Atmosphere Flashcards
Thermally direct cells
Polar and Hadley
Thermally indirect cell
Ferrel
Describe how the Hadley cell is formed
Warm air rises at the equator creating low pressure. It splits and moves towards the poles. It then cools and sinks at 30’ creating high pressure. Winds move the air back to the equator completely the Hadley cell.
Describe the ferrel cell
It’s located between 30’ and 60’ north. It transfers air between the Hadley and polar cells.
Describe how the polar cell is formed
The cold air sinks at the poles creating high pressure. Polar easterlies move the cold air towards the equator. It meets warm air from the tropics and rises. It then moves back to the poles completing the polar cell.
Describe surface winds
In the northern hemisphere the winds are deflected right in the southern left. This is due to the Coriolis effect and the earths spin.
Describe the global heat budget
100% is emitted from the sun. 20% is absorbed into the atmosphere, 3% by clouds and 17% by dust and water vapour. 5% of energy is scattered by gas. 20% is reflected back by white clouds. The 55% remaining goes towards earth. 50% is then absorbed by dark surfaces and 5% is reflected by white surfaces (albedo effect)
Describe global isolation
The suns energy has further to travel to reach the poles. This means there is a greater chance for reflection to take place. Therefore there is less heat at the poles. Due to the earths curvature the suns energy is more concentrated at the equator. The angle of incidence is greater at the poles than at the equator, so the energy is more spread out. Due to the earths tilt the poles are tilted away from the sun receiving less energy overall, whilst the equator receives energy all year round. At the equator vegetation absorbs energy and at the poles ice reflects energy.
Describe the oceans currents
At the equator water moves westwards due to the Coriolis force and resultant global winds which push the water west due to frictional drag. This is added by intense heating. For example the north equatorial currents. When these currents reach land they deflect north and south. Thus moving warm water from the equator to the poles for example the Gulf Stream. At 30’ N and S of the equator the currents are pulled eastwards as they are caught up by global winds for example the North Atlantic drift. The water is then deflected by land again and some of the cold water is deflected back towards the equator again for example the canary current.
Thus completing a gyre.
How do gyres move
Clockwise in the north. Anticlockwise in the south. They bring warm water to cold areas and cold water to warmed areas. Thus helping to balance out energy due to global isolation. Colder currents are denser so move at lower levels. Warmer currents are nearer the surface.
Describe the tropical continental
Hot and dry
Hot- due to the area of greatest insolation
Dry- cause it travels over land so there is no space to pick up moisture
Low humidity- 10%_17%
Stable air mass
Originates from the Sahara desert and creates the harmattan winds
Describe the tropical maritime
Hot and wet
Hot- area of greatest insolation
Wet- originated over the Atlantic Ocean so picks up a lot of moisture
High humidity- 65%-82%
Is the ITCZ fixed
No it moves with the sun
Describe the seasonal movement of the ITCZ
The ITCZ is furthest south in dec-jan. it migrates north and gets the most north in June. The dec-jan is always warms and wet due to the tropical maritime. The towns at the mar-sep ITCZ will be hot and dry but have same rainfall when the ITCZ passes over. The towns at the June ITCZ will be hot desert areas cause the OTCZ might not reach there.
When the ITCZ brings rainfall it…
Provides water for agriculture
May cause river flooding which would fertilise soils
Water can be collected and stored
Sewers can flood and disease spreads
Tracks become muddy and impassable
Heavy rain can lead to top soil erosion
Heavy rain can cause the leaching of materials
Rain allows for plants to flourish which will provide feed for animals
