The Ferrel And Polar Cells Flashcards
Where does the Ferrel cell occur
Higher latitudes (between 30 degrees and 60 degrees north and 30 degrees and 60 degrees south)
What is the Ferrel cell responsible for
Climate types occurring in the mid latitudes
How are the warm southwesterly winds in the northern hemisphere and the northwesterlies in the Southern Hemisphere formed
Air in the surface is pulled towards the poles
As these winds travel across the oceans they..
Pick up moisture
At 60 degrees N and 60 degrees S
The winds meet cold air which has drifted from the poles. The warmed air from the tropics is lighter than the dense, cold polar air and so it rises as the two air masses meet
What happens as the warmer tropic air and cold polar air mix
The uplift of air causes low pressure at the surface and unstable conditions that follow result in the mid latitudes depressions - characteristically experienced in the cook temperate western maritime (CTWM) climate
What happens when the uplift of air reaches the troposphere
Some of the rising air eventually returns to the tropics as part of the Ferrel cell circulation; some is diverted polewards, as part of the Polar cell
How is high pressure formed
On the surface at the N and S poles, descending air from the Polar cell results in high pressure
In both the northern and Southern Hemispheres..
Winds are pulled from the high pressure poles towards the mid latitude low pressure belt, which occurs at around 60 degrees N and 60 degrees S
What does the earth spinning in its axis cause
The prevailing surface winds to be deflected to the left in the Southern Hemisphere and to the right in the northern hemisphere
What do the deflected prevailing winds cause
Cold air to be transported away from high latitudes and warm air is bought in by the polar cell. This helps to address the energy deficit.
What does the three cell model not allow for
- the influence of depressions/anticyclones
- or high level jet streams in the redistribution of energy
Who was the three cell model refined by
Rossby in 1941 - to take into account what it missed
Winds in the upper atmosphere
Blow around the earth in a westerly directional- pilots found this out while flying
What are rossby waves (4)
- follow a wavy undulating pattern
- travel around the earths upper atmosphere
- occur 4-6 times in each hemisphere
- can stretch from the polar latitudes to the tropical latitudes
How do some people believe the rossby waves are caused
By the upper air flow being forced to divert around the great north - once a wave motion has begun it is perpetuated around the planet
What are jet streams
Bands of extremely fast moving air (up to 250 km h-1) within the upper westerly winds
Size of jet streams
Hundreds of km in width
Vertical thickness of 1000-2000 m
Jet streams found at altitudes of
10,000 m
What are jet streams the product of
A large temperature gradient between two air masses
Two main locations of jet streams
- the polar front jet stream (PFJS)
- the sub tropical jet stream (STJS)
The polar front jet stream (4)
- westerly band of wind
- associated with the meeting place of cold polar and warm tropical air
- above the Atlantic Ocean
- marks the division between the polar and Ferrel cells
What does the polar front jet stream (PFJS) help to explain
The formation of mid-latitude low-pressure weather systems, or depressions
The subtropical jet stream (STJS)
- also generally westerly
- associated with the poleward ends of the Hadley cells
- in summer above west Africa and southern India this jet may become easterly
- ^due to higher temperatures over land than over the more southerly sea areas
