Transcript Air Masses Chapter 24

Chapter 24
Weather
Table of Contents
Section 1 Air Masses
Section 2 Fronts
Section 3 Weather Instruments
Section 4 Forecasting the Weather
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Chapter 24
Section 1 Air Masses
Objectives
• Explain how an air mass forms.
• List the four main types of air masses.
• Describe how air masses affect the weather of North
America.
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Chapter 24
Section 1 Air Masses
Air Masses
• Differences in air pressure are caused by unequal
heating of Earth’s surface.
• The region along the equator receives more solar
energy than the regions at the poles do.
• Conversely, cold air near the pole sinks and creates
high-pressure centers.
• Differences in air pressure at different locations on
Earth create wind patterns.
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Chapter 24
Section 1 Air Masses
How Air Moves
• Air moves from areas of high pressure to areas of low
pressure. Therefore, there is a general, worldwide
movement of surface air from the poles toward the
equator.
• Temperature and pressure differences on Earth’s
surface create three wind belts in the Northern
Hemisphere and three wind belts in the Southern
Hemisphere.
• The Coriolis effect, which occurs when winds are
deflected by Earth’s rotation, also influences wind
patterns.
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Chapter 24
Section 1 Air Masses
Formation of Air Masses
air mass a large body of air throughout which
temperature and moisture content are similar
• When air pressure differences are small, air remains
relatively stationary.
• If air remains stationary or moves slowly over a
uniform region, the air takes on characteristic
temperature and humidity of that region.
• Air masses that form over frozen polar regions are
very cold and dry. Air masses that form over tropical
oceans are warm and moist.
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Chapter 24
Section 1 Air Masses
Types of Air Masses
• Air masses are classified according to their source
regions.
• The source regions for cold air masses are polar
areas. The source regions for warm air masses
are tropical areas.
• Air masses that form over the ocean are called
maritime. Air masses that form over land are
called continental.
• The combination of tropical or polar air and
continental or maritime air results in air masses
that have distinct characteristics.
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Section 1 Air Masses
Types of Air Masses, continued
Continental Air Masses
• There are two types of continental air masses:
continental polar (cP) and continental tropical (cT).
• Continental polar air masses are cold and dry.
Continental tropical air masses are warm and dry.
• An air mass may remain over its source region for
days or weeks. However, the air mass will eventually
move into other regions because of global wind
patterns.
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Chapter 24
Section 1 Air Masses
Types of Air Masses, continued
Maritime Air Masses
• When these very moist masses of air travel to a new
location, they commonly bring more precipitation and
fog.
• The two different maritime air masses are maritime
polar (mP) and maritime tropical (mT).
• Maritime polar air masses are moist and cold.
Maritime tropical air masses are moist and warm.
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Chapter 24
Section 1 Air Masses
Types of Air Masses, continued
The diagram below shows the four types of air mass that influence North
America.
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Chapter 24
Section 1 Air Masses
North American Air Mass
• The four types of air masses that affect the weather
of North America come from six regions.
• An air mass usually brings the weather of its source
region, but an air mass may change as it moves
away from its source region.
• For example, cold, dry air may become warm and
more moist as it moves from land to the warm ocean.
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Chapter 24
Section 1 Air Masses
North American Air Mass, continued
Tropical Air Mass
• Continental tropical air masses form over the deserts
of the Southwestern United States.
• These air masses bring dry, hot weather in the
summer. They do not form in the winter.
• Maritime tropical air masses form over the warm
water of the tropical Atlantic Oceans.
• Maritime tropical air masses also form over the
warm areas of the Pacific Oceans.
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Chapter 24
Section 1 Air Masses
Reading Check
Which air mass brings dry, hot weather in the summer?
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Chapter 24
Section 1 Air Masses
Reading Check
Which air mass brings dry, hot weather in the summer?
a continental tropical air mass
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Chapter 24
Section 1 Air Masses
North American Air Mass, continued
Polar Air Masses
• Polar air masses from three regions—northern
Canada and the northern Pacific and Atlantic
Oceans—influence weather in North America.
• In summer, the air masses usually bring cool, dry
weather.
• In winter, they bring very cold weather to the northern
United States.
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Chapter 24
Section 1 Air Masses
North American Air Mass, continued
Polar Air Masses, continued
• Maritime polar air masses form over the North Pacific
Ocean and are very moist, but they are not as cold as
continental polar Canadian air masses.
