Download ARC 309 GROUP 23

AN ASSIGNMENT
ON
CLIMATIC ZONES FOR ARCHITECTURAL DESIGN WITH CLIMATES
IN NIGERIA. (GROUP 23)
BY
OLADUNJOYE OLUWAYEMI A
ARC/05/5629
ADEPOJU TIWALADE A
ARC/05/5576
OLUBOYEDE DAVID O
ARC/05/5638
DEPARTMENT OF ARCHITECTURE,
FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE
SUBMITTED TO
PROF. OGUNSOTE O.
DEPARTMENT OF ARCHITECTURE FEDERAL UNIVERSITY OF
TECHNOLOGY, AKURE
MARCH 2008
INTRODUCTION
The climate of Nigeria is characterized by two distinct seasons, the Dry and the Wet seasons. On
the average, the rainy season starts in April and lasts till October; the remaining part of the year
is the dry season.
In practice, however, the length of the seasons depend on how near or far they are from the sea.
Notably, therefore, there is a higher period of rain in the parts closest to the sea and the intensity
of rain there exceeds the intensity of rain in the parts further from the sea. A typical example
would be the \Niger-Delta region in the South-West of Nigeria. In contrast to the rains in other
parts, the rainy period s may exceed October or they may begin before April.
Due to this sort of variation, the regions have been classified into the various climatic
zones/areas. Some of these classifications are:
o Equatorial climate
o Tropical Hinterland
o Tropical Continental
o Sahel Climate
o High Plateau Climate
EQUITORIAL CLIMATE
This is at times called sub-equatorial climate. It has characteristics of high temperatures and
heavy rainfall. Rainfalls throughout the year, with an annual total of over 1500mm; no month has
rainfall of less than less than 250mm. there are two peak periods of particularly heavy rain, one
in July and the other in September in-between is the period of relatively low rainfall called
“August Break”. The rainfall is therefore said to be double maxima in character. Humility is
high; the relative humidity is on average about 80%. The temperature is uniformly high
throughout the year at about 27oC and the annual range is very small just about 2oC or 3oC.
The term sub equatorial climate is at times used to describe the climate, especially if the
conditions deviate a bit from what is described above. For example, there may be a pronounced
dry season of about two months, whereas, in the True Equatorial, there is no dry season. Also
there may be a mean annual temperature range of about 4oC or 5oC whereas, in a True
Equatorial, the maximum range is usually 3oC. Ibadan, with an annual temperature range of 4oC,
may be taken as an example of such a location. It, also, has a very low rainfall of only 10mm per
month in December and January. Lagos also has an annual temperature range of 4oC
TROPICAL HINTERLAND CLIMATE (Guinea Climate)
Nigeria enjoys the humid tropical climate type. Because of its location just north of the equator,
Nigeria enjoys a truly tropical climate characterised by the hot and wet conditions associated
with the movement of the Inter-Tropical Convergence Zone (ITCZ) north and south of the
equator.
The country experiences consistently high temperatures all year round. Since temperature varies
only slightly, rainfall distribution, over space and time, becomes the single most important factor
in distinguishing the seasons and climatic regions. Rainfall occurrence and distribution are
however dependent on the two air masses that prevail over the country. Their influences are
directly linked to the movement of the ITCZ, north and south of the equator.
The two air masses are the Tropical maritime (Tm) and the Tropical continental (Tc). The former
is associated with the moisture-laden south-west winds (south westerlies) which blow from the
Atlantic Ocean, while the latter is associated with the dry and dusty north-east winds (easterlies)
which blow from the Sahara Desert. When the ITCZ, the zone of convergence of the two air
masses, is to the south of the equator, the north-east winds prevail over Nigeria, thus producing
the dry-season conditions.
Conversely, with the movement of the ITCZ into the Northern Hemisphere, the rain-bearing
south westerlies prevail as far inland as possible to bring rain fall during the wet season. The
implication is that there is a prolonged rainy season in the far south, while the far north
undergoes long dry periods annually. Nigeria, therefore, has two major seasons, the dry season
and the wet season, the lengths of which vary from north to south.
The seasonal pattern of climatic conditions over Nigeria gives rise to four seasons in the south
and two in the north. This is the result of annual total rainfall occurrence and distribution, which
is more predominant in the south than in the north. The mean annual rainfall along the coast in
the south- east is 4000mm while it is only 500mm in the north- east.
Southern Nigeria: The four observed seasons are:
(i) The Long Rainy Season: This starts in March and lasts to the end of July, with a peak period
in June over most parts of southern Nigeria. It is a period of thick clouds and is excessively wet
particularly in the Niger Delta and the coastal lowlands. It is marked by humidity with values
hardly below 85 per cent in most parts of the forested south.
(ii) The Short Dry Season: This is experienced in August for 3-4 weeks. However, the real dry
period known as the "August break" is generally observed in the last two weeks of August in
most parts of southern “Nigeria".
(iii)The Short Rainy Season: This brief wet period follows the "August break" from early
September to mid-October, with a peak period at the end of September. The rains are not usually
