Global atmospheric circulation

• There's an overall movement of air between the equator and the poles that affects the Earth's climate.
• Air Circulates between High and Low Pressure Belts as Surface Winds
• 1. Global atmospheric circulation is the transfer of heat from the equator to the poles by the movement of air.
• 2. Air moves due to differences in air pressure — winds blow from high pressure areas to low pressure areas.
• 3. The global atmospheric circulation system is divided into loops (called cells) — each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt.
• 4. Each hemisphere has three cells. Here's how air moves in these cells:
• * The sun warms the Earth at the equator, causing the air to rise.
• This creates a low pressure belt.
• * As the air rises it cools and moves away from the equator.
• * 30° north and south of the equator, the cool air sinks, creating a high pressure belt.
• * At the ground surface, the
• Westerlies cool air moves either back to the equator (as trade winds) or towards the poles (as westerlies). These winds curve because of the Earth's rotation — this is called the Coriolis effect.
• * 60° north and south of the equator the warmer surface winds meet colder air from the poles. The warmer air rises, creating low pressure.
• * Some of the air moves back towards the equator, and the rest moves towards the poles.
• * At the poles the cool air sinks, creating high pressure. The high pressure air is then drawn back towards the equator.
• Global Atmospheric Circulation Affects Weather Around The World
• Global atmospheric circulation influences weather and climate. For example:
• 1. At the equator, the sun is directly overhead — this means the Earth's surface receives a lot of solar radiation, so it's hot. Warm, moist air rises and forms clouds, so it rains a lot.
• 2. By the time air reaches 30° north and south of the equator, it has released most of its moisture as rain.
• The dry air means there are few clouds and little rainfall, so deserts are often found at this latitude.
• 3. The UK lies close to the low pressure zone at 60° north. Warm rising air brings lots of cloud cover and rainfall, often as low pressure systems carried from the Atlantic by westerly winds.
• Pressure belts and surface winds are determined by global circulation
• Air moves in loops (called cells) from the equator to the poles and back. This gives us surface winds and creates belts of high and low pressure that affect the climate - they're why deserts are so dry and rainforests are so wet.