• In winter, these maritime polar Pacific air masses
bring rain and snow to the Pacific Coast.
• In summer, they bring cool, often foggy weather.
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Chapter 24
Section 1 Air Masses
North American Air Mass, continued
Polar Air Masses, continued
• Maritime polar Atlantic air masses move generally
eastward toward Europe. But they sometimes move
westward over New England and eastern Canada.
• In winter, they can bring cold, cloudy weather and
snow.
• In summer, these air masses can produce cool
weather, low clouds, and fog.
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Chapter 24
Section 1 Air Masses
Air Masses
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Chapter 24
Section 2 Fronts
Objectives
• Compare the characteristic weather patterns of cold
fronts with those of warm fronts.
• Describe how a midlatitude cyclone forms.
• Describe the development of hurricanes,
thunderstorms, and tornadoes.
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Chapter 24
Section 2 Fronts
Fronts
• A cool air mass is dense and does not mix with the
less-dense air of a warm air mass.
• Thus, a boundary, called a front, forms between air
masses.
• Changes in middle-latitude weather usually take
place along the various types of fronts.
• Fronts do not exist in the Tropics because no air
masses that have significant temperature differences
exist there.
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Chapter 24
Section 2 Fronts
Fronts, continued
Cold Fronts
cold front the front edge of a moving mass of cold air
that pushes beneath a warmer air mass like a wedge
• If the warm air is moist, clouds will form.
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Section 2 Fronts
Fronts, continued
Cold Fronts, continued
• Large cumulus and cumulonimbus clouds typically
form along fast-moving cold fronts.
• A long line of heavy thunderstorms, called a squall
line, may occur in the warm, moist air just ahead of a
fast-moving cold front.
• A slow-moving cloud front typically produces weaker
storms and lighter precipitation than a fast-moving
cold front does.
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Section 2 Fronts
Fronts, continued
Warm Fronts
warm front the front edge of advancing warm air mass
that replaces colder air with warmer air
• The slope of a warm front is gradual.
• Because of this gentle slope, clouds may extend far
ahead of the surface location, or base, of the front.
• A warm front generally produces precipitation over a
large area and may cause violent weather.
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Section 2 Fronts
Fronts, continued
Stationary and Occluded Fronts
stationary front a front of air masses that moves either
very slowly or not at all
occluded front a front that forms when a cold air mass
overtakes a warm air mass and lifts the warm air
mass of the ground and over another air mass
• Sometimes, when air masses meet, the cold moves
parallel to the front, and neither air mass is displaced.
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Chapter 24
Section 2 Fronts
Polar Fronts and Midlatitudes Cyclones
• Over each of Earth’s polar regions is a dome of cold
air that may extend as far as 60° latitude.
• The boundary where this cold polar air meets the
tropical air mass of the middle latitudes, especially
over the ocean, is called the polar front.
• Waves commonly develop along the polar front.
• A waves is a bend that forms in a cold front or
stationary front.
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Chapter 24
Section 2 Fronts
Polar Fronts and Midlatitudes Cyclones,
continued
midlatitude cyclone an area of low pressure that is
characterized by rotating wind that moves toward the
rising air of the central low-pressure region
• Waves are the beginnings of low-pressure storm
centers called midlatitude cyclones or wave cyclones.
• These cyclones strongly influence weather patterns
in the middle latitudes.
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Section 2 Fronts
Polar Fronts and Midlatitudes Cyclones,
continued
Stages of a Midlatitude Cyclones
• A midlatitude cyclone usually last several days.
• In North America, midlatitude cyclones generally
travel about 45 km/h in an easterly direction as they
spin counterclockwise.
• They follow several storm tracks, or routes, as they
move from the Pacific coast to the Atlantic coast.
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Section 2 Fronts
Polar Fronts and Midlatitudes Cyclones,
continued
The diagram below shows the different stages of a midlatitude cyclone.
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Chapter 24
Section 2 Fronts
Polar Fronts and Midlatitudes Cyclones,
continued
Anticyclones
• Unlike the air in the midlatitude cyclone, the air of an
anticyclone sinks and flows outward from a center of
high pressure.
• Because of the Coriolis effect, the circulation of air
around an anticyclone is clockwise in the Northern
Hemisphere.
