Embedded Files
What you should know by the end of this lesson:
What you should know by the end of this lesson:
What the Tri-Cell model is
Hadley Cell
Ferrel Cell
Polar Cells
How the Tri-Cell model transfers energy from the equator to the poles
Revision: What is Air Pressure?
Revision: What is Air Pressure?
Air pressure is the force exerted on the ground by the air above it.
Pressure on the Earth’s surface is never constant and is always changing, getting higher and then becoming lower.
Low Pressure
Low Pressure
Low pressure occurs when warm air rises from the Earth’s surface. As air rises, pressure on the Earth’s surface becomes less and the pressure becomes lower.
High Pressure
High Pressure
High pressure is caused when cold air sinks towards the Earth’s Surface. As the air falls, pressure on the Earth’s Surface increases and the pressure becomes higher.
Low and high-pressure zones beside each other want to normalise. At the earth's surface Low- pressure zones draw in the excess moving air along the surface. This creates wind.
High in the atmosphere, the opposite occurs, with air moving from low-pressure zones into a high-pressure zone. This also generates wind.
This circulation from high to low-pressure zones and low to high-pressure zones is known as a Circulation Cell
The 3 Cell Model
The 3 Cell Model
Digital Workbook and Paper Jotter
Write down the definitions of convergence and divergence.
Create a copy of the 3-Cell Model Diagram.
Annotate it with what is actually occurring at each diagram to move air from one area to another.
Add to your diagram the extra information about the Coriolis effect and the effect of trade winds on the 3-cell model.
Convergence: where the air is coming together from opposite directions towards low-pressure areas such as the equator.
Divergence: where the air is moving apart in opposite directions from areas of relatively high-pressure such as in the upper atmosphere in temperate latitudes.
3. Cold air, due to a lack of solar insolation, descends at the poles and travels south to around 60o North.
4. When it is far enough south it begins to warm and rise, returning to the poles at high levels. This creates the Polar Cell (the smallest cell).
5. Between 60o North and 30o North. There is the third cell, the Ferrel Cell. This is driven by friction, not by temperature, and acts as a gear between the Hadley and Polar Cells
2. Some of this air returns as surface NE or SE Trade winds to the Equator to form the Hadley Cell.
1. Warm air rises at the Equator due to the overabundance of solar insolation. It travels in the atmosphere to about 30 degrees north and south cools and sinks.
6. It is in this way that warm air from the Equator is distributed to higher (and cooler) latitudes and cold air from the Poles distributed to lower and warmer latitudes.
Extra
Extra
On the launch page next to lesson 4, you will find a printout and instructions to make a 3D model of the Atmospheric Circulation System
Trade Winds
Trade Winds
Trade Winds
Trade Winds
Air moves from areas of High Pressure to areas of Low Pressure as surface winds.
Because the Earth spins, the winds are deflected. This is called the Coriolis Effect.
In the Northern hemisphere, winds are deflected to the right.
In the Southern hemisphere, winds are deflected to the left.
Trade winds and jet streams moving eastwards in the Northern Hemisphere deforms any Ferrel Cell out of recognition. This is why it was the last of the 3 to be discovered.
Check your Learning
Check your Learning
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