Global Wind Patterns and Pressure Belts

• Wind is air movement across Earth's surface from high to low-pressure zones.
• Permanent high and low-pressure zones cause consistent wind patterns called prevailing or planetary winds.

Planetary Pressure Belts

• Three planetary pressure belts result in three types of prevailing winds: easterlies, westerlies, and trade winds.
• Pressure belts influence weather, and prevailing winds cause seasonal climate changes.
• Low-pressure areas correlate with high precipitation, like the rainforests along the Equator.
• High-pressure areas correlate with arid climates, where most deserts are located.

Causes of Global Wind Patterns

• Uneven solar heating, where the Equator receives more heat than the poles, causes differential heating.
• Warm equatorial air rises and moves towards the poles, creating the Equatorial Low-Pressure Zone, also known as the Intertropical Convergence Zone (ITCZ).
• Air cools and descends around 30° north and south, creating Subtropical High-Pressure Zones.
• Cold air descends at the poles, creating Polar High-Pressure Zones.
• Polar air moves towards the Equator but rises around 60° north and south.
• Earth's rotation deflects winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere; this is called the Coriolis effect.

Atmospheric Circulation Cells

Hadley Cell

• Located between 0° and 30° north and south.
• Air rises at the Equator and sinks at 30° north and south.
• Winds move towards the Equator and are called Easterlies or Trade Winds.

Ferrel Cell

• Located between 30° and 60° north and south.
• Air rises at 60° north and south and sinks at 30° north and south.
• Winds move towards the poles and are called Westerlies.

Polar Cell

• Located between 60° and 90° north and south.
• Air rises at 60° north and south and sinks at 90° north and south.
• Winds move towards the Equator and are called Polar Easterlies.
• High and low-pressure patterns, including wind movement, occur in both hemispheres

Types of Wind Belts

• Three main types of prevailing winds include easterlies, westerlies, and polar easterlies.
• Wind names indicate the direction from which they originate.

Tropical Easterlies

• Also known as trade winds, these were historically used by European traders sailing to the "New World".
• These winds blow between 30° north and south towards the Equator.
• In the Northern Hemisphere, they are called north-east trade winds, and in the Southern Hemisphere, they are called south-east trade winds.
• Trade winds converge at the Equator, forming the Intertropical Convergence Zone (ITCZ), characterized by rising air and little wind. ITCZ is located +/- 5° of the equator
• The ITCZ was known as the "doldrums" due to ships being stranded without wind.

Prevailing Westerlies

• Blow between 30° and 60° latitudes (north and south) towards the poles.
• In the Northern Hemisphere, westerlies come from the southwest and are called south westerlies.
• In the Southern Hemisphere, westerlies come from the northwest and are called north westerlies.
• Ships returning to Europe would catch the westerlies across the Atlantic Ocean.

Polar Easterlies

• Blow from the polar regions to around 60° north and south.
• These cold winds rise around 60°, creating low-pressure zones called polar fronts.

Explore global wind patterns caused by pressure belts. High and low-pressure zones create prevailing winds like easterlies, westerlies, and trade winds. These winds influence weather and contribute to climate changes, affecting precipitation and aridity worldwide.