• Anticyclones bring dry weather, because their
sinking air does not promote cloud formation.
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Chapter 24
Section 2 Fronts
Reading Check
How is the air of an anticyclone different from that of a
midlatitude cyclone?
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Chapter 24
Section 2 Fronts
Reading Check
How is the air of an anticyclone different from that of a
midlatitude cyclone?
The air of an anticyclone sinks and flows outward from
a center of high pressure. The air of a midlatitude
cyclone rotates toward the rising air of a central, lowpressure region.
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Chapter 24
Section 2 Fronts
Severe Weather
Thunderstorms
thunderstorm a usually brief, heavy storm that consists
of rain, strong winds, lightning, and thunder
• Thunderstorms develop in three distinct stages.
• The thunderstorm dissipates as the supply of water
vapor decrease.
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Section 2 Fronts
Severe Weather, continued
Lightning
• During a thunderstorm, clouds discharge electricity in
the form of lightning.
• The released electricity heats the air, and the air
rapidly expands and produces a loud noise known as
thunder.
• For lightning to occur, the clouds must have areas
that carry distinct electrical charges.
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Section 2 Fronts
Severe Weather, continued
Hurricanes
hurricane a severe storm that develops over tropical
oceans and whose strong winds of more than 120
km/h spiral in toward the intensely low-pressure
storm center
• A hurricane begins when warm, moist air over the
ocean rises rapidly.
• When moisture in the rising warm air condenses, a
large amount of energy in the from of latent heat is
released. This heat increase the force of the rising
air.
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Chapter 24
Section 2 Fronts
Severe Weather, continued
Hurricanes, continued
• A fully developed hurricane consists of a series of
thick cumulonimbus cloud bands that spiral upward
around the center of the storm.
• The most dangerous aspect of a hurricane is a rising
sea level and large waves, called a storm surge.
• Every hurricane is categorized on the Safir-Simpson
scale by using several factors. These factors include
central pressure, wind speed, and storm surge.
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Chapter 24
Section 2 Fronts
Reading Check
Where do hurricanes develop?
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Chapter 24
Section 2 Fronts
Reading Check
Where do hurricanes develop?
over warm tropical seas
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Section 2 Fronts
Severe Weather, continued
Tornadoes
tornado a destructive, rotating column of air that has
very high wind speeds and that maybe visible as a
funnel-shaped cloud
• The smallest, most violent, and shortest-lived severe
storm is a tornado.
• A tornado forms when a thunderstorm meets highaltitude horizontal winds. These winds cause the
rising air in the thunderstorm to rotate.
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Section 2 Fronts
Severe Weather, continued
Tornadoes, continued
• A storm cloud may develop a narrow, funnel-shaped
rapidly spinning extension that reaches downward
and may or may not touch the ground.
• If the funnel does touch the ground, it generally
moves in a wandering, haphazard path.
• The destructive power of a tornado is due to mainly
the speed of the winds. These winds may reach
speeds of more than 400 km/h.
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Chapter 24
Section 2 Fronts
Types of Fronts
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Chapter 24
Section 3 Weather Instruments
Objectives
• Identify four instruments that measure loweratmospheric weather conditions.
• Describe how scientists measure conditions in the
upper atmosphere.
• Explain how computers help scientists understand
weather.
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Chapter 24
Section 3 Weather Instruments
Measuring Lower-Atmospheric Conditions
Air Temperature
thermometer an instrument that measures and
indicates temperature
• A common type of thermometer uses a liquid—
usually mercury or alcohol—sealed in a glass tube to
indicate temperature.
• A rise in temperature causes the liquid to expand and
fill more of the tube. A drop in temperature causes
the liquid to contract and fill less of the tube.
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Chapter 24
Section 3 Weather Instruments
Measuring Lower-Atmospheric Conditions,
continued
Air Temperature, continued
• Another type of thermometer is an electrical
thermometer.
• As the temperature rises, the electric current that
flows through the material of the electrical
thermometer increases and is translated into
temperature readings.
• A thermistor, or thermal resistor, is a type of electrical
thermometer that responds very quickly to
temperature changes.
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Chapter 24
Section 3 Weather Instruments
Measuring Lower-Atmospheric Conditions,
continued
Air Pressure
barometer an instrument that measures atmospheric
pressure
• Changes in air pressure affect air masses.
• The approach of a front is usually indicated by a drop
in air pressure.
