What is global circulation? | Part Three | The Coriolis effect & winds

Summary

This video explores the global atmospheric circulation, focusing on the Hadley, Ferrel, and Polar cells, and how the Earth's rotation influences wind patterns through the Coriolis effect. It explains how air currents are deflected, creating jet streams and prevailing winds, with the subtropical and polar front jets being particularly significant. The video also touches on the impact of these winds on weather and historical trade routes, and draws a comparison with Jupiter's atmospheric circulation.

Takeaways

• 🌍 Atmospheric circulation is divided into three cells in each hemisphere: the Hadley cell, Ferrel cell, and polar cell.
• 🎵 The script is part of a series on global circulation, focusing on the winds within these cells and their formation due to Earth's rotation.
• 🌀 The Earth's rotation causes the Coriolis effect, which influences wind patterns, making them deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
• 🔄 The Coriolis effect is due to the Earth's surface rotating faster at the equator than at the poles, causing air to move in a curved path relative to the ground.
• 🏀 An analogy is used to explain the Coriolis effect: a ball thrown from the equator towards the North Pole appears to curve to an observer due to the Earth's rotation.
• 🌪️ The deflection caused by the Coriolis effect is a key factor in why winds blow anti-clockwise around low pressure and clockwise around high pressure in the respective hemispheres.
• 🌬️ As air moves away from the equator, it speeds up due to the conservation of angular momentum, leading to the formation of eastward-flowing jet streams.
• ✈️ The subtropical jet stream, located 12 to 15 kilometers high, is associated with some of the strongest winds on Earth, sometimes exceeding 280 miles per hour.
• 🌡️ The polar front jet stream forms at the boundary between cold polar air and warm tropical air, and its strength varies with the temperature contrast, being stronger in winter.
• 🛳️ Surface winds, influenced by the Coriolis effect, form persistent wind patterns like the trade winds, which played a significant role in historical trade routes.
• 🌌 The script concludes by noting that other planets, such as Jupiter, also exhibit circulation cells and atmospheric patterns influenced by their rotation and the Coriolis effect.

Q & A

What are the three atmospheric circulation cells in each hemisphere?

The three atmospheric circulation cells in each hemisphere are the Hadley cell, Ferrel cell, and polar cell.

How does the Earth's rotation affect the global circulation pattern?

The Earth's rotation causes the global circulation pattern to be at an angle, inducing an apparent motion to the right in the northern hemisphere and to the left in the southern hemisphere, known as the Coriolis effect.

Why does the Earth's surface rotate faster at the equator than at the poles?

The Earth's surface rotates faster at the equator than at the poles because the Earth is wider at the equator, thus having further to travel in one day.

What is the Coriolis effect and how does it influence wind patterns?

The Coriolis effect is the apparent deflection of moving objects due to the Earth's rotation. It causes winds to blow anti-clockwise around low pressure and clockwise around high pressure in the northern hemisphere, and vice versa in the southern hemisphere.

How does the conservation of angular momentum affect the movement of air away from the equator?

As air moves away from the equator toward higher latitudes, it speeds up due to the conservation of angular momentum, which is a result of the Earth's spin axis and the faster rotation at the equator.

What are jet streams and how are they formed?

Jet streams are narrow bands of strong wind found in the Earth's atmosphere. They are formed by the deflection of air by the Coriolis force as it moves toward the poles and speeds up, and by the temperature contrast across the polar front.

At what altitude do subtropical jet streams occur and what are their wind speeds?

Subtropical jet streams occur high in the atmosphere, between 12 to 15 kilometers, and are associated with some of the strongest winds on Earth, reaching over 280 miles per hour at times.

What is the polar front jet and how does it differ from the subtropical jet stream?

The polar front jet sits between the rising branches of the polar and Ferrel cells, marking the boundary between cold polar air and warm tropical air. It occurs at a height of 11 to 13 kilometers and is primarily the result of the temperature contrast across the polar front, unlike the subtropical jet stream which is formed by the deflection of air moving away from the equator.

How do the trade winds form and what direction do they blow?

The trade winds form as air flows towards the equator and is deflected towards the west in both hemispheres, resulting in the Northeast trade winds in the Northern Hemisphere and the Southeast trade winds in the Southern Hemisphere.

What is the relationship between the Coriolis effect and the prevailing westerly winds experienced over the UK?

The prevailing westerly winds experienced over the UK are a result of the Coriolis effect deflecting southerly winds to the right, leading to the prevailing westerly and southwesterly winds.

Does the Coriolis effect only occur on Earth?

No, the Coriolis effect is not unique to Earth. Other planets, such as Jupiter, also exhibit circulation cells and the Coriolis effect due to their rotation.