MAJOR CLIMATIC ZONES OF THE WORLD

After studying this unit, you will be able to:

(a) Know the names of some of the major climatic regions of the world

(b) understand the main characteristics of the climates, factors affecting these climates, factors affecting these characteristics and how each type of climate affects the vegetation of the area

 (c) understand how people’s ways of life are influenced by the climate in each region

 (d) plot the major climatic regions on a world map

 (e)  recognize each type of region on photographs

(f)  appreciate that people’s lifestyles are influenced by the type of weather and climate

(g)  appreciate that this influence is becoming less as technology helps people to overcome difficulties of their climate and as people move into urban areas.

Keywords

• angle of sun
• climate
• equatorial
• humidity
• polar
• rainfall  
• savannah
• seasons
• temperate
• temperature
• tropical
• weather

2.1 Climate of a local area

 You have already discovered in your work for Senior One that there are different types of climate in East Africa. There are many other different types of climate in the rest of the world, some similar to those of East Africa and others different.

You will notice that climates are different because of the different factors that affect them, as you have discussed in the activity above.

2.2 Factors affecting climate.

From the Activity 2.2, you found out that the following factors affect the climates of places in East Africa

• Distance from the Equator: Because the sun always strikes places near the Equator at a high angle, these places are always hot, Places north or south of the Equator are hot for one season when the sun strikes at a high angle, and usually cooler in the other season when the sun strikes at a lower angle.
• Height: You also learnt that, as you go upwards through the atmosphere, the air becomes thinner or less dense. This is because there is less pressure as there is less air above pressing down on the air below. The molecules of the gases in the air are, therefore, more spaced out, so they do not hold heat very easily and the air is colder. This means air temperature decreases with height, usually 6 ° C for every 1,000 metres you go up. Places which are low near the coast are hotter, usually around 30 ° C in daytime. On the plateaus, temperatures are around 23 ° C to 27 ° C in daytime, and on highlands they are gradually lower until they are below freezing point on mountains. Night time temperatures are colder.

Rainfall

This is mainly affected by:

Distance from the Equator: Because places near the Equator are hot, the air rises causing convectional rainfall. Being near the Equator causes rain all throughout the year with two heavy rainy seasons. Away from the Equator there is only one rainy season when the sun is at a high angle, followed by a dry season when the sun is at a lower angle.

Distance from the sea or lake: As winds blow over the sea or lake, they pick up moisture; so, places near the sea or lake will have wet winds causing rainfall and places far away from the sea or take will have dry winds with le rainfall.

Winds: Amount of rain can be affected by the source and path of winds. If they come from the sea or lake at some seasons, they will cause rainfall if they come from inland at other seasons, they will be dry.

Relief: In places which are hilly or mountainous, the air is forced to rise causing relief rainfall on the windward side. On the leeward side of the hills or mountains, the air descends; it is dry and causes little rain.

Any changes made by people to the natural vegetation may also affect the climate. If forests have been cut down, the air will become drier, as there will be less transpiration of water vapor from trees, and so the air and the climate will be drier.

Major climate regions of the World

The factors which affect the climates of East Africa also affect the climates of the whole world.

Figure 2.1: The three major climatic zones of the world

From the map in Figure 2.1, you can observe that there are three types of climatic zones. These are based mainly on their distance from the Equator, which affects their temperatures.

Figure 2.2: Climate at station A

Figure 2.3: Climate at station B

Figure 2.4: Climate at station C

Figure 2.5: Climate at station D

Figure 2.6: Climate at station E

Figure 2.7: Climate at station F

From the graphs, you have observed that the different climate regions experience different amounts of rainfall. You have also noted that the distribution of rainfall also differs. Some climate regions receive rainfall throughout the year while others receive it in a few months. Temperatures also vary in different climate regions. Some climate regions are hot while others are cold. These climate conditions have an influence on the lifestyle of people who live in the different climate regions. You will learn about this later in the chapter.

Tropical climates are closest to the Equator and, therefore, have the highest average temperatures, usually between 20 ° C and 30 ° C every month. They do not have real summer and winter seasons. This is because the sun always strikes the areas near the Equator at a high angle. They are called tropical because the Tropics are lines north and south of the Equator which show the furthest points from the Equator where the sun is overhead for one day per year.

