Atmosphere

Question 1

global heat budget

Answer 1

• 100% insolation
• 20% absorbed by atmosphere (17% gases, dust, water vapour; 3% dark clouds)
• 20% relfected by white clouds
• 5% scattered by dust, gases etc.
• 55% reaches earth’s surface (50% absorbed, 5% reflected)

Question 2

insolation

Answer 2

solar radiation received in the earth’s atmosphere or at its surface

Question 3

global insolation

why is it warmer at equator than at the poles?

Answer 3

• suns energy travels through more atmosphere at the poles meaning there is more chance for reflection or absorbtion to take place
• due to the curvature of the earth, sun’s energy is more concentrated at the equator as the same quantity of energy is spread over over a wider surface area at the poles
• angle of incidence is greater at the poles so energy is more spread out
• due to the tilt of the earth the poles spend part of the year tilted away from the sun and receive less energy; in the tropics the sun is always overhead all year round
• at the equator there is green vegetation which absorbs heat energy whereas the poles are covered in ice and snow which reflects the energy

Question 4

ferrel’s three cell model

what are the three cells?

Answer 4

• hadley (thermally direct)
• ferrel (thermally indirect)
• polar (thermally direct)

Question 5

hadley cell

three cell model

Answer 5

• warm air rises at the equator creating an area of low pressure
• as the air rises it cools and splits north and south
• as the air moves away from the equator it further cools and sinks back down to earth at 30˚ N and S creating an area of high pressure at the surface
• air then moves from high pressure to low pressure back to the equator to complete the hadley cell

thermally direct

Question 6

ferrel cell

three cell model

Answer 6

• at 60˚ N and S, warm air from the equator is forced up and over cooler air from the poles creating an area of low pressure at surface
• as the air rises it cools and splits
• air which moves towards the equator completes the ferrel cell

Question 7

polar cell

three cell model

Answer 7

• warm air which rises at 60˚ N and S, cools and splits, and the air travelling towards the poles further cools and sinks at 90˚ N and S to create an area of high pressure
• air flows from high pressure at 90˚ to low pressure at 60˚ to complete the polar cell

Question 8

global surface winds

atmospheric circulation

Answer 8

• the three-cell model sets up a pattern of global surface winds as air flows from high to low pressure
• due to the earths rotation and the coriolis force, these winds are deflected to the right in the northern hemisphere and to the left in the southern hemisphere known as trade winds

Question 9

ocean currents

atlantic ocean

Answer 9

• ocean currents move in large loops called gyres - in the northern hemisphere they move clockwise due to the coriolus effect
• warm water travels towards the poles e.g. gulf stream, and cold water travels towards the equator e.g. canary current - this is due to differrntial heating and salinity causing warm water to rise to the surface to be moved polewards by surface winds forcing the colder water to move below it towards the equator
• ocean currents are impacted by surface winds which cause frictional drag
• land masses divert ocean currents

Question 10

tropical maritime

characteristics

Answer 10

• hot due to greatest insolation at equator
• wet as it originates over ocean so picks up lots of moisture (rain)
• high humidity (65-82%)
• unstable air mass
• origin is the gulf of guinea (atlantic ocean)

Question 11

tropical continental

characteristics

Answer 11

• hot due to greatest insolation at equator
• dry as it has come over land so there is no moisture to pick up
• low humidity (10-17%)
• stable air mass
• origin is over the sahara desert which creates harmattan winds