You have learnt that prevailing weather conditions form the climate of a particular place over a period of time (20 – 35 years). As the weather is unpredictable, we are not able to say for sure that it will rain in Cape Town on New Year’s Day, but we do know that Cape Town will normally be drier at this time of the year than in June. Climatic conditions over a long period of time have shown that Cape Town receives most of its rain during the winter.

When we study the features of the types of climate that prevail in places, it is clear that large areas experience the same average conditions and that a type of climatic region is therefore formed. Through the ages people have often been influenced by the climate when they must to decide where they want to settle. Large parts of the earth are either too cold, or dry or hot for people to live. The availability of sources also influences peoples’ choice of a place to live. That is why approximately six milliard people on earth occupy only 15% of the earth’s surface.

1. Factors that influence climate

Latitude of a place

The hottest climates are usually in places closest to the Equator. The further we move from the Equator, the colder it becomes. At 12:00 the sun is directly overhead on the Equator. The rays of the sun are more concentrated and the temperatures rise higher. Further north and south the rays of the sun fall at an angle and are spread over a larger area by the earth’s rounded shape. That is why the sun’s rays are less concentrated and as a result the temperatures are cooler.

Figure 1

At the equator the sun’s rays are almost directly overhead.

At the poles the sun islower on the horizon.

At the Equator high temperatures cause high evaporation, which causes a higher downpour.

Altitude above sea level

The earth absorbs the sun’s rays, converts them to heat and radiates them again. The closer we are to the source of radiation, the hotter it is, and the further we are from the source (e.g. on top of a mountain), the colder it becomes. We can experience the principle of radiation by holding our hands close to a fire (or heater) and then move them away gradually. It becomes colder the further we move away from the source.

It is always cold on top of high mountains. The highest mountain peaks on the earth are always covered with snow.

Use your atlas to find out:

Influence of ocean currents/oceans

The temperatures of the oceans influence the land temperatures. Winds blow the hot or cold air above the hot or cold ocean towards the land and increase or reduce the land temperatures. There are also winds that blow north and southwards from the Polar Regions bringing cold air onto the land.

Water has a larger heat retention capacity than the land has. The water, however, takes longer to heat during the day. Therefore the land reaches higher day temperatures than the water. The sea then has a “cool” influence from the sea to the land. During the night the land cools down much faster than the water, which then causes a “warm” influence from the sea to the land.

The result is that places along the coast or large water masses, experience a moderate temperature. The margin between maximum and minimum is not very big.

Hot water evaporates faster and better than cold water. There is more evaporation above a warm sea current. This results in a higher precipitation in areas that border on warm sea currents.

Relief

In grade 5 we learnt that the escarpment diverts the rain bearing winds and clouds away from the interior. Mountains also have a sunny side and a shady side. The sunny sides have higher average temperatures, and the shady sides have lower average temperatures.

2. Climate and vegetation

Study the climatic information in the table on page 15 and answer the following questions:

Table 1: Climatic information for Belèm and Singapore

Activity 1:

Activity 2: