3.1 Global atmospheric circulation

What you need to know:

How global atmospheric circulation works to affect global weather and climate
Examples of the impacts on the UK, deserts and the equator

Why this matters:

Understanding how the wind and air move around our planet (global atmospheric circulation) is super important. It helps us figure out why the weather does what it does, like why some places are hot and sunny, and others are often wet and windy.

What is global atmospheric circulation?

It involves lots of interconnected circular air movements called cells.
Sinking air creates high pressure, rising air creates low pressure.
Surface winds move from high to low pressure, transferring heat and moisture.
Winds curve due to Earth's rotation, known as the Coriolis effect.
Changes seasonally with the Earth’s tilt and rotation affecting sun position.

How does global circulation affect weather in different parts of the world?

UK Weather:
- Cloudy and wet due to meeting of cold polar and warm subtropical air.
- Surface winds from the southwest bring warm and wet conditions.
Desert Climates:
- Hot and dry because sinking air at around 30° north and south creates high pressure zones, preventing cloud formation.
Equatorial Regions:
- Hot and sweaty due to low pressure as the sun is directly overhead.
- Rising hot, humid air cools and condenses, causing heavy rainfall typical of tropical rainforests.

Common misconceptions (these things are WRONG)

Misconception1: Weather is random and cannot be predicted.
Reality: Weather patterns are influenced by global atmospheric circulation and can be forecasted with reasonable accuracy.
Misconception 2: Deserts are only hot because they are close to the equator.
Reality: Deserts are often located in high-pressure zones around 30° latitude where air sinks, making them dry.
Misconception 3: The UK is wet because it is surrounded by water.
Reality: The UK's wet weather is also a result of global wind patterns bringing moist air from the Atlantic.

Summary

Global atmospheric circulation is a complex system that controls weather patterns.
It involves large-scale movements of air, known as cells, that transport heat and moisture around the planet.
These patterns are influenced by Earth’s rotation and its tilt, which change with the seasons.
The UK’s climate, a desert's dryness, and equatorial rainfall are all results of this circulation system.

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