Chapter 8 Objectives:
Geography 12
Worksheet 8.4
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key
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8.4 Climatic Controls: The Global Wind Systems
Read pages 141 – 146 of Planet Earth: A Physical Geography. Answer
the following questions:
Vocabulary (1 mark each)
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Pressure Gradient:
The change in air pressure as one moves from one location on the earth to another.
Subtropical Highs:
The zones of descending air found approximately 30 degrees north and south of the
equator. The wind systems known as the westerlies and the trade winds blow out of the
subtropical high pressure zones.
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Subpolar Lows:
The zones of ascending air found at approximately 60 degrees north and south of the
equator. The wind systems known as the polar easterlies and the westerlies blow into
the subpolar lows.
Jet Streams:
The high altitude winds that flow around the planet in both hemispheres at heights of
between 9 and 12 km. Their path is wavy or meandering in nature and they mark the
division between cold polar air and warm tropical air.
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Understand the relationship
between weather and
climate
Understand important terms
that are associated with the
study of climate
Appreciate the importance
of classifying climatic
conditions in various ways
Recognize that the climatic
patterns on earth are
complex and that they
result from a wide variety
of interacting forces which
include the earth’s basic
motions, the earth’s
surface features, and the
arrangement of the earth’s
land masses and water
bodies
Identify the importance of
the sun in powering climatic
systems
Appreciate that our
understanding of climate
and weather is still
developing and that many
theories have yet to be
proven to be true
Appreciate the extreme
variability and complexity
of the earth’s climates
Examine ways that humans
both influence and are
influenced by climate an
weather
Cyclones:
An area of low atmospheric pressure
Anticyclones:
An area of high atmospheric pressure
Short Answer (2 marks each)
1. Describe in your own words how warm air typically leads to low atmospheric
pressure. Describe in your own words how cold air typically leads to high
atmospheric pressure.
As the air molecules warm, they begin to move and spread out. The air is able to hold more..such as
vapor.
Cold air has more molecules of air per unit, which makes it heavier. Gravity pulls it to the earth. It
weighs more than hot air.
2. What is the relationship between pressure gradient and wind speed. Explain.
Since warm air rises, cold air sweeps in to take its place. Winds blow from cold areas (high pressure)
into warm areas (low pressure) to replace the air that has risen. The higher the difference between high
and low pressure, the stronger the winds are.
3. Briefly explain how the Coriolis Force effects global winds?
Due to the spinning of the earth, the atmospheric winds are deflected to the right in the
Northern Hemisphere and to the left in the Southern Hemisphere
4. Briefly explain what causes subtropical highs.
As the heated air from the equator rising meets the colder air from the poles, the cold air being heavier
rapidly sinks to the earth. The areas of high pressure (heavier, dense air descending to the earth) are
called subtropical highs. They are found approximately at 30 degrees north and south of the equator.
5. Briefly explain what causes subpolar lows.
Some of the air descending at the subtropical high is flows towards the equator (trade winds) and some
flows towards the poles (westerly winds). As the westerlies flow towards the poles, they meet the winds
flowing towards the equator (high pressure zones). When these two surface wind systems meet, the warm
air is forced upward. We call this zone of low pressure the subpolar lows.
6. What is the jet stream and what two ways does it affect our weather? (3 marks)
The jet stream is a high-altitude wind that divides the cold polar air and the warm tropical air. 1. The
waves in the jet stream help develop the low pressure systems and the high pressure systems that
dominate the weather (storms or sunshine). 2. The jet stream also seems to be the process by which
surplus energy in the equatorial regions is moved to the poles.
7. What is the prevailing wind in Golden, BC? Why?
Westerly. We live in the area north of the 30 parallel (50 degrees north) in which the westerlies blow.