The Hadley Cells

Question 1

How many Hadley cells are there

Answer 1

Two - one in each hemisphere (as with all cells)

Question 2

What do the two Hadley cells form

Answer 2

The basis of tropical air circulation and are responsible for the seasonal changes in climate of those regions that experience a wet and dry climate

Question 3

What are the four components that each Hadley cell can be divided into

Answer 3

• ITCZ
• Coriolis effect
• Subtropical anticyclones
• Trade winds

Question 4

Coriolis effect

Answer 4

At high altitudes the air moves polewards. This usually circulates as upper westerly winds around the planet as a result of the deflection effect of the rotation of the earth (Coriolis effect). Net effect = air still moves polewards

Question 5

Subtropical anticyclones

Answer 5

Around 30•N and S, the colder air at higher altitudes begins to sink, or subside, back to the earths surface. As it descends it warms and any moisture evaporates. At the surface, high pressure is created, with cloudless skies = subtropical anticyclones

Question 6

Inter-tropical convergence zone (ITCZ)

Answer 6

Occurs between the two Hadley cells. Area of low pressure in equatorial latitudes.
Sun here is high in the sky so ground heats rapidly by day and much surface evaporation.
Hot air rises in convection currents = area of low pressure develops
This rising air cools and water vapour condenses, giving heavy rainfall.

Question 7

Trade winds

Answer 7

On reaching the ground, some of the air returns towards equatorial areas as consistent winds known as trade winds. These are subject to coriolis effect.

Question 8

How do the trade winds move

Answer 8

From a northeasterly direction in the northern hemisphere and from the southeast in the Southern Hemisphere. The two trade wind systems move air towards the equator where it forms the ITCZ.