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Chapter 24
Section 3 Weather Instruments
Measuring Lower-Atmospheric Conditions,
continued
Wind Speed
anemometer an instrument used to measure wind
speed
• A typical anemometer consists of small cups that are
attached by spokes to a shaft that rotates freely.
• The wind pushes against the cup and causes them to
rotate. This rotation triggers an electrical signal that
registers the wind speed in meters per second or in
miles per hour.
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Section 3 Weather Instruments
Measuring Lower-Atmospheric Conditions,
continued
Wind Direction
wind vane an instrument used to determine direction of
the wind
• The wind vane is commonly an arrow-shaped device
that turns freely on a pole as the tail catches the wind.
• Wind direction may be described by using one of 16
compass directions, such as north-northeast. Wind
direction also may be recorded in degrees by moving
clockwise and beginning with 0° at the north.
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Chapter 24
Section 3 Weather Instruments
Reading Check
Which instrument is used to measure air pressure?
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Chapter 24
Section 3 Weather Instruments
Reading Check
Which instrument is used to measure air pressure?
A barometer is used to measure atmospheric pressure.
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Chapter 24
Section 3 Weather Instruments
Measuring Upper-Atmospheric Conditions
Radiosonde
radiosonde a package of instruments that is carried
aloft by balloons to measure upper atmospheric
conditions, including temperature, dew point, and
wind velocity
• The radiosonde sends measurements as radio waves
to a receiver that records the information.
• When the balloon reaches a very high altitude, the
balloon expands and bursts, and the radiosonde
parachutes back to Earth.
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Section 3 Weather Instruments
Measuring Upper-Atmospheric Conditions,
continued
Radar
radar radio detection and ranging, a system that uses
reflected radio waves to determine the velocity and
location of objects
• For example, large particles of water in the
atmosphere reflect radar pulses.
• The newest Doppler radar can indicate the precise
location, movement,and extent of a storm. It can also
indicate the intensity of precipitation and wind
patterns within a storm.
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Section 3 Weather Instruments
Measuring Upper-Atmospheric Conditions,
continued
Weather Satellites
• Satellite images provide weather information for
regions where observations cannot be made from
ground.
• The direction and speed of the wind at the level of the
clouds can also be measured by examining a
continuous sequence of cloud images.
• Satellite instruments can also measure marine
conditions.
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Section 3 Weather Instruments
Measuring Upper-Atmospheric Conditions,
continued
Computers
• Before computers were available, solving the
mathematical equations that describe the behavior of
the atmosphere was very difficult, and sometimes
impossible.
• In addition to solving many of these equations,
computers can store weather data from around the
world. These data can provide information that is
useful in forecasting weather changes.
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Chapter 24
Section 4 Forecasting the Weather
Objectives
• Explain how weather stations communicate weather
data.
• Explain how a weather map is created.
• Explain how computer models help meteorologists
forecast weather.
• List three types of weather that meteorologists have
attempted to control.
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Chapter 24
Section 4 Forecasting the Weather
Global Weather Monitoring
• Weather stations around the world exchange the
weather information they have collected.
• The World Meteorological Organization (WMO)
sponsors a program called World Weather Watch to
promote the rapid exchange of weather information.
• It also offers advice on the effect of weather on
natural resource and on human activities, such as
farming and transportation.
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Interactive weather map
• http://www.wunderground.com/wundermap/
http://www.edheads.org/activities/wea
ther/
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Chapter 24
Section 4 Forecasting the Weather
Weather Maps
Weather Symbols
station model a pattern of meteorological symbols that
represent the weather at a particular observing
station and that is recorded on a weather map
• Common weather symbols describe cloud cover,
wind speed, wind direction, and weather conditions,
such as type of precipitation and storm activity.
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Section 4 Forecasting the Weather
Weather Maps, continued
Weather Symbols, continued
• Other information included in the station model are
the air temperature and the dew point.
• The dew point indicates how high the humidity of the
air is, or how much water is in the air.
• The station model also indicates the atmospheric
pressure by using a three-digit number in the upper
right hand corner.
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Section 4 Forecasting the Weather
Weather Maps, continued
The diagram below shows the different weather symbols used on weather
maps.
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Chapter 24
Section 4 Forecasting the Weather
Weather Maps, continued
Plotting Temperature and Pressure
• Lines that connect points of equal temperatures are
called isotherms.
