Mountains (relief) Mountains affect both temperature and rainfall.


It is colder at the top of a mountain or mountain range than at the bottom because temperature decreases with altitude. The top of the mountain might not always be high enough for snow to fall on it, but it will be colder than its base. This is why there is often snow at the top of a mountain while its base is clear. Look again at the picture of Mount Kilimanjaro on page 51.


If a warm, moist wind blows from the ocean toward a mountain range, it often brings rain to the side of the mountains facing the wind – the windward side. This is because air is forced to rise over the mountains, and so cools and condenses. The air then descends on the other side of the mountains, the leeward side. This air is dry and no or little rain falls on the leeward side. The land on the leeward side of a mountain is said to be in the rainshadow of the mountains. Look at the illustration below to help you understand the effect of relief on rainfall.


New words


windward: the side of a mountain against which the wind blows


descends: goes down


leeward: the side of a mountain that is sheltered from the wind


rainshadow: a dry area on the leeward side of a mountain


relief: variation in elevation of land surface; land having flat parts and mountainous parts


The effects of mountains on rainfall Activity 2 Explain how geographical position affects climate


1 Many people go skiing in the Swiss Alps. These mountains are more than 2 000 m above sea level. Which factor affecting temperature can explain why it is cold enough to snow in the Alps?


2 Antarctica is covered in ice all year. Which factor affecting temperature can explain why it is so cold there?


3 Manaus, on the equator in South America, has heavy rain all year, and very high temperatures. Which factor affecting temperature and rainfall can explain these conditions?


4 Look at the map of Australia on the right. 4.1 Do you think places on the east or the west coast will have higher temperatures?


4.2 Give the reason for your answer. 4.3 Where will there be less rainfall: on the eastern or western sides of the Great Dividing range?


4.4 Draw a well-labelled sketch to explain why the side of the range you noted in Question 4.3 is drier than the other side.


Map of Australia Unit 1 Factors that influence temperature and rainfall 53


TERM 2


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