Factors Affecting the Climate of Africa Latitude: Latitude refers to the location of a place…
CLASSIFICATION OF CLIMATE
Classification of climate is a conscious attempt at group different climates with similar characteristics together. This is because climate varies from place to place. The common systems of classification of climate include the Greeks and Koppen’s classifications.
Greek System of Classification of Climate
This is one of the earliest, ordinary, simple and rough climatic classifications put forward by the Greek people. The basis for the Greek classification is Temperature.
This system divides the world into three climatic zones which include:
- Torrid zone
- This zone is found within the tropics.
- The zone is very hot.
- It has high temperature throughout the year.
- Temperate zone
- This zone is found between the torrid and frigid zone.
- It has mild or moderate temperatures.
- It has seasonal contrasts in temperature.
- Frigid zone
- This zone is found in the Polar Regions (arctic and Antarctic) regions.
- The zone is generally cold with low temperatures throughout the year.
- It has lots of ice-caps in the greater larger part of the year.
These zones were divided by lines of the tropics and the polar circles. The method only emphasizes temperature, leaving out other climatic factors. The method is very subjective and not very useful in modern times.
Criticism of Greek Classification
- It was based only on temperature, leaving out other climatic elements.
- It was too simple.
- It ignores the influence of latitude and altitude, presence of vegetation and wind system.
- It fails to recognize climates such as those of the humid and the desert regions.
Koppen’s System of Classification of Climate
The best known system of climatic classification was the one devised by Dr. Wladimir Koppen of the University of Graz (Austria) in 1918.
The basis for Koppen’s classification is temperature and rainfall (precipitation). He identified five major climatic groups which correspond with the five principal vegetation groups. They are represented by capital letters as follows:
A – Tropical rainy climate
- This is a moist and hot climate.
- It has average monthly temperature above 18˚C.
- It has heavy rainfall throughout the year which exceeds annual evaporation.
B – Dry climates
- The annual evaporation exceeds annual rainfall.
- It lacks surplus water and aridity is pronounced.
- No river flows permanently in this region.
C – Warm temperate rainy climate (Humid mesothermal climates)
- The average temperature of the coldest month is below 18˚C but above -3˚C.
- The average temperature of the warmest month is over 10˚C.
- It has both summer and winter seasons.
D – Snowy and cold climates (cold snow forest climate)
- The average temperature of the coldest month is below -3˚C.
- The average warmest month is above 10˚C.
- It has frozen ground and snow cover for several months duration.
E – Polar climates (Ice climate)
- The average temperature of the warmest month is below 10˚C.
- There is lack of warm season.
- Precipitation is in form of snow.
These five major climatic groups described above are further subdivided into different sub-groups for each of the climates thus:
A has AF, Am and Aw sub-groups.
B has BS and BW sub-groups.
C has Cw, Cs and Cf sub-groups.
D has Df and Dw sub-groups.
E has ET and ET sub-groups.
Guide to Understanding the Climate Sub-groups
The small letters f,s,w and m reflect how seasonal precipitation is and they mean the following:
f= no dry season generally.
s= no dry season in summer.
w= no dry season in winter.
m= moderate dry season in winter and summer.
The capital letters of S and W show the two sub-divisions of dry climates.
S= mean Steppe or semi desert.
W= mean desert or arid.
In Polar climates
T= means Tundra.
F= means Ice Cap.
Details of the different sub-groups
Only A and B climates are discussed in details note.
A – CLIMATES (TROPICAL RAINY CLIMATES)
There are three sub-groups of the A – Climates. These are Af, Am and Aw.
- Af = Tropical Rain Forest Climate: This climate is located within 5˚ North and South of the equator.
- Amazon Basin of South America.
- The Zaire Basin of Central Africa.
- The coasts of West Africa.
Features of the climate type are:
- Temperatures are high and uniform throughout the year.
- Mean monthly temperature is 27˚C.
- Annual range of temperature is about 30˚C.
- Diurnal range is between 6˚C and 8˚C.
- There is rainfall throughout the year.
- Amount of rainfall is between 1500mm to 2000mm.
