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Summary Grade 11 IEB Geography - The Atmosphere
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An in-depth summary of the atmosphere for Grade 11 Geography students.
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By: sharonkagan • 3 year ago
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UNEQUAL HEATING OF THE ATMOSPHERE Heated by incoming solar radiation.
Earth transfers heat energy into the atmosphere.
The amount of heat energy depends on insolation.
Insolation is not equal all around the surface.
Amount of insolation depends on latitude and seasons.
Latitude
Insolation is greatest at the equator (0o).
Decreases northwards and southwards
from equator to poles 90oN and 90oS
latitude.
TRANSFER OF ENERGY AND ENERGY BALANCE
Unequal insolation results in warmer water in the oceans at the equator and colder water
near the poles.
Air and water can move, and they can transfer heat energy.
Helps to restore energy balance over earth’s surface.
Ocean Currents
Are either warmer or colder than surround sea.
Warm currents move from equator to poles to transfer heat from tropical zones to
temperate zones.
Cold currents move from polar regions towards equator transfer cold water from polar
regions to temperate zones.
,Winds
Are moving air.
Winds can affect temperature over land and sea.
Winds also restore energy balance over Earth’s surface.
ATMOSPHERIC PRESSURE
Unequal Heating and Global Air Circulation
Sun supplies earth with heat energy.
Temperature hottest at equator and decreases northwards and southwards.
Difference in temperature give rise to difference in atmospheric pressure.
The differences cause air movements (vertically and horizontally).
Form global air circulation.
, World Pressure Belts
Atmospheric Pressure - is the weight of the atmosphere on the surface of the earth.
Temperature of the air influences atmospheric pressure.
When there is high temperature, air expands and rises, and low pressure is formed.
Convergence of air on earth’s surface also leads to low pressure.
When there is low temperature, air contracts and sink, and high pressure is formed.
Descending air moves outwards from a high-pressure area and divergence occurs.
The Tri-Cellular Circulation
The cells associated with vertical air
movements:
The Hadley Cell
The Ferrel Cell
The Polar Cell
The Hadley Cells:
Are between equator and 30oN and
30oS.
Intense heat at the equator causes
rapid uplift of hot moist air resulting
in low pressure at the surface.
Called an equatorial low.
As air rises in EL it cools and reaches
dew point.
Condensation occurs and
cumulonimbus clouds form.
At 10 000m above earth’s surface,
air diverges poleward and subsides
at 30oN and 30oS causing high pressure belts.
Called subtropical high.
Warm air descends so no condensation happens.
Areas of subtropical high usually have warm, dry weather.
Easterly Winds:
Are drawn into equatorial low from the subtropical high-pressure belts (30 oN & 30oS).
Also called tropical easterly winds - located in the tropics.
Are surface winds of the Hadley Cell.
Zone where air converges is called the Intertropical Convergence Zone (ITCZ).
Along ITCZ is often thunderstorms.
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