Climate Characteristics (Cambridge (CIE) IGCSE Geography)

Revision Note

Bridgette Barrett

Written by: Bridgette Barrett

Reviewed by: Jenna Quinn

Equatorial Climate Characteristics

World climate distribution

  • Climates vary across the world

  • The reasons for these climate types include:

    • Latitude

      • With distance from the equator temperatures and sunshine hours decrease as the solar radiation is more dispersed at the poles and it has to pass through a greater amount of atmosphere

    • Altitude

      •  Increases in altitude lead to decreases in temperature 

    • Continentality

      • Locations further inland heat up more quickly in the summer and cool more quickly in the winter

    • Ocean currents

      • Warm and cold currents circulate in the oceans either warming or cooling the adjacent land 

    • Aspect

      • In the northern hemisphere slopes facing south are warmer 

    • Prevailing winds

      • Winds coming from warmer areas bring warmer air, increasing temperatures

    • Pressure systems

      • Areas usually affected by low pressure such as the equator have rising air, condensation, and cloud formation leading to more precipitation

      • Areas affected by high pressure have dry conditions due to the sinking air

Equatorial climate distribution

distribution-of-the-equatorial-climate
Distribution of the Equatorial Climate

Equatorial climate characteristics

Location

  • Low latitudes

  • Within the Tropics 23.5° north and south of the equator

  • Amazon in South America, New Guinea, South-east Asia, Zaire Basin

Annual precipitation

  • Over 2000mm

Temperature range

  • Low range of mean monthly temperatures - 26-28°C

  • Constant high temperatures 

  • Diurnal range is about 7oC

Seasons

  • No seasons - hot and wet all year round

Humidity

  • High, usually over 75-80%

Prevailing winds

  • Winds blow into the equatorial region from high-pressure areas to the north and south. 

  • The winds from the north blow from the north-east and the winds from the south blow from the south-east.

  • The winds are known as the trade winds

climate-graph-for-iquitos-peru
Climate graph for Iquitos, Peru

Factors influencing the equatorial climate

  • There are a range of factors that influence the climate including:

    • The midday sun is almost directly overhead all year meaning there is maximum insolation

    • Low pressure all year leads to rising air, condensation, cloud formation, and high precipitation levels

    • Dense vegetation cover leads to high levels of evaporation and transpiration 

    • The warm air stores large amounts of water vapour until the temperatures start to cool in the late afternoon which then leads to heavy, daily convectional rainfall

Hot Desert Climate Characteristics

Hot desert climate distribution

distribution-of-hot-deserts
Distribution of the Hot Desert Climate

Hot desert climate characteristics

Location

  • 15° - 30° north and south of the equator (tropical and sub-tropical)

  • North Africa - Sahara, Southern Africa - Kalahari and Namib, Australia. Middle East

Annual precipitation

  • Below 250mm

Temperature range

  • Daytime temperatures can reach 50°C but average around 25°C

  • Night-time temperatures below 0°C

  • The diurnal range is large up to 45°C

  • The annual range is around 15°C

Seasons

  • Summer and winter

Humidity

  • Low often between 10-30%

Prevailing winds

  • The winds are offshore blowing from the east across the land, so they do not collect any moisture

climate-graph-for-jeddah-saudi-arabia
Climate Graph for Jeddah, Saudi Arabia

Factors influencing the hot desert climate

  • High pressure all year means the air is descending and warming

    • Precipitation does not occur because the air is not rising

  • Prevailing winds are often from over land masses which means they contain little moisture

  • Some deserts are in a rain shadow so there is little rainfall

  • Cold ocean currents on the west side of continents may reduce summer temperatures due to the cooling effect of the ocean

Influence of pressure systems

  • Hot deserts form between 15o- 30o north and south of the equator as a result of the atmospheric pressure systems

    • Air rises at the equator and when it reaches the upper atmosphere it moves north and south

    • The air cools and starts to sink

    • This creates a zone of high pressure at about 30o north and south of the equator

    • Due to the sinking air, warm air cannot rise, condense, and form clouds. This results in high aridity

Diagram of Earth's atmospheric circulation showing equator, tropics, deserts at 30 degrees north and south, rising warm air at low pressure, and sinking cool air at high pressure.
Atmospheric Pressure Systems

Worked Example

Explain how high atmospheric pressure influences the climate of hot deserts. 

[3 Marks]

Answer

  • Air is descending [1]

  • It heats up/does not cool  [1]

  • Condensation does not occur/clouds do not form  [1]

  • Precipitation is low/does not occur/drier/only has e.g. 250 mm per annum etc  [1]

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Bridgette Barrett

Author: Bridgette Barrett

Expertise: Geography Lead

After graduating with a degree in Geography, Bridgette completed a PGCE over 25 years ago. She later gained an MA Learning, Technology and Education from the University of Nottingham focussing on online learning. At a time when the study of geography has never been more important, Bridgette is passionate about creating content which supports students in achieving their potential in geography and builds their confidence.

Jenna Quinn

Author: Jenna Quinn

Expertise: Head of New Subjects

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.