Temperate climates are further from the Equator, so the sun strikes at a lower angle, and it is cooler, with average temperatures usually between 10 ° C and 25 ° C. They have winter and summer seasons winter temperatures may sometimes go below 0 ° C causing snowfall.

At the end of winter, there is a short season called spring. At the end of summer, there is another short season called autumn this is also known as fall. This is a transition from summer to winter.

Polar climates are the furthest from the Equator. They are close to the poles. They also include those poles. Here the sun strikes at a very low angle, so they are always cold. They have cool summers with average temperatures between 15 ° C and below 5 ° C. As you learnt in Senior One, the earth’s axis is tilted. In June, the northern hemisphere is tilted towards the sun and is hot. It is summer season.

The southern hemisphere is tilted away from the sun and is cool. It is winter. In December the southern hemisphere is tilted towards the sun and is hot. It is summer. The northern hemisphere is tilted away from the sun and is cool. It is winter season.

When the earth is tilted away from the sun, it is tilted so far away that places near the north and south poles do not see the sun at all and it is very cold, as low -40 ° or -50 ° C.

As the graphs show, the climates also have differences in rainfall, due to the factors described above. This means that the tropical and temperate climates can be divided further into three types of climate.

Tropical climates: In Senior One you learnt that there are two types of Tropical climates depending on the movements of the Inter – tropical convergence zone: Equatorial climates have two rainy seasons and two less rainy seasons; Savannah climates have one rainy season when the sun is at a high angle. There are also two more types: Desert climates, near the tropics themselves, have almost no rain because the winds blow from the land. Tropical East Coast climates have more rain than the Savannah or Desert because they are on the coast and get rainfall from winds blowing from the sea.

Temperate climates also have three different types. The rainfall depends on the distance from the coasts. Those inland far from the sea have low rainfall and we can call them Temperate Inland or Interior climates. These areas have short grass with no trees. Those near the coasts have more rain and can be called Temperate East Coast and Temperate West Coast. These areas have forests, but not as thick as equatorial forests. Polar climates all have low rainfall because the very cold air contains little water vapor. These areas have very short grass or ice and snow with no vegetation.

You have noticed that Africa is divided into more than the three climate zones of the world. You have also noticed that countries in the extreme north and extreme south experience temperate climate. Countries in the central part of Africa experience Equatorial climate.

Note: The climatic regions described here and shown on the map in Figure 2.1 are very simplified. There are many other regions which can be used and later you will see maps, diagrams and descriptions with more divisions.

Figure 2.8: Vegetation 1

Figure 2.9: Vegetation 2

Figure 2.10: Vegetation 3

Figure 2.11: Vegetation 4

Figure 2.12: Vegetation 5

Figure 2.13: Vegetation 6

Vegetation depends on rainfall and temperature. Places with heavy rainfall and high temperatures have thick forests; places with moderate or heavy rainfall but cooler temperatures have less thick forests: places with low rainfall have grassland with some trees where the temperatures are higher, but few or no trees in cooler places.

Influence of climate on people’s way of life

Earlier in this chapter you discussed how climate influences people’s way of life in Uganda. You also learnt that there are areas which are dry and others which are cold.

Figure 2.14: Settlement A

 Figure 2.15: Settlement B

You have probably observed that the areas shown in the s photographs are from the hot temperate climate and des climate you also noticed that one of the places is hot while s other is cold. The people who live in these areas have a challenge of extreme temperatures. However, with technology life can tie made better. Air conditioning can be used to heat or cool home Technology can help people in hot deserts to carry out agriculture by using irrigation.

Unit Summary

In this unit, you have learnt that:

• the factors that affect the climates of East Africa also affect all climates of the world.
• the main factors are:
  • Distance from the Equator
  • The angle of the sun’s rays and seasonal changes
  • Height and relief Winds
  • Distance from the water bodies
  • Wind movement
• there are three broad climatic regions with different temperatures namely: Tropical, Temperate and Polar
• these are also affected by distance from the sea and wind movement causing differences in rainfall.
• each kind of climate has a different kind of natural vegetation. The climate affects the way people live.
• the climate affects vegetation of a given area.
• once climate affects vegetation, vegetation in turn also affects the way people live, especially the traditional livelihood.