Tri-Cellular Model Of Atmospheric Circulation

Question 1

Outline the ‘Tri-Cellular Model Of Atmospheric Circulation’

Answer 1

1) At equator sun is high in sky causing ground to heat rapidly, causes area of low pressure called ITCZ
2) Hot air at equator rises, rising air cools at dew point resulting in condensation and heavy rainfall
3) At high altitudes air moved polewards due to Coriolis effect
4) 30° N and S colder air begins to sink, causing high pressure creating subtropical anticyclones
5) Air returns to equator due to trade winds
6) Two trade winds converge at ITCZ forming Hadley Cell
7) Ferrell Cell occurs between 30° and 60°, sinking air from Hadley Cell pulled towards poles from southwesterlies and northwesterlies
8) At surface of poles, cool descending air results in high pressure, blown towards equator
9) Warm tropic air forced over cool polar air, uplift causes low pressure forming mid-latitude depression
10) Forms rising limb of Ferrell Cell, some air returns to tropics as Ferrell Cell, others flow towards poles as Polar Cell

Question 2

What is the Coriolis effect?

Answer 2

• Deflection of wind due to rotation of the Earth on it’s axis
• Causes deflection of wind to right in northern hemisphere and left in southern hemisphere

Question 3

What is the intertropical convergence zone?

Answer 3

Area of low pressure in equatorial latitudes

Question 4

What does the intertropical convergence zone cause?

Answer 4

Area of precipitation

Question 5

How does the intertropical convergence zone change throughout the year?

Answer 5

• Follows movement of Sun
• May to August: ITCZ heats land surface of sub-continent
• Moves north and south of equator