• Lines that connect points of equal atmospheric
pressure are called isobars.
• The spacing and shape of the isobars help
meteorologists interpret their observations about the
speed and direction of the wind.
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Section 4 Forecasting the Weather
Weather Maps, continued
Plotting Fronts and Precipitation
• Most weather maps mark the locations of fronts and
areas of precipitation.
• Fronts are identified by sharp changes in wind speed
and direction, temperature or humidity.
• Areas of precipitation are commonly marked by using
colors or symbols.
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Section 4 Forecasting the Weather
Weather Maps, continued
The diagram below shows an example of a typical weather map.
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Chapter 24
Section 4 Forecasting the Weather
Reading Check
How do meteorologists mark precipitation on a weather
map?
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Chapter 24
Section 4 Forecasting the Weather
Reading Check
How do meteorologists mark precipitation on a weather
map?
Areas of precipitation are marked by using colors or
symbols.
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Chapter 24
Section 4 Forecasting the Weather
Weather Forecasts
• To forecast the weather, meteorologists regularly plot
to the intensity and path of weather systems on
maps.
• Meteorologists then study the must recent weather
map and compare it with maps from previous hours.
• By following the progress of weather systems,
meteorologist can forecast the weather.
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Chapter 24
Section 4 Forecasting the Weather
Weather Forecasts, continued
Weather Data
• Computers models can show the possible weather
conditions for several days.
• Comparing models helps meteorologists better
predict weather.
• By using computers, scientists can manipulate data
on temperature and pressure to simulate errors in
measuring these data.
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Chapter 24
Section 4 Forecasting the Weather
Reading Check
Why do meteorologists compare models.
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Chapter 24
Section 4 Forecasting the Weather
Reading Check
Why do meteorologists compare models.
Meteorologists compare computer models because
different models are better at predicting different
weather variables. If information from two or more
models matches, scientists can be more confident of
their predictions.
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Chapter 24
Section 4 Forecasting the Weather
Weather Forecasts, continued
Types of Forecasts
• Meteorologists make four types of forecasts.
• Daily forecasts predict weather conditions for a 48hour period. Extended forecasts look ahead 3 to 7
days. Medium range forecasts look ahead 8 to 14
days. Long-range forecasts cover monthly and
seasonal periods.
• Accurate weather forecasts can be made for 0 to 7
days. However, accuracy decreases with each day.
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Section 4 Forecasting the Weather
Weather Forecasts, continued
Severe Weather Watches and Warnings
• One main goal of meteorology is to reduce the
amount of destruction caused by severe weather by
forecasting severe weather early.
• A watch is issued when the conditions are ideal for
severe weather.
• A warning is given when severe weather has been
spotted or is expected within 24 hours.
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Chapter 24
Section 4 Forecasting the Weather
Controlling the Weather
• Some meteorologists are investigating methods of
controlling rain, hail, and lightning.
• Currently, the most researched method for producing
rain has been cloud seeding.
• Cloud seeding can also be used to prevent more
severe precipitation.
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Section 4 Forecasting the Weather
Controlling the Weather, continued
Hurricane Control
• Hurricanes have also been seeded with freezing
nuclei in an effort to reduce the intensity of the storm.
• During Project Stormfury, which took place from 1962
to 1983, four hurricanes were seeded, and the project
had mixed results.
• Scientists have, for the most part, abandoned storm
and hurricane control because it is not an attainable
goal with existing technology.
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Chapter 24
Section 4 Forecasting the Weather
Controlling the Weather, continued
Lightning Control
• Seeding of potential lightning storms with silveriodide nuclei has seemed to modify the occurrence of
lighting.
• However, no conclusive results have been obtained.
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Chapter 24
Maps in Action
Maps in Action
Weather-Related Disasters, 1980–2003
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Chapter 24
Standardized Test Prep
Multiple Choice
1. What tool do meteorologists use to analyze particle
movements within storms?
A.
B.
C.
D.
an anemometer
a radiosonde balloon
doppler radar
satellite imaging
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
1. What tool do meteorologists use to analyze particle
movements within storms?
A.
B.
C.
D.
an anemometer
a radiosonde balloon
doppler radar
satellite imaging
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
2. What kind of front forms when two air masses move
parallel to the boundary located between them?
F.
G.
H.
