Planetary Winds and Pressure Belts

• Wind is the movement of air across the Earth's surface, flowing from high to low-pressure zones.
• Permanent high and low-pressure zones on Earth's surface create consistent wind patterns.
• Prevailing or planetary winds are those that blow in a permanent pattern.

Planetary Pressure Belts and Prevailing Winds

• Three planetary pressure belts lead to three types of prevailing winds: easterlies, westerlies, and trade winds.
• Pressure belts correlate with typical weather conditions.
• Prevailing winds cause seasonal climate changes.
• Low-pressure areas are linked to high precipitation, which explains why rainforests are near the Equator.
• High-pressure areas are linked to arid climates, explaining the location of most of the world's deserts.

Causes of Global Wind Patterns

• Uneven solar heating, known as differential heating, occurs because the equatorial area receives more heat than the polar areas.
• Warm air rises at the Equator and moves towards the poles, creating the Equatorial Low-Pressure Zone, also known as the Intertropical Convergence Zone (ITCZ).
• Around 30° north and south, the air cools, descends, and forms Subtropical High-Pressure Zones.
• Cold air descends at the poles, forming Polar High-Pressure Zones.
• Cold polar air moves towards the Equator but begins to rise around 60° north and south.
• Permanent air pressure zones result in permanent wind patterns called prevailing winds.
• Three types of prevailing winds exist: polar easterlies, westerlies, and easterlies (trade winds).
• The Coriolis effect deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere due to Earth's rotation.

Atmospheric Circulation Cells

• Hadley cell: Air moves between 0° and 30° north and south, rising at the Equator and sinking at 30°, creating easterlies or trade winds.
• Ferrel cell: Air moves between 30° and 60° north and south, rising at 60° and sinking at 30°, creating westerlies.
• Polar cell: Air moves between 60° and 90° north and south, rising at 60° and sinking at 90°, creating polar easterlies.
• The pattern of high and low pressures and wind movement are the same in both hemispheres.

Types of Wind Belts

• Winds are named based on the direction from which they originate.
• Easterlies originate from the east, while westerlies originate from the west.

Tropical Easterlies

• Tropical easterlies are also known as trade winds.
• They were historically used by traders to sail across the Atlantic Ocean to the "New World".
• These winds blow between 30° north and 30° south latitude towards the Equator.
• In the Northern Hemisphere, they are called north-east trade winds.
• In the Southern Hemisphere, they are called south-east trade winds.
• Trade winds converge at the Equator, forming the Intertropical Convergence Zone (ITCZ).
• The ITCZ is characterized by rising air and very little wind, leading to it being known as the "doldrums".

Prevailing Westerlies

• Westerlies blow between 30° and 60° latitudes (both north and south) towards the poles.
• In the Northern Hemisphere, they are called south westerlies and come from the southwest.
• In the Southern Hemisphere, they are called north westerlies and come from the northwest.
• Ships once used westerlies to return to Europe across the Atlantic Ocean.

Polar Easterlies

• Polar easterlies blow from the polar regions to around 60° north and south.
• They are very cold wind.
• Polar easterlies rise around 60°, creating low-pressure zones called polar fronts.

Explore planetary winds, pressure belts, and their impact on global climate patterns. Learn about easterlies, westerlies, and trade winds, and discover how pressure belts correlate with typical weather conditions, influencing precipitation and seasonal climate changes.