global atmospheric circulation model

Question 1

what are the four air rules?

Answer 1

1. warm air rises, cold air sinks
2. high pressure is air rising, low pressure is air sinking
3. high pressure brings clear skies, low pressure brings cloudy skies
4. wind always moves from high to low pressure areas

Question 2

how does low air pressure occur?

Answer 2

air is warm, less dense and is ascending from the surface of the earth. this air will cool, condense and form clouds, and eventually precipitation will occur.

Question 3

how does high air pressure occur?

Answer 3

when air is cool, dense and is descending towards the surface of the Earth. no clouds will form, and clear skies will occur.

Question 4

describe the ‘global atmospheric circulation model’:

Answer 4

described as a worldwide system of winds moving heat from the equator to the poles to reach a balance in temperatures.

Question 5

what are surface winds and pressure belts?

Answer 5

• surface winds are large scale movements of air due to differences in pressure.
• these differences in pressure are called pressure belts, and this is because the Sun heats the Earth’s surface unevenly.

Question 6

how does air circulate around the Hadley cell?

Answer 6

• the sun’s energy is more concentrated at the equator.
• this causes the air to be warmer, and rise, as it’s less dense, creating low pressure.
• as the air rises, it cools, condenses, and forms cloud.

(this is why there’s so much rainfall and so many rainforests at the equator, as we’ve created a low pressure belt)

• as the air continues to rise, it reaches the top of the troposphere, it moves north and south of the equator, cooling further
• at 30 degrees north and south of the equator, air begins to sink back to earth, as it’s now cool and dense, creating high pressure belts. HORSE LATITUDES

(these areas have high temperatures and low rainfall, so this is where deserts usually occur).

• air then travels back to the equator, as wind flows from high to low pressure, closing the hadley cell loop. TRADE WINDS

Question 7

how does air circulate around the Ferrel cell?

Answer 7

• warm surface winds from 30 degrees north and south of the equator (WESTERLIES) meet cold air from the poles at 60 degrees north and south.
• as warmer air is less dense, it rises above the cooler air into the atmosphere, creating a low pressure belt. it cools, condenses and forms cloud.
• as the air reaches the top of the troposphere, some of the air travels back to the equator, and some moves towards the Poles.

Question 8

how does air circulate around the Polar cell?

Answer 8

• air from 60 degrees north and south of the equator moves towards the Poles, and as it does this, it cools, becoming denser and sinking back to the Earth’s surface, at 90 degrees north and south of the equator, creating high pressure (very little rain).
• air, once it has sunk back to the Earth’s surface travels back to 60 degrees north and south through surface winds.