Summary of The Atmosphere from the X-Kit Achieve textbook. Covers Earth's energy balance, the movement of air, global air circulation, winds relating to regional and local air movements, Africa's weather and climate, El Niño and La Nina, drought and desertification.
Grade 11 Climate – X-Kit Achieve and Focus
The Atmosphere
Unit 1: Earth’s energy balance
• Energy: the capacity to do work.
• The unequal heating of the atmosphere:
o Insolation/incoming solar radiation heats the surface of the earth.
o Terrestrial radiation is Earth’s heated surface that gives off heat energy, which heats the
atmosphere.
o The amount of solar radiation that reaches Earth’s surface varies according to latitude and
season:
§ More heat at the equator than at the poles.
§ Atmosphere is heated more in summer than winter.
o The movement of air and water masses transfers heat from areas that receive more heat to areas
that receive less heat.
• Latitudinal differences in the heating of the atmosphere:
o The sun’s rays are more direct at the equator and less direct at places further from the equator.
o This means that the same amount of energy is available to heat a smaller surface of the earth and
Earth’s atmosphere at the equator than at the places further from the equator.
o At the poles, the same amount of energy has to heat a larger surface area and larger amount of
atmosphere.
o Places closer to the equator are therefore hotter than places further from the equator.
o The sun is only overheard between the tropic of cancer and tropic of Capricorn.
o The thermal equator moves between the tropic of cancer and Capricorn.
The sun’s rays are more direct at the equator. The rays pass
through a thinner layer of atmosphere at the equator and so less
insolation is lost through scattering, reflection and absorption. At
the equator, the rays also have a smaller area of Earth’s surface
to heat, and there is less atmosphere to be heated by the Earth.
It is for this reason that average temperatures are hotter at
places that are closer to the equator. The opposite happens at
the poles.
1
, Grade 11 Climate – X-Kit Achieve and Focus
• Latitudinal heat zones of Earth:
• Seasonal differences in the heating of the atmosphere:
o Places are hotter in summer because:
§ Places receive more insolation as the sun is more directly overhead.
§ Places experiences more daylight hours so there is more time for insolation to take
place.
o As one moves further from the equator, the difference between summer and winter
temperature increases and the difference between the length of fay and night becomes
greater.
2
, Grade 11 Climate – X-Kit Achieve and Focus
• The effect on energy of Earth’s rotation around its axis and revolution around the sun:
o The tilt of the Earth’s axis:
§ Earth’s ais is an imaginary line extending between the north pole and the south pole.
§ 24 hours to rotate once about its axis.
§ The rotation results on day and night. During one rotation, places that face the sun
experience day and places that face away from the sun experience night.
§ The circle of illumination divides Earth into the parts that are experiencing night and
day.
§ Places receive insolation only during the day.
§ Earth’s axis is tilted at a constant angle of 23.5° to the vertical.
§ Different parts of earth are tilted towards the sun at different times of year.
§ Therefore, areas that are tilted towards the sun experiences longer days and shorter
nights so there is more time for insolation to heat Earth’s surface so these places are
hotter than those tilted away from the sun.
o Revolution of Earth around the sun:
§ Earth moves in an orbit or path around the sun
§ One revolution of earth around the sun takes 365 and a quarter days.
§ Revolution of sun results in seasons.
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