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.

Outlines

00:00

🌍 Atmospheric Circulation and the Coriolis Effect

This paragraph discusses the global atmospheric circulation, which is divided into three cells per hemisphere: the Hadley, Ferrel, and Polar cells. It explains how the Earth's rotation causes the Coriolis effect, which influences wind patterns, creating jet streams and prevailing winds. The Coriolis effect is due to the Earth's surface moving faster at the equator compared to the poles, causing air to deflect as it moves between these regions. This deflection is crucial for understanding wind patterns around high and low-pressure systems in both hemispheres. The paragraph also describes how the conservation of angular momentum accelerates air away from the equator, leading to the formation of the subtropical jet stream at high altitudes with extremely strong winds. Additionally, it covers the polar front jet, which forms at the boundary between cold polar and warm tropical air, and how temperature contrasts across the polar front affect the jet's strength.

05:01

🛳️ Trade Winds and Jupiter's Atmospheric Circulation

The second paragraph delves into the persistent trade winds formed by the surface flow of the Hadley cells, which are deflected by the Coriolis effect to create the northeast trade winds in the Northern Hemisphere and the southeast trade winds in the Southern Hemisphere. These winds played a significant role in enabling sailing ships to establish trade routes between Europe and America. The paragraph also touches on how the prevailing westerly and southwesterly winds over the UK are a result of the Coriolis effect deflecting southerly winds to the right. Lastly, it draws a comparison to Jupiter, highlighting that the gas giant also has atmospheric circulation cells similar to Earth's, with its rapid rotation and large size intensifying the Coriolis effect and creating multiple bands of rising and falling air, giving Jupiter its characteristic striped appearance.

Keywords

💡Atmospheric Circulation

Atmospheric circulation refers to the large-scale movement of air in the Earth's atmosphere. It is fundamental to understanding weather patterns and climate. In the video, atmospheric circulation is described as being split into three cells in each hemisphere, which is crucial for the formation of wind patterns and climate zones.

💡Hadley Cell

The Hadley Cell is one of the three major cells of atmospheric circulation, characterized by a circulation of air rising near the equator and sinking at about 30 degrees latitude in both hemispheres. It plays a significant role in the formation of trade winds and the subtropical high-pressure belt, as mentioned in the script.

💡Ferrel Cell

The Ferrel Cell is another cell in the global circulation pattern, positioned between the Hadley and Polar Cells. It is characterized by the west-to-east flow of air in the mid-latitudes. The video explains how the rotation of the Earth influences the winds within this cell, contributing to prevailing wind patterns.

💡Polar Cell

The Polar Cell is the cell of atmospheric circulation located near the poles, where air sinks and moves towards the equator at the surface. The script discusses how the Polar Cell interacts with the Ferrel Cell to create the polar front jet stream, which is significant for weather patterns in the mid-latitudes.

💡Coriolis Effect

The Coriolis Effect is the apparent deflection of the path of an object moving in a rotating system. In the context of the video, it is key to understanding how the Earth's rotation influences wind patterns, causing them to curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

💡Angular Momentum

Conservation of angular momentum is a principle that explains why objects in orbit, or moving through the Earth's atmosphere, maintain a constant rate of rotation. The video uses this concept to explain the speeding up of air as it moves away from the equator towards the poles, leading to the formation of jet streams.

💡Jet Stream

A jet stream is a narrow band of strong wind found in the atmosphere. The video describes two types of jet streams: the subtropical jet stream, which is associated with some of the strongest winds on Earth, and the polar front jet stream, which marks the boundary between cold polar air and warm tropical air.

💡Prevailing Winds

Prevailing winds are the dominant wind patterns in a region, influenced by the Earth's rotation and atmospheric circulation. The script explains how the Coriolis Effect and the movement of air within the Hadley and Ferrel Cells result in the trade winds and westerlies experienced around the globe.

💡Trade Winds

Trade winds are steady winds that blow from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere towards the equator. The video script mentions how the Coriolis Effect influences these winds, giving them their westward deflection.

💡Polar Front

The polar front is the boundary between cold polar air and warm tropical air. The video discusses how the polar front jet stream forms at this boundary and is influenced by the temperature contrast across it, with stronger jets occurring in winter due to greater temperature differences.

💡Jupiter

Although not the main focus, the video script briefly compares Earth's atmospheric circulation to that of Jupiter, highlighting the Coriolis Effect's role in creating multiple circulation cells and the striped appearance of the planet due to its rapid rotation.

Highlights

Atmospheric circulation is divided into three cells in each hemisphere: the Hadley cell, Ferrel cell, and polar cell.

The Earth's rotation influences wind patterns, creating jet streams and prevailing winds.

The Coriolis effect is due to the Earth's surface rotating faster at the equator than at the poles.

Air moving away from the equator appears to curve due to the Coriolis effect, without any physical force causing the deflection.

The conservation of angular momentum causes air to speed up as it moves away from the equator towards the poles.

The subtropical jet stream, located between 12 to 15 kilometers high, is associated with some of the strongest winds on Earth.

