3.1 Global Atmospheric Circulation

Question 1

Global atmospheric circulation def

Answer 1

The worldwide system of winds, which transports heat from tropical to polar latitudes. In each hemisphere, air also circulates through the entire depth of the troposphere which extends up to 15km

Question 2

What is the influence of latitude on global atmospheric circulation?

Answer 2

• when Sun’s rays strike the Earth, they are concentrated differently on areas of land depending on the latitude
• at the Equator the Sun’s rays are concentrated (higher insolation) so it is much hotter
• at the Poles the rays are more spread out (lower insolation)

Question 3

What happens when the air at the Equator is heated strongly?

Answer 3

• it rises in low-pressure conditions
• air flows towards the north and south poles
• as warm air rises it cools and condenses
• low pressure brings cloud and rain

Question 4

What happens when the air is at 30 degrees north and south?

Answer 4

• the air sinks under high pressure
• high pressure weather brings dry and clear skies
• this forms a convection cell known as the Hadley Cell

Question 5

What happens to air at the polar latitudes?

Answer 5

• it is colder and denser so it sinks under high-pressure conditions
• air flows towards the Equator
• the air warms as it reaches 60 degrees and rises again under low-pressure conditions
• this forms the Polar Cells

Question 6

Name the cells from north to south

Answer 6

Polar Cell
Ferrel Cell
Hadley Cell
Hadley Cell
Ferrel Cell
Polar Cell

Question 7

Insolation def

Answer 7

The amount of solar radiation (sunlight) an area receives over a specified period of time

Question 8

Convection cell def

Answer 8

When differences in air temperature lead to the formation of areas of high and low air pressure; they become linked by flows of warmer and cooler air

Question 9

Latitude def

Answer 9

A line drawn from west to east on a map showing where places lie relative to the Equator and poles

Question 10

Why does global circulation involve three cells?

Answer 10

• Because the Earth rotates on its axis, generating strong, high altitude winds
• these wrap around the planet like belts
• these winds flow towards the east as the earth spins and interact with convection cells
• these strong winds are known as jet streams

Question 11

Jet streams def

Answer 11

A fast flowing (200 km/hr) current of air that circles the planet at a height of 10 km

Question 12

How does precipitation influence global pressure and surface wind patterns?

Answer 12

• rainfall is high and constant throughout the year at the Equator
• as air rises, it cools slightly
• water vapour is converted into droplets of rain

Question 13

What is the low pressure zone around the Equator called?

Answer 13

the intertropical convergence zone (ITCZ)

Question 14

How does the ITCZ cause tropical storms?

Answer 14

• air rises and it triggers a burst of torrential rain
• sometimes, the ITCZ grows a ‘wave’ of low pressure which extends further than usual
• tropical storms form along these waves
• once they gain energy, they can travel even further away from the Equator

Question 15

Why is rainfall higher in coastal areas in Western Europe?

Answer 15

due to the movement of the Polar jet stream, often bringing stormy conditions to the UK’s west coast

Question 16

Why is rainfall lower around the Tropics of Capricorn and Cancer?

Answer 16

dry air descends as part of the Hadley cell, resulting in arid (dry) conditions

Question 17

Why is precipitation low in the polar regions?

Answer 17

Falls mostly as snow, as cold air cannot hold much water vapour