as heavy as those in the long rainy season, although the spatial coverage over southern Nigeria is
similar. The two periods of rainfall intensity give the double maxima phenomenon of the rainy
season characteristic of southern Nigeria. The short dry season in August between these two
rainy periods allows for harvesting and planting of fast-growing varieties of grains, such as
maize.
(iv) The Long Dry Season: This period starts from late October and lasts to early March with
peak dry conditions between early December and late February. The period witnesses the
prevailing influences of the dry and dusty north-east winds, as well as the 'harmattan' conditions.
Vegetation growth is generally hampered, grasses dry and leaves fall from deciduous trees due to
reduced moisture.
Northern Nigeria: The climatic conditions in the northern part of Nigeria exhibit only two
different seasons, namely, a short wet season and a prolonged dry season. Temperatures during
the day remain constantly high while humidity is relatively low throughout the year, with little or
no cloud cover. There are, however, wide diurnal ranges in temperature (between nights and
days) particularly in the very hot months. The mean monthly temperatures during the day exceed
36°C while the mean monthly temperatures at night fall, at most times, to below 22°C.
(i) The Long Dry Season: This period extends from October to mid-May. With the ITCZ in the
Southern Hemisphere, the north-east winds and their associated easterlies over the Sahara prevail
over the country, bringing dry conditions. The harmattan period during December- January is
more intense and longer in the north than in the south. This is the period of little or no cloud
cover, resulting in wide diurnal ranges of temperature .
(ii) The Wet Season: The wet season covers a relatively short period, from June to September.
Both the number of rain days and total annual rainfall decrease progressively from the south to
the north. The rains are generally convectional, heavy and short in duration, often characterised
by frequent storms. This results in flash floods, and in some places also in sheet or gully erosion.
The few high plateaus of Jos and Biu, and the Adamawa highlands, experience climatic
conditions which are markedly different from the generalized dry and wet period in northern
Nigeria. Temperatures are 5 - 10°C lower due to high altitude than in the surrounding areas.
Similarly, the annual rainfall figures are higher than in areas around them, particularly on the
windward side.
Nigeria can, thus, be broadly divided into the following climatic regions:
(a) The humid sub-equatorial, in the southern lowlands
(b) The hot tropical continental, in the far north
(c) The moderated sub-temperate in the high plateaus and mountains
(d) The hot, wet tropical, in the hinterland (the middle-belt)
TROPICAL CONTINENTAL CLIMATE
This is found in the Sudan Savanna. It is found in the north-west stretching from the Sokoto
plains in the west, through the northern sections of the central highland. Its features are found in
almost all the northern states bordering the Niger Republic and covers over one quarter of
Nigeria's total area. The low annual rainfall of usually less than 1000 mm and the prolonged dry
season (6-9 months) sustain fewer trees and shorter grasses than the Guinea savannah. It is
characterized by abundant short grasses of 1.5-2m and few stunted trees hardly above 15m.It is
by far the most densely human populated zone of northern Nigeria. Thus, the vegetation has
undergone severe destruction in the process of clearing land for the cultivation of important
economic crops such as cotton, millet, maize and wheat. This is in addition to devastation due to
animal husbandry, especially cattle rearing, which is greatly favoured in this belt because the
area is relatively free from tse-tse fly. The trees of the Sudan savannah include the acacia, the
shea-butter, baobab and the silk cotton.
It is hot for most of the year, with some months (especially just before the rainy season)
recording temperatures of up to 30oC. The months of January and February are a bit cool, with
temperatures a bit above 20oC; this is due to the influence of the harmattan.
The mean annual temperature range is about 10oC, relative humidity is about 40%.
SAHEL CLIMATE
This is a semi-desert climate, found in the extreme North-East of the country, close to Lake
Chad, where the dry season lasts for up to 9 months and the total annual rainfall is hardly up to
700mm. It is characterized by very short grasses of not more than one metre high located inbetween sand dunes. The area is dominated by several varieties of the acacia and date- palms.
The Lake Chad basin, with its seasonally flooded undulating plains, supports a few tall trees. At
the same time, the drainage system of rivers and streams into the Lake Chad basin has favoured
irrigation, without which cultivation would be virtually impossible. The increasing aridity in the
area accounts for the progressive drying up of the Lake Chad.
The rainy season is just about three months (June to August), and annual rainfall varies form
250m to 500mm. Mean daily temperatures are above 30oC, especially just before the rain, when
afternoon temperature reaches nearly 40oC. But mean monthly temperatures are brought down to
a little over 20oC during the harmattan months of December, January and February. Relative
humidity is very low (about 20%).
HIGH PLATEAU CLIMATE
The mountain vegetation of the isolated high mountains and plateaus of the central and eastern
part of Nigeria is not well developed because of the great influence and interference by man and
animals. For instance, the Jos plateau, which is one of the highest points in Nigeria, is in a
grassland zone, but its vegetation depicts grassland at the top and base of the Plateau, while the
slopes, favoured by moisture-laden wind, are covered by forests. These are also true of the
Mandara and Adamawa mountains and the Obudu plateau.
FACTORS AFFECTING CLIMATE
The three major factors affecting the climate of Nigeria are:
o Distance from sea
o Air masses
o Altitude
Distance from the sea: This has a great influence on the climate. Places near the sea have a more
equable climate; they experience a heavier rainfall and a longer rainy season. The more we move
away from the sea, the more the decline in equability, amount of rainfall and length of the rainy
season.
Air masses: The two prevailing air masses affecting the country are Tropical Maritime Air Mass
and Tropical Continental Air Mass. When the Maritime air mass is prevailing, rainy season is
experienced. When the continental air mass is prevailing, dry season is experienced. The
continental air mass blowing from the Sahara also brings harmattan between December and
February, especially to northern Nigeria.
Altitude: High altitude locations such as Jos Plateau and the Eastern border highlands (Mandara
and Adamawa highlands, Obudu and Mambila plateux) have a cooler and rainier climate than
their surrounding lowlands.
INTER-TROPICAL DISCONTINUITY.
ARCHITECTURAL DESIGN IN THE CLIMATES
Nigeria, as shown in the volume of this discourse, has within its boarders several climatic zones
and features. Needless to say, the variations in the climatic features cannot be exhausted in this
study, but there are cross-sectional features that are observable in all the regions/areas.
SUNSHINE:
Among many others is the fact that Nigeria has a lot of sunshine, being a sub-Saharan country.
Sunshine, therefore is a basic consideration in every work of architecture. Over the years, it has
been proved that buildings erected without due consideration for sunshine end up a liability to
the inhabitants, and more, embarrassments to architecture (Having a lot of dark spaces, etc.).
TEMPERATURE:
Being a tropical country, Nigeria in contras with the temperatures has a high average
temperature. This is largely due to the amount of radial heat absorbed when the sun shines. This
is due to the orientation of the earth to the sun.
In comparism with Europe and America, Nigeria is hot, and so there is need for constant
movement of air within a building. Thermal comfort, therefore, it is always an important factor
in Nigerian design. Notable, the degree varies with the regions.
VENTILATION
Sunshine and high temperature make compulsory for the ventilatory properties of a building to
be considered. The movement of air in a building will affect thermal comfort. Therefore,
building in Nigeria has larger windows than those in South Africa. And even within Nigeria,
building in Lagos may not have had many windows as those in Kano, or Sokoto.
RAINFALL
This is also an important factor of effective designing in Nigeria. For instance, some buildings in
northern Nigeria were erected with flat roofs decades ago. However, need arose with time for
alternative roofs to be erected, due to the emergent leakage of the roofs.
It is therefore important to have slopes in the roofs of building in Nigeria, especially in the
southern Nigeria.
VEGETATION
The vegetation in an area always affects what kind of buildings will be appropriate there when
trees are available, they freshen the air and they serve as wind breakers. Also they affect the
aesthetic outlook of works of architecture, making them blend with nature impeccably.
HUMIDITY
The term humidity is usually taken in daily language to refer to relative humidity. Relative
humidity is defined as the amount of water vapor in a sample of air compared to the maximum
amount of water vapor the air can hold at any specific temperature in a form of 1 to 100%.
Humidity may also be expressed as Absolute humidity and specific humidity. Relative humidity
is an important metric used in forecasting weather. Humidity indicates the likelihood of
precipitation, dew, or fog. High humidity makes people feel hotter outside in the summer
because it reduces the effectiveness of sweating to cool the body by preventing the evaporation
of perspiration from the skin. This effect is calculated in a heat index table. Warm water vapor
has more thermal energy than cool water vapor and therefore more of it evaporates into warm air
than into cold air.
SPEED
How fast wind moves will have an effect on how deep the foundation will go, as well as, what
materials will be used to erect such buildings.
DIRECTION
The direction of wind movement affects how a building should be oriented on site or how the
spaces in the building should be oriented, for instance, kitchen, bedrooms, etc.
CONCLUSION
The study of the climatic zones in Nigeria is a very vital issue when dealing with the design
process in the country, owing to the different regions, it has become very necessary that deep
study be encouraged.
This write up has been able to work to some extent on the issues that should be considered when
dealing with the design process in this part of the world.
REFERENCES

http://en.wikipedia.org/wiki/Humidity

www.pickatrail.com/jupiter/map/nigeria.html

www.springerlink.com/index/rv81k44jq2372237.pdf

http://www.onlinenigeria.com/links/adv.asp?

Senior secondary geography, 1996,geographical Bureau Nigeria limited