tri-cellular model

Question 1

what 3 cells control the circulation of air

Answer 1

polar
ferrel
Hadley

Question 2

what do these 3 cells do

Answer 2

control the circulation of air.
they provide a mechanism for the horizontal exchange of energy from the tropics surplus to mid and high latitudes
they cells are confined vertically to the troposphere - 16km at equator, 6k deep at pools

Question 3

development of the Hadley cell

Answer 3

• the earth’s atmosphere gets its energy from direct solar heating at the equator
• heat is transferred to the air above it and it rises and cools
• RISING AIR MEANS LOW PRESSURE
• here, at the equator where winds (trade winds) meet travelling from high pressure (30°N/S) to low pressure (0°) is known as the inter-tropical convergence zone)

Question 4

what does the inter-tropical convergence zone do

Answer 4

at the equator where winds (trade winds) meet when travelling from high pressure to low pressure

Question 5

what does rising air in the Hadley cell do

Answer 5

• it diverges towards the poles once it reaches the troposphere and sinks again around 30°N/S of the equator
• this air warms producing high pressure
• some air diverts back to the equator (trade winds) and some air moves towards the mid-latitudes to redress the global heat imbalance

Question 6

development of the polar cell

Answer 6

• the very cold conditions over both polar regions leads to subsiding air, producing consistent high pressure at the surface
• from this surface, winds move into mid-latitudes, where air rises at the polar front, returning poleward to complete the cycle

Question 7

development of the ferrel cell

Answer 7

this cell is formed in the mid-latitudes and links the other two cells
- here some of the air from the Hadley cell (30°N/S) moves across the surface as the westerlies towards the mid-latitudes
- at 60°N/S, this warmer air meets the colder air from the polar regions
- this forms the polar front
- here warm air rises and there is low pressure at the surface
- this produces the wet weather associated with depressions

Question 8

global distribution of rainfall

Answer 8

at a global scare, annual rainfall totals can be linked to the pressure belt and wind surface patterns shown in a tri-cellular model
low pressure zones, including the equator have higher rainfall totals (>1500mm), while high pressure regions are associated with low rainfall and arid conditions (<250mm)

Question 9

jet stream definition

Answer 9

is a current of strong wind between 7-15km above sea level. winds move west to east at around 200mph

Question 10

the polar jet stream

Answer 10

(60°N/S) is the strongest. it can cause a steady stream of depressions of the UK, or it can move to the north or south of the US. the jet stream moves in waves called ROSSBY WAVES, which happen because of the friction of the air over the Rocky Mountains

Question 11

upper westerlies

Answer 11

prevailing winds which move east to west between 30° and 60° from the equator. they move from HP to LP and form part of the ferrel cell