CLIMATE CHANGE FACTORS AND TYPES

WEEK 8

SUBJECT:    Geography

CLASS:    SS 2   

DATE: ……………………..

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:

(i) 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 faraway at another.

(ii) 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.

(iii)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.

(iv) 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 inland. 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.

(v) CONTINENTALITY: Land surfaces are heated more quickly than water surfaces because of the high specific heat of water. In other words, it requires only one-third as much energy to raise the temperature of a given volume of land by 0.6°C as it does for an equal volume of water. This account for the warmer summer, colder winter and great range of temperature of continental interiors as compared with maritime districts.

(vi) OCEAN CURRENTS: The warm air from the sea keeps the immediate surrounding lowlands warm while the cold currents tend to reduce summer temperature especially the on-shore winds. Cold currents force rain bearing wind to drop most water into the sea. Thereby making the coastal land dry.

(vii)    SLOPE OR ASPECT: A steep slope experiences a more rapid change in temperature than a gentle one. Sun-facing slopes are usually warmer than sheltered slope. In the northern hemisphere for example, south facing slopes are usually warmer than the north facing slopes which are sheltered from the direct influence of the sun. The slopes of mountains facing the direction of the prevailing winds also receive more rain than the leeward side, especially if the prevailing winds are on-shore and moisture laden.

(viii)    CLOUD COVER: Clouds reduce the amount of solar radiation reaching the earth’s surface and the amount of earth radiation leaving the earth’s surface. When there are no clouds both types of radiation are at a maximum. The heavy cloud cover of the equatorial regions explains why the day temperatures rarely exceeds 30°C and why the night temperatures are not much lower. In hot deserts the absence of clouds and the presence of dry air result in very high day temperatures of over 38°C and much lower night temperature of 21°C or below.

(ix) NATURAL VEGETATION AND SOIL: There is a definite difference in temperature between forested region and open ground. It is, in fact, cool in the jungle and its shade temperature is a few degrees lower than that of open spaces in corresponding latitudes. During the day trees lose water by transpiration so that the air above is cooled. Relative humidity increases and some mist and fog may form.

Light soils reflect more heat than darker soils which are better absorbers. Such soil differences may give rise to Slight variations in the temperature of the region. As a whole, dry soils like sands are very sensitive

to temperature changes, whereas wet soils, like clay, retain much moisture and warm up or cool down more slowly.

EVALUATION:

1. List and explain five factors that affect climate.
2. Write short note on the following:  (i) Insolation (ii) Normal lapse rate (iii) Continentality effect on climate.

SUB-TOPIC 2: CLIMATIC TYPES

Climatic types may be basically divided into four while each of the four groups has its sub-groups as outline below:

1. HOT CLIMATE: This climatic types lies between 300N and 300S. The hot climate is sub-divided into four namely; (i) Equatorial climate (ii) Tropical continental, (iii) Tropical monsoon and (iv) Hot deserts.
2. WARM TEMPERATE CLIMATE: This climatic types lies between 300N and 450S. It is sub-divided into (i) Warm Temperate Western Margin and (ii) Warm Temperate Eastern Margin
3. COOL TEMPERATE CLIMATE: This climatic types lies between 450N and 500N. It is sub-divided into (i) Cool Temperate Western Margin, (ii) Cool Temperate Eastern Margin and (iii) Cool Temperate Continental
4. COLD CLIMATE: This climatic types lies between 500N&S and beyond. It is sub-divided into (i) Cold Temperate, (ii) Tundra and (iii) Polar climate.
5. HOT CLIMATE
6. Equatorial Climate

Location: This is located between latitude 50N and 50S of the equator. Area: Amazon basin, Zaire basin, Guinea Coast of West Africa etc. Climatic characteristics

1. Temperature is uniformly high throughout the year with a mean annual temperature of about 270C. ii.        The daily range of temperature is usually between 60C and 80C.

iii.    The annual range of temperature is about 30C.

1. Rainfall is generally high and well distributed throughout the year, usually between 1524mm and 2699mm.
2. There is hardly any month which does not experience rain. vi. The rainfall is usually heavy and convectional.

vii.    The region experience double maximum rainfall which occurs just after the equinoxes (March & September).

viii.    The relative humidity is constantly high usually over 80%.

Human activities

1. Lumbering
2. Plantation Agriculture 3. Hunting
3. Fishing
4. Desert Climate

There are two major types of desert namely hot and cold deserts. i. Hot Desert Climate

Location: The major hot deserts of the world are located on the western coasts of continents within latitude 150 and 300 north and south of the equator. Areas covered by this type of climate include the Sahara desert (North Africa) which is the largest, Arabian desert, Iranian desert etc.