The polar front jet stream forms at the boundary between cold polar air and warm tropical air, known as the polar front.

The polar front jet stream is stronger in winter due to greater temperature contrasts.

Waves in the jet stream can cause Atlantic depressions to deepen explosively.

Surface winds are deflected by the Coriolis force, forming persistent trade winds in both hemispheres.

The trade winds allowed sailing ships to cross the Atlantic and opened up trade routes between Europe and America.

The prevailing westerly and southwesterly winds experienced over the UK are influenced by the Coriolis effect.

Jupiter also has circulation cells similar to those on Earth, with a much stronger Coriolis effect due to its rapid rotation.

Jupiter's fast rotation and great size result in many circulation cells, producing its distinctive striped appearance.

The Coriolis effect plays a major role in explaining wind patterns around low and high pressure systems in both hemispheres.

The deflection of winds by the Coriolis force is crucial for understanding weather patterns and global circulation.

Transcripts

the last video showed that our

atmospheric circulation is split into

three cells in each hemisphere the

Hadley cell Farrell cell and polar cell

[Music]

in this third video in the global

circulation series we will look at the

winds within these cells and how the

rotation of the earth influences these

winds to give us jet streams and

prevailing wind patterns as well as

being split into three cells the global

circulation pattern is at an angle due

to the Earth's rotation the spin of the

earth induces an apparent motion to the

right in the northern hemisphere and to

the left in the southern hemisphere

this is the Coriolis effect

the key to the Coriolis effect lies in

the fact that the Earth's surface

rotates faster at the equator than at

the poles this is because the earth is

wider at the equator so has further to

travel in one day the result of this

means that as air moves away from the

equator it doesn't move in a straight

line

relative to the Earth's surface instead

it appears to an observer on the ground

to move in a slightly curved direction

but there is no physical force causing

this deflection as the atmosphere

rotates with the earth it is just due to

the air flowing for a region that is

moving faster to a region that is moving

more slowly to explain this further

imagine an air parcel as a ball the ball

is thrown from the equator towards a

point near the North Pole even though it

moves in a straight line the ball will

appear to an observer on the ground to

curve away and land to the right of its

targets as the points near the North

Pole is moving more slowly and is not

caught up if the ball is now thrown from

the North Pole towards a point near the

equator it will again appear to a

surface observer to land to the rights

of its targets but this time is because

the Earth's surface at the equator is

moving faster and has moved ahead of the

ball this effect only happens on objects

that are in motion this deflection is a

major factor in explaining why winds

blow anti-clockwise around low pressure

and clockwise around high pressure in

the northern hemisphere and vice versa

in the southern hemisphere so when

flowing towards the North Pole air is

deflected towards the east and when

traveling southwards back towards the

equator it is deflected westwards

the same overall result occurs in the

southern hemisphere how does this lead

to eastwards flowing jet streams and

prevailing winds as air moves away from

the equator at the top of the Hadley

cells toward higher latitudes it starts

to be deflected by the Coriolis force

just as a skater spins faster by

bringing their arms and legs closer to

their bodies air moving away from the

equator speeds up as it gets closer to

the Earth's spin axis this process is

known as the conservation of angular

momentum the magnitude of the Coriolis

force increases towards the poles so by

the time the air reaches 30 to 40

degrees north or south it is moving in

an eastward direction this subtropical

jet stream occurs high in the atmosphere

between 12 to 15 kilometers it is

associated with some of the strongest

winds on earth reaching over 280 miles

per hour at times as this jet sits

between the descending branches of the

Hadley and Farrell cells there is little

Associated weather the polar front jet

forms in a different way

this jet sits between the rising

branches of the polar and Farrell cells

it marks the boundary between cold polar

air and warm tropical air known as the

polar front the polar front jet occurs

at a height of 11 to 13 kilometers and

is primarily the results of the

temperature contrast across the polar

front the stronger the temperature

contrast across the front

the stronger the Jets so it follows that

the polar front jet is stronger in the

winter than the summer

waves or ripples along the jet stream

can cause Atlantic depressions to deepen

explosively

as they are steered towards the UK winds

at the surface are also subject to

deflection from the Coriolis force the

surface flow of the Hadley cells form

the persistent trade winds as air flows

towards the equator it is deflected

towards the west in both hemispheres

forming the Northeast trade winds in the

Northern Hemisphere and the southeast

trade winds in the southern hemisphere

the persistence of these winds allowed

sailing ships to cross the Atlantic and

opened up trade routes between Europe

and America giving them their name the

surface wind and the feral cells would

flow from a southerly direction in the

northern hemisphere but the Coriolis

effect causes this wind to be deflected

to the right leading to the prevailing

westerly and southwesterly winds often

experienced over the UK this setup is

not unique to our planet

Jupiter also has circulation cells

similar to those on earth a day on

Jupiter lasts for about nine and a half

hours so it is rotating much more

quickly than the earth the great size

and fast rotation of this planet makes

the Coriolis effect very strong this

splits the Jovian atmosphere into many

circulation cells in each hemisphere

producing numerous alternating bands of

rising and falling air in giving Jupiter

a distinctly striped appearance

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