- There are double maxima (two peaks of rainfall).
- Rainfall is mainly convectional.
- Humidity is 70 – 80% throughout the year.
- Am = Tropical Monsoon Climate: This climate is located within Latitude 10˚ and 35˚ North and South of the equator.
- Monsoon Asia, including India, Pakistan, Bangladesh, Burma, Thailand, South East and Eastern Asia.
- Northern Australia.
- Central America, West Indies and parts of the coast of Brazil.
- Parts of the Coast of East Africa and West Africa.
- High temperature of about 27˚C.
- Temperature range is 6˚C.
- High annual rainfall of about 1500mm.
- There is concentration of rain in rainy season.
- There is alternating wet and dry seasons.
- Aw = Tropical Grassland of Savanna: This is located within 5˚ – 25˚ north and 5˚ – 20˚ south of the equator.
- Central America.
- North West of South America.
- Interior uplands of Brazil, Bolivia and Paraguay.
- South Central and Eastern Africa.
- West Africa.
- West Malaysia.
- Parts of India and South East Asia.
- Northern Australia.
- Temperatures are more extremely 21˚C – 30˚C.
- Higher range of temperature of 9˚C.
- Rainfall between 250mm – 1500mm.
- Rainfall is seasonal, mainly in summer.
- Rainfall is mainly convectional – single maximum.
B – CLIMATES (DRY CLIMATES)
There are two sub-groups of the B – Climates. These are BS and BW.
- BS = Steppe (Semi –Arid) Climate: This climate is located within 30˚ – 40˚ north and south of the equator.
Areas: Italy, Argentina, Uruguay, South Africa and Australia.
- There are extreme of temperatures – cold winter and hot summer.
- It has temperature of 19˚C – 42˚C.
- Annual range of temperature is 40˚C.
- Annual rainfall is 508mm in summer.
- The relative humidity is very low.
- BW = Desert (Arid) Climate: Found in western coasts of continents 15˚N – 30˚N of the equator.
Areas: West Africa, South Africa, Australia, Saudi Arabia, Namibia and Iran.
- High temperature between 30˚C and 58˚C.
- Temperature range is 11˚C.
- Low annual rainfall of 150mm.
- The zone is blown by cold currents.
- It has low relative humidity.
C – CLIMATES (WARM TEMPERATE RAINY CLIMATE)
There are three sub-groups of the climates. These are Cf, Cw and Cs.
- Cf = Mild humid climate: It has no dry season with the least month of rainfall having 30mm.
- Cw = Mild humid climate: It has a dry winter with heavy rainfall in summer.
- Cs = Mild humid climate: It has dry summer with heavy rainfall in winter.
D – CLIMATES (SNOWY AND COLD CLIMATES)
There are two sub-groups in the D – climates. These are Df and Dw.
- Df = Snowy forest climate: It has winter, no dry season with cold climate.
- Dw = Snowy forest climate: It has dry winter with very cold climate.
E – CLIMATES (POLAR CLIMATE)
The E – Climate has two sub-groups. These are ET and EF.
- ET = Tundra Climate: Average temperature of the warmest month is less than 10˚C but greater than 0˚C.
- EF = Continuous frost Climate: Average temperature of all the months is less than 0˚C. It has ice caps and is found in extremes of north and south poles.
Advantages of Koppen’s Classification
The Koppen’s system of classification is widely accepted over other systems because:
- It is very simple to understand.
- It is objective.
- It is quantitative because, numerical values are used for defining boundaries of climatic groups.
- It is commonly used in teaching at various levels of educational institutions.
Disadvantages of Koppen’s classification
- It did not consider the climate of highlands.
- Letters used are too many and confusing.
- There is no clear distinction of one climate from another.
- Greek’s climate classification is based solely on temperature while Koppen’s is based on climate and vegetation.
- Greek’s climate classification has three major belts while Koppen’s classification has five major climatic types.
- Koppen’s employs quantitative approach in the classification while, Greek’s employs descriptive approach.
- Greek’s classification does not recognize sub-groups, whereas Koppen’s recognizes various sub-groups.