Climate

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What is climate?

Key points

Climate is determined by several factors, including , altitude, , and ocean currents.
The Earth can be divided into climate types. These include polar, temperate, Mediterranean, arid, tropical and mountain climates.

What is climate?

Climate refers to the average conditions, such as and , for a given place. It is calculated over a period of around 30 years. Climate tells us the expected conditions. It differs from weather, which is the actual conditions and can change daily. Climate is determined by several factors. These include:

Latitude

At the Equator, the Sun lies directly overhead. At the , the Sun is lower in the sky. Places closer to the Equator are therefore hotter as the Sun’s rays are more concentrated. The movement of air evens out this difference in temperature. This is called . The movement of air is also responsible for differences in precipitation across the globe.

What is global atmospheric circulation?

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Image caption,
The movement of air across the planet occurs in a specific pattern. The whole system is driven by the Equator, which is the hottest part of the Earth. Air moves in six large cells - three in the Northern Hemisphere and three in the Southern Hemisphere. The cells have names - the Hadley cells, the Ferrel cells, and the Polar cells.
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Air rises at the Equator. The rising air eventually reaches the edge of the atmosphere, where it cannot go any further and so it travels to the north and south. This movement forms part of the Hadley cell.
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The air becomes colder and falls back towards the Earth at around 30 ° north and south of the Equator. This is the point where the Hadley cell and Ferrel cells meet. Falling air is usually dry.
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Air rises again at around 60 ° north and south, and falls again at around 90 ° north and south. This is where the Polar cell lies. Rainy parts of the world are found wherever air rises, and dry parts of the world are found wherever air falls.

Altitude

Higher land is cooler and wetter. There is a decrease in air temperature of around 0.6 °C to 0.7 °C for every 100 m gained in height. As air cools, into clouds and then falls as precipitation. This is called relief rainfall.

Continentality and ocean currents

Water heats up and cools down slowly. The sea retains heat during colder months, but remains cool during warmer months. Therefore, places closer to the sea have climates than those inland. This is called. In addition to this, ocean currents can change coastal climates. For example, cold ocean currents bring cooler temperatures and lower rainfall.

Question

How does altitude affect air temperature?

Climate activity

Play this game to learn more about the different climates around the globe.

Global climate types

The surface of planet Earth can be divided according to the climate type that is found in each location. These include:

Polar – cold, dry climates found in the far north and south of the planet, such as Antarctica. Some polar regions are covered in ice and others have vegetation.
Temperate – climates that are not too hot or too cold, such as the UK. Higher levels of precipitation are often found closer to the sea than further inland.
Mediterranean – warm coastal regions between 30° and 45° north and south of the , such as Italy. These climates have hot, dry seasons and milder, wetter seasons.
Arid – dry climates common along the and , where air is usually falling, such as the Sahara desert in north Africa. Few plants can survive within , but some grasses and trees grow in regions.
Tropical – hot and usually wet climates found along the Equator, such as the Amazon rainforest, in Brazil. Air rises here, leading to heavy rainfall. grow in tropical climates.
Mountain – colder climates at high , which can be found anywhere on the planet, such the Andes in South America. Only small plants, such as grasses and , can survive above the .