Atmospheric circulation Flashcards
What is the cell model?
The purpose of the cell model is to redistribute surplus energy (heat), from tropical regions to the poles, as well as the cooler air from poles to the equator
High pressure regions
Where air is descending, an area of high pressure forms, giving largely clear skies and little rain as high pressure suppresses weather development
Low pressure regions
Where air is rising, an area of low pressure forms, as air rises it condenses and cools and so areas experience a lot of rainfall
Hadley cell
Intensity of solar energy at equator causes earth’s surface to heat up, and heat the air above the surface. The warm air rises and creates a low pressure area
As the air rises and reaches the tropopause, it splits and spreads along to the north and south
As air moves away from equator, it cools and sinks at around 30º north and south of the equator
Sinking air creates an area of high pressure. The sinking air splits and some travels back to the equator, completing the Hadley cell, and some moves polewards (Ferrel cell)
Cell is thermally driven
Polar Cell
Cold, dense air descends over poles, creating an area of high pressure. The air moves along the surface pf the earth towards the equator as polar easterlies
At around 60º N & S, the air warms and rises again, creating area of low pressure
The ascending air splits, some moves towards pole to continue Polar Cell process, and some enters the Ferrel cell
Polar cell is thermally driven
Ferrel Cell
Thermally indirect cells as they’re dependant on the motion from the other 2 cells
When the air from the Hadley cell that’s headed polewards meets the polar easterlies, it helps to warm the air and causes it to rise
Some air will move poleward to complete the Polar cell, whilst the rest moves towards the equator to complete the Ferrel Cell
Ferrel cell allows for transfer of warm air from Hadley cells (equator) to the poles, whilst moving cold air to the equator to be rewarmed
Coriolis effect
The earth rotates from West to East, so in the Northern Hemisphere the winds are deflected to the right, whilst in the Southern Hemisphere they’re deflected to the left
(This results in jet streams, which are types of air current that form high in the atmosphere and move storms and other weather systems from West to East)
