How Earth’s Geography Effects Weather & Climate (College Board AP® Environmental Science): Study Guide

Factors affecting weather & climate

What is the difference between weather and climate?

Weather

• Weather refers to the current state of the atmosphere at a specific time and place

• Weather conditions can change rapidly (e.g. over just a few hours)

• This includes short-term variations in:

  • temperature

  • humidity

  • cloud cover

  • precipitation

  • wind speed

  • air pressure

Climate

• Climate refers to the long-term average of weather conditions in a particular region or location

  • It describes the overall patterns, trends and variations in atmospheric factors (temperature, humidity etc.) over relatively long time periods

    • Climate is the average of these conditions over approximately 30 years or more

  • Climate is influenced by various factors such as solar radiation, atmospheric circulation patterns, ocean currents, land features and greenhouse gas concentrations

• Climate provides a broader perspective on long-term atmospheric behaviour

• Whereas, weather is more concerned with immediate atmospheric conditions and forecasts

• Understanding the difference between climate and weather is crucial for:

  • Analysing long-term climate trends

  • Predicting short-term weather events

  • Assessing the impacts of climate change on weather patterns

Geographic factors influencing weather and climate

• Both weather and climate are influenced by geographic and geologic factors, including mountains, oceans, altitude, and latitude

Latitude

• Distance from the equator determines temperature and seasonal variations

• Tropical regions (near the equator) receive consistent, direct sunlight, leading to warmer climates

• Polar regions receive less direct sunlight, causing colder temperatures

• Example: The Arctic and Antarctic Circles have extreme seasonal variations due to Earth's tilt

Altitude

• Higher altitudes have lower temperatures and thinner air

• Air pressure decreases with height, reducing the ability to retain heat

• Example: Mount Kilimanjaro, located near the equator, has snow at its peak due to high elevation

Proximity to oceans

• Oceans regulate temperatures by absorbing and releasing heat slowly, leading to milder coastal climates

• Coastal areas experience less temperature fluctuation than inland regions

Ocean currents

• Warm and cold ocean currents transport heat, affecting climate in coastal regions

• Gulf Stream (warm current) keeps Europe’s climate milder than expected for its latitude

• California Current (cold current) cools the west coast of North America

Wind patterns

• Global wind belts (such as trade winds and westerlies) distribute heat and moisture across the planet

• Prevailing winds influence precipitation patterns and temperature

• Example: The jet stream affects weather patterns in North America, bringing storms and cold fronts

Continentality (distance from water)

• Inland areas experience more extreme temperatures due to lack of ocean regulation

• Coastal regions have milder temperatures because water retains heat longer than land

• Example: Russia’s interior has harsh winters and hot summers due to its distance from the ocean

Rain shadows

What is a rain shadow?

• A rain shadow is a dry region on the leeward side of a mountain range that receives little precipitation

• Mountains block moist air, forcing it to rise, cool, and release moisture on the windward side before descending dry on the other side

• This process creates distinct wet and dry zones

How rain shadows form

1. Moist air from an ocean or lake moves inland

2. The air rises up the windward side of a mountain, cooling and condensing into precipitation

3. As the air reaches the summit, most moisture has already fallen as rain or snow

4. The now dry air descends on the leeward side, warming and creating arid conditions

Effects of rain shadows

• The leeward side of the mountain becomes dry and desert-like

• The windward side remains lush and receives higher rainfall

• Affects agriculture, ecosystems, and human settlements

Examples of rain shadows

• Sierra Nevada Mountains (USA) → The Great Basin Desert forms on the leeward side

• Andes Mountains (South America) → The Atacama Desert is one of the driest places on Earth

• Himalayas (Asia) → The Tibetan Plateau lies in a rain shadow