Explain the main factors that affect temperature and rainfall, including latitude, altitude, distance from the sea and relief

What this dot point is asking

This outcome asks you to explain why temperature and rainfall vary from place to place, using the main factors: latitude, altitude, distance from the sea and relief (mountains). You should also know the three ways rain forms. The central idea is that a place's climate is shaped by where it sits on the Earth and the landscape around it, which together decide how hot and how wet it is.

The answer

Latitude (distance from the Equator)

Latitude is how far a place is from the Equator, and it is the main control on temperature. Near the Equator the Sun is high in the sky, so its energy is concentrated on a small area and temperatures are high all year. Further from the Equator the Sun is lower, so the same energy is spread over a larger area and temperatures are lower. This is why the tropics are hot and the poles are cold.

Altitude (height above sea level)

Altitude affects temperature: it falls as you go higher, by about 6.5 degrees Celsius for every 1,000 metres. This is because the air becomes thinner with height and holds heat less well. So even in the tropics, high mountains can be cold.

Distance from the sea

The sea heats up and cools down more slowly than the land. So coastal places have a smaller temperature range: cooler summers and milder winters, because the sea moderates the temperature. Places far inland have a larger range: hotter in summer and colder in winter. The sea also adds moisture to the air, affecting rainfall.

Relief and the three types of rainfall

Relief (the shape of the land) affects rainfall. Rain forms when moist air rises, cools and condenses. There are three main types:

• Relief (orographic) rainfall: moist air is forced to rise over a mountain, cooling and raining on the windward side, leaving a dry rain shadow on the leeward side.
• Convectional rainfall: strong heating makes air rise rapidly, cool and form towering clouds and heavy showers, common in the tropics in the afternoon.
• Frontal rainfall: warm air rises over cooler air where two air masses meet, giving steady rain (more common outside the tropics).

Examples in context

Example 1. Singapore's hot, humid coast. Singapore is at sea level, very close to the Equator, and surrounded by sea. The high Sun keeps it hot all year, the sea keeps the temperature range tiny and the air humid, and strong daytime heating produces frequent convectional thunderstorms. Its climate is explained directly by latitude, low altitude and being coastal.

Example 2. A rain shadow behind a mountain range. Where moist winds meet a mountain range, the windward side receives heavy relief rainfall while the land beyond, in the rain shadow, is much drier. This pattern, seen behind many tropical mountain ranges, shows how relief alone can make two nearby places very different in rainfall.

Try this

Q1. Explain why temperatures are high near the Equator. [2 marks]

• Cue. The Sun is high in the sky, so its energy is concentrated on a small area, giving high temperatures all year.

Q2. State how temperature changes as altitude increases, and give the approximate rate. [2 marks]

• Cue. Temperature falls with height, by about 6.5 degrees Celsius for every 1,000 metres, because the air is thinner.

Q3. Name the type of rainfall caused by strong heating making air rise rapidly. [1 mark]

• Cue. Convectional rainfall.