What is global circulation? | Part Three | The Coriolis effect & winds
Summary
TLDRThis 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
- π Atmospheric circulation is divided into three cells in each hemisphere: the Hadley cell, Ferrel cell, and polar cell.
- π΅ 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.
- π 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.
- π 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.
- π 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.
- πͺοΈ 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.
- π¬οΈ 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.
- βοΈ 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.
- π‘οΈ 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.
- π³οΈ Surface winds, influenced by the Coriolis effect, form persistent wind patterns like the trade winds, which played a significant role in historical trade routes.
- π 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
π 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.
π³οΈ 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.
Mindmap
Keywords
π‘Atmospheric Circulation
π‘Hadley Cell
π‘Ferrel Cell
π‘Polar Cell
π‘Coriolis Effect
π‘Angular Momentum
π‘Jet Stream
π‘Prevailing Winds
π‘Trade Winds
π‘Polar Front
π‘Jupiter
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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