Chapter 19 Reading Guide
The Atmosphere in Motion
19.1: Air Pressure and Wind
Elevation
Increasing Elevation leads
to decreasing air pressure
Air Pressure
Temperature
Decreasing temperature
leads to increasing air
pressure
Humidity
Increasing humidity leads to
decreasing air pressure
1. Define air pressure. Then describe the likely weather in both high and low-pressure
conditions.
Air pressure is the weight of the atmosphere pushing on surfaces.
In high-pressure conditions, weather is usually fair, cool, and dry.
In low-pressure conditions, weather is usually cloudy, warm and humid with
precipitation possible.
2. Name and describe a way to measure air pressure.
A mercury barometer uses the height of mercury in a glass column to measure the
surrounding pressure; the greater the pressure, the higher the mercury column rises.
19.2: Factors Affecting Winds
List the ways that the Coriolis effect and friction affect wind.
Coriolis Effect
Pushes winds to their right in the Northern
Hemisphere; to their left in the Southern
Hemisphere
Creates clockwise spiral of winds in a highpressure area
Creates counter-clockwise spiral of winds
in a low-pressure area
Friction
Lessens impact of Coriolis effect, allowing
winds to blow on truer course
Greater effect over flat land than hilly land
Greatest effect over the ocean
Effect on winds decreases with elevation
1. Define the jet stream and explain the effect friction has on it.
The jet stream is a band of fast-moving winds that flow west to east and can encircle the
globe. Because the winds are so high up in the troposphere, friction does not slow the jet
stream down.
19.3: Global Wind Patterns
1.Explain how warm and cool air circulate through the cells of the three-celled circulation
model. Discuss how the Coriolis effect changes the direction of the air as it circulates.
In each cell, warm air circulates toward the poles and cool air circulates toward the
equator. In the Northern Hemisphere, the Coriolis effect pushes the warm air and the
cool air east. In the Southern Hemisphere, this effect is reversed. The circulation
direction alternates from cell to cell.
Global wind patterns create somewhat predictable conditions at different places on Earth.
List the likely conditions in each latitude zone.
Air Temperature
Air Pressure
1. 0 - 30
2. 30- 60
3. 60 - 90
Hottest
Hot
Warm
Low
High
Low
4. 90
Coldest
High
Surface wind
direction and
strength
Least wind; easterly
Little wind, westerly
Steady wind,
easterly
Steady wind,
easterly
19.4 Continental and Local Winds
Under each label, describe the change of direction and temperature of the air as time
passes.
Sea Breeze Circulation
During the day, land heats up more quickly
than water does
Land-Breeze Circulation
At night, land cools more quickly than
water does.
Describe monsoon winds and explain how the effects of both the seasons and the
continents combine to create these winds.
Monsoon winds are prevailing winds that change direction seasonally. They occur
because the temperature difference between land and water causes an air-pressure
difference that leads to prevailing winds. In summer, continents heat up, causing lowpressure and inviting high-pressure air to flow inland from the sea. As the moist sea air
rises in the low-pressure zone, rain falls. In winter, continents cool, causing highpressure to flow away from the dry continent toward the sea, causing dry conditions.