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WEEK 8
TOPIC: CLIMATE II
CONTENT:
(1) Climatic Factors
(2) Climatic Types
(3) Characteristics of climate types
(4) Geography distribution of climate types
SUB-TOPIC 1: CLIMATE FACTORS
Climate varies from one part of the world to another due to the effects of the following factors:
- LATITUDE: Latitude here refers to the location of a place in question on the surface of the earth in relation to the equator. The altitude of the midday sun is always high in the tropics and hence temperatures are always high. Outside the tropics the altitude is lower and temperatures are correspondingly lower. In general, temperatures decrease from the equator to the poles. Equatorial regions also have a more constant or equable climate because the sun is always near. On the contrary, there is a much greater seasonal variation at the temperate regions and the poles where the sun is near at one season and far away at another.
- ALTITUDE AND RELIEF: Generally, the higher we go, the cooler it becomes. Therefore the top of plateaux and mountains is usually cooler than their surrounding plains. In general, temperature decreases by 0.65°C for every 100metres of ascent that is 6.5°C for every 1000metres (1km) of ascent, or 1°C for approximately 160metres of ascent. This decrease in temperature with increasing elevation/altitude is called lapse rate or environmental lapse rate. High altitude location usually receives much rain which is called relief or Orographic rain.
- PLANETARY WINDS AND PRESSURE: The land surface is heated more quickly than water surface because of the high specific heat of water. Winds which blow from the sea are generally more moisture – laden than those blowing from the land. This is the reason why the coastal areas of West Africa have heavy rainfalls when the south – west winds are blowing from the Atlantic Ocean than when the North – east wind are blowing from the Sahara region. Pressure belts also have direct effect on winds in the sense that wind blows from area of high pressure to area of low pressure.
- DISTANCE FROM THE SEA: The climate of places close to the sea usually differs from that of places farther inland owing to the moderating influence of the sea which is usually referred to as maritime influence. Coastal areas usually have more equable climate, more rainfall and a longer rainy season than those further inlands. In general, places get progressively drier with distance from the sea and this can be observed in Nigeria as one move from Lagos or Calabar to Maiduguri. Places very far from the sea often experience desert or semi-desert conditions.
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