Climatic Characteristics

1. There is high temperate ranges between 300C – 600C.
2. Aridity or rainless is the most outstanding feature of the area. iii. Annual range of temperature is about 90C
3. Annual rainfall is about 250mm. v. High rate of evaporation.
4. Desserts are associated with cold current. vii. The relative humidity is very low.

Human Activities

1. Food gathering e.g. fruits
   
2. Nomadic hunting for wild animals iii. Nomadic pastoral farming
3. Crop production include cotton, rice, sugar cane, millet etc. with the aid of irrigation. ii. Cold Desert Climate

Location: The cold desert climate of the world is located within latitude 450 and 600 north and south of the equator. They are otherwise referred to as the mid-latitude desert. This climate is found in interiors of Eurasia, North America and in Patagonia (South America)

Climatic Characteristics

1. There is hot summer and cold winter.
2. Winters are cold with temperature below 70C while summers are hot (380C). iii. Rainfall in low (25cm) and unreliable due to long distance from the sea.
3. Most rain occurs in late winter and early spring
4. Four seasons are here, autumn, summer, winter and spring.

Human Activities

1. Food gathering ii. Nomadic herding

iii. Little cultivation of crops

1. WARM TEMPERATE CLIMATE: This climatic types lies between latitude 300N and 450S. It is sub-divided into (i) Warm Temperate Western Margin and (ii) Warm Temperate Eastern Margin.
2. COOL TEMPERATE CLIMATE: This climatic types lies between latitude 450N and 600S. It is sub-divided into (i) Cool Temperate Western Margin, (ii) Cool Temperate Eastern Margin and (iii) Cool Temperate Continental
3. COLD CLIMATE: This climatic types lies around 500 North and South and beyond. It is sub-divided into (i) Cold Temperate, (ii) Tundra and (iii) Polar climate.
4. Polar Climate

Location: This climate is found around 900S and N of the equator especially around the north and south poles. These areas of occurrence are Antarctica in the southern hemisphere, Greenland and Iceland in northern hemisphere.

Climatic Characteristics

1. Temperature is generally very low getting below 00C. ii. Annual range of temperature is minimal or negligible.

iii. There is continuous falling of snow.

1. There is no form of vegetation as the land is covered by ice throughout the year.

v.Human habitation is very scarce, except only in Greenland where the Eskimos have naturally survived up to date, living in their Igloos-houses built of solidified or hard blocks of ice.

Human activities

1. Fishing in summer 2. Hunting of wild life
2. Herding of some animals that adapt to cold weather
3. Tundra Climate or Arctic Climate

Location: It is located around the Arctic and Antarctic circles region around latitude 600 and 900 North and South of the equator especially coastal strip of Greenland, north Canada and Alaska etc.

Climatic Characteristics

1. It has long, cold winter and short cool summer
2. The temperatures are low throughout the year with a mean annual temperature normally below 00C. iii. The annual rainfall is about 25cm in summer
3. Presence of snow high incidence of frost and lots of blizzards
4. There is continuous night in winter and continuous day in summer.

Human activities

1. Semi-nomadism is confined to the coast on furbearing animals ii. Fishing in summer
   

iii. Hunting by the Eskimos in Greenland where CARIBON (American deer) is hunted for meat, milk and skin.

EVALUATION

1. Differentiate between the equatorial and the tropical continental climate. 
2. Differentiate between cold desert climate and hot desert climate.
3. State four climatic characteristics of cold temperate climate.

GENERAL EVALUATION

1. Explain the part played by temperature in climate. What are the various factors that affect its distribution round the globe?
2. Write a careful description of the climate of your political region show how the seasons vary throughout the year.
3. Discuss the cold desert climate under these headings: (i) location (ii) climatic characteristics (iii) human activities

WEEKEND ASSIGNMENT

Write notes on Warm Temperate Climate and Cool Temperate Climate.

READING ASSIGNMENT:

Read about the Greek and Koppen’s climatic classification.

REFERENCES TEXTS

1. Certificate Physical and Human Geography for Senior Secondary Schools (New Impression) by O. Areola, K. Ahmed, O.I. Irueghe, B.O Adeleke and G.C. Leong
2. Comprehensive Geography for Senior Secondary Schools (New Edition) by P. Oluwafemi, and S. Ajayi
3. Essential Geography for Senior Secondary Schools by O. A. Iwena 4. Exam Focus Geography for WASSCE and SSCE by O. Areola et al.