I.
an occluded front
a polar front
a warm front
a stationary front
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
2. What kind of front forms when two air masses move
parallel to the boundary located between them?
F.
G.
H.
I.
an occluded front
a polar front
a warm front
a stationary front
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
3. Which of the following weather systems commonly
forms over warm tropical oceans?
A.
B.
C.
D.
thunderstorms
hurricanes
tornadoes
anticyclones
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
3. Which of the following weather systems commonly
forms over warm tropical oceans?
A.
B.
C.
D.
thunderstorms
hurricanes
tornadoes
anticyclones
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
4. What often happens to maritime air masses as they
move inland over mountainous country?
F.
G.
H.
I.
They bring warm, dry weather conditions.
They produce clouds and hurricanes.
They bring cold, dry weather conditions.
They lose moisture passing over mountains.
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
4. What often happens to maritime air masses as they
move inland over mountainous country?
F.
G.
H.
I.
They bring warm, dry weather conditions.
They produce clouds and hurricanes.
They bring cold, dry weather conditions.
They lose moisture passing over mountains.
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
5. What type of air mass originates over the southweathern desert of the United States in summer?
A.
B.
C.
D.
continental polar air mass
continental tropical air mass
maritime polar air mass
maritime tropical air mass
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Chapter 24
Standardized Test Prep
Multiple Choice, continued
5. What type of air mass originates over the southweathern desert of the United States in summer?
A.
B.
C.
D.
continental polar air mass
continental tropical air mass
maritime polar air mass
maritime tropical air mass
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Chapter 24
Standardized Test Prep
Short Response
6. What type of front is formed when a warm air mass
is overtaken by a cold air mass, which causes the
warm air to lift above the cold air?
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Chapter 24
Standardized Test Prep
Short Response, continued
6. What type of front is formed when a warm air mass
is overtaken by a cold air mass, which causes the
warm air to lift above the cold air?
Cold front
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Chapter 24
Standardized Test Prep
Short Response, continued
7. What do closely spaced isobars indicate about the
wind on a weather map?
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Chapter 24
Standardized Test Prep
Short Response, continued
7. What do closely spaced isobars indicate about the
wind on a weather map?
high-speed winds
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Chapter 24
Standardized Test Prep
Interpreting Graphics
Use the diagram below to answer questions 11 and 12.
The diagram shows a station model.
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
11. What letter represents the current barometric
reading shown in the model?
A.
B.
C.
D.
letter A
letter B
letter C
letter D
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
11. What letter represents the current barometric
reading shown in the model?
A.
B.
C.
D.
letter A
letter B
letter C
letter D
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
12. What weather information do the symbols indicated
by the letters E and F provide? Interpret this part of
the station model.
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
12. What weather information do the symbols indicated
by the letters E and F provide? Interpret this part of
the station model.
E is wind direction, and F is wind speed. Currently,
the station model is showing a 30-knot wind that is
blowing in from south.
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
Use the diagram below to answer questions 13 and 14.
The diagram shows a home weather station.
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
13. Which of the following weather instruments shown
uses the cooling effect of evaporation to take
measurements.
A.
B.
C.
D.
a rain gauge
a psychrometer
a wind sock
a thermometer
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
13. Which of the following weather instruments shown
uses the cooling effect of evaporation to take
measurements.
A.
B.
C.
D.
a rain gauge
a psychrometer
a wind sock
a thermometer
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Interpreting Graphics, continued
14. Describe how an anemometer is used to calculate
wind speed.
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Chapter 24
Standardized Test Prep
Interpreting Graphics, continued
14. Describe how an anemometer is used to calculate
wind speed.
Answers should include: as the cups on the anemometer catch
the wind, the device begins to rotate; the speed of this rotation,
usually given in revolutions per minute, and the circumference
of the circle made by the cups are used to calculate wind
speed; rudimentary devices rely on the user to count the
revolutions per minute of the device and to perform the
necessary math to determine the wind speed; in modern
computerized devices, a number of factors may be considered
to obtain the most accurate measurement possible, including
the circumference of the device, friction of the air, and drag.
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Chapter 24
Air Masses
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Chapter 24
Stages of a
Midlatitude
Cyclone
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Chapter 24
Weather Symbols
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Chapter 24
Weather Map of the United States
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Chapter 24
Weather-Related Disasters, 1980-2003
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