airmass[edit]

The airmass has no ability of forming rain due to low humidity within the airmass, since it crosses the Sahara Desert, it picks up dust instead of water thereby creating little chances for rainfall.

The airmass makes life difficult as a result of low visibility which hampers transportation. The dust haze creates an almost desert conditions in the country during the dominance of the Tropical continental airmass (the harmattan). But its coming brings some relief to farmers since the low humidity present in the air quickens the drying of their crops.

Temperature[edit]

Nigeria's location in the tropics has given her a tropical hot climate. Temperatures in Nigeria vary according to the seasons of the year as with other lands found in the tropics. Nigeria's seasons are determined by rainfall with rainy season and dry season being the major seasons in Nigeria.

The rainy season of Nigeria brings in cooler weather to the country as a result of an increased cloud cover that acts as a blockage to the intense sunshine of the tropics by blocking much of the suns rays in the rainy season; this in turn cools the land, and the winds above the ground remains cool thereby making for cooler temperatures during the rainy season. But afternoons in the rainy season can be hot and humid, a feature of tropical climates.

The dry season of Nigeria is a period of little cloud cover in the southern part of Nigeria to virtually no cloud cover in the northern part of Nigeria. The sun shines through the atmosphere with little obstructions from the clear skies making the dry season in Nigeria a period of warm weather conditions. In the middle of the dry season around December, a dusty wind from the Sahara Desert called the harmattan enters Nigeria from the northeastern part of the country blocking sun rays partially from shining and also creating haze in the atmosphere, this activities of the wind lowers temperatures considerably saving inhabitants for sometime, from the scorching heat that would have occurred as a result of clearer skies during the dry season. But with the withdrawal of this wind around March to April following the onset of the rainy season, temperatures can go as high as 44 °C (111.2 °F) in some parts of Nigeria.[10]

Semi temperate weather conditions prevail on the highlands in central Nigeria above 1,200 metres (3,937 ft) above sea level, namely the Jos Plateau. Temperatures on the Jos plateau ranges between 21°C to 25°C which are cool all year round.

Temperate weather conditions occur on the highlands along the Nigeria Cameroon border, in the eastern part of Nigeria. Highlands in these region attain an average height of more than 1,524 m (5,000 ft) to some standing above 2,000 metres (6,562 ft) above sea level. The climate on these highlands is temperate all year round. The major highlands in this region are the Obudu Plateau above 1,584 m (5,197 ft), Mambilla Plateau above 1,524 m (5,000 ft) and Mt Chappal Waddi above 2,000 m (6,562 ft).

Topography[edit]

Topography of Nigeria

Nigeria's most expansive topographical region is that of the valleys of the Niger and Benue River valleys (which merge into each other and form a "y" shaped confluence at Lokoja).[11] Plains rise to the north of the valleys. To the southwest of the Niger there is "rugged" highland, and to the southeast of the Benue hills and mountains are found all the way to the border with Cameroon. Coastal plains are found in both the southwest and the southeast.[11]

Niger Delta[edit]

The Niger Delta is located in the southern part of Nigeria. It is one of the world's largest arcuate fan-shaped river deltas.

The riverine area of the Niger Delta is a coastal belt of swamps bordering the Atlantic ocean. The swamps are vegetated tidal flats formed by a reticulate pattern of interconnected meandering creeks and distributaries of the River Niger.

Vegetation of the Niger Delta[edit]

The vegetation of the Niger Delta consist mainly of forest swamps. The forest are of two types, nearest the sea is a belt of saline/brackish Mangrove swamp separated from the sea by sand beach ridges within the mangrove swamp. Numerous sandy islands occur with fresh water vegetation. Fresh water swamps gradually supersede the mangrove on the landward side. About 70% of Nigeria's crude oil and gas production is from the area.

Human population in the Niger Delta[edit]

The riverine area is home to a large population of people living mainly in small villages scattered along the banks of rivers and creeks.

Rainfall in Niger Delta[edit]

Rainfall in the coastal belt of the Niger Delta is heavy due to the closeness of the Delta region to the equator. Annual rainfall totals vary from 2400 to over 4000 millimeters.

Niger Delta cities and their annually rainfall totals in millimeters:

  • Warri — 2,730mm
  • Forcados (coastal town in the Niger Delta) — 4,870mm
  • Port Harcourt — 2,400mm
  • Calabar (coastal city) — 3,070mm (rainiest city with over one million people in Nigeria)
  • Bonny (south of Port Harcourt) — 4,200mm

Vegetation[edit]

Vegetation map of Nigeria.

Nigeria is covered by three types of vegetation: forests (where there is significant tree cover), savannahs (insignificant tree cover, with grasses and flowers located between trees), and montane land. (The latter is the least common, and is mainly found in the mountains near the Cameroon border.) Both the forest zone and the savannah zone are divided into three parts.[12]

Some of the forest zone's most southerly portion, especially around the Niger River and Cross River deltas, is mangrove swamp (see Central African mangroves). North of this is fresh water swamp, containing different vegetation from the salt water mangrove swamps, and north of that is rain forest.[12]

The savannah zone's three categories are divided into mm' Guinean forest-savanna mosaic, made up of plains of tall grass which are interrupted by trees, the most common across the country; Sudan savannah, similar but with shorter grasses and shorter trees; and Sahel savannah patches of grass and sand, found in the northeast.[12]

Natural resources and land use[edit]

Nigeria's natural resources include but are not limited to petroleum (see petroleum in Nigeria), tin, columbite, iron ore, coal, limestone, lead, zinc, natural gas, hydropower, and arable land.

Extreme points[edit]

This is a list of the extreme points of Nigeria, the points that are farther north, south, east or west than any other location.

References[edit]

Coordinates: 10°00′N 8°00′E / 10.00°N 8.00°E / 10.00; 8.00