1
th
Instructor's Manual and Test Bank to accompany Meteorology Today, 10 Edition
Jonathan D. W. Kahl
University of Wisconsin-Milwaukee
Chapter 9
Wind: Small Scale and Local Systems
Summary
A wide variety of types of small- and middle-scale wind motions are examined in this chapter,
ranging from short-lived microscale phenomena to the seasonal Asian monsoon system. The chapter
begins with a quick classification of the scales of atmospheric motion and looks at the formation of
eddies. A focus section on “Eddies and Air Pockets” examines the relationship between stability, vertical
wind shear, and clear-air turbulence, which can present a hazard to aviation.
Wind motions can have a variety of effects on the environment, such as lifting and transporting
soil, shaping sand dunes, and creating waves in the ocean. Relationships between wind and energy are
examined in separate focus sections on “Pedaling Into the Wind” and “Wind Power”. The curious
relationship between wind and melting snow is described in the focus section “Snow Eaters and Rapid
Temperature Changes”.
The formation of thermal circulations is covered in some detail. Sea, lake, and land breezes are
presented as examples of thermal circulations, and the effect that they can have on their surroundings is
examined. The Asian monsoon, which, in many ways, resembles a large scale thermal circulation, is
covered. Additional local scale wind systems including mountain and valley breezes, katabatic winds,
and the chinook are discussed, as is the relationship between sea breezes and widespread fires in Florida.
New material on the widespread fires in Southern California caused by the 2007 Santa Ana winds is
presented in this section.
The chapter concludes with descriptions of some of the methods used to measure wind speed and
direction at the ground and upper levels. A final focus section on “Observing Winds from Space”
describes the clever ways in which winds in remote areas of the Earth can be observed using satelliteborne instruments.
2
Teaching Suggestions
1.
Clouds produced by some of the mesoscale wind circulation patterns discussed in this chapter can
be seen on satellite images. Sea breeze convergence zones are often visible along the eastern or western
coastline of Florida. Ask students why a strong convergence zone will form along the west coast one day
and then along the east coast another day.
2.
Construct a box approximately 12" wide x 12" high x 4" deep. The front side of the box should
be constructed out of clear plastic. Place two "cat food" cans at opposite ends of the bottom of the box.
Fill one can with dark soil, the other with water. Place a 150 or 200 Watt bulb so that light shines equally
onto the two cans in the box. After a few minutes, carefully introduce some smoke into the chamber from
a hole near the middle of the bottom edge of the plastic. With some care, a circular circulation will be
visible.
3.
If there is a particularly windy area on campus, such as a ‘wind tunnel’ between adjacent
buildings, discuss the possible reasons for its existence.
4.
Ask students to give examples of weather phenomena within the different scales of motion
(microscale, mesoscale, synoptic-scale and planetary scale).
5.
Challenge students to describe visual examples of turbulence (they may need to be creative, as air
is invisible).
6.
Show the short (39 second) time-lapse video of clouds in the Canary Islands to the class and
discuss the role of turbulence in cloud formation:
http://www.youtube.com/watch?v=uTQwtY3XueI
7.
Find out if there are any sailors or pilots in your class. If so, ask them to describe their their
experiences with turbulence and other aspects of wind that are relevant to the course material.
8.
Examine satellite imagery of the Great Lakes region for evidence of land/lake breeze circulations.
9.
Discuss any small-scale wind circulations that affect your area.
10.
Show a graph of average annual rainfall for your area and, if possible, relate the rainfall pattern to
local wind circulations.
Student Projects
1.
Have students research and summarize the weather conditions that produce any local scale winds
that are unique to their area. Do these local winds have any important effects on the local climate?
2.
Have students determine the prevailing winds and construct a windrose for their city or town.
Can students find any evidence that data of this type has been used by city planners?
3.
Have students summarize the weather conditions prevailing during a period when strong Santa
Ana winds are being observed in southern California.
2
3
4.
Have students plot hourly wind data for their city for a period of several days. At what time of
day do the strongest winds occur? Have students discuss and interpret their findings.
5.
Identify the nearest location where you would expect a direct thermal circulation to form, and see
if you can find evidence of its existence using actual weather data.
Answers to Questions for Review
1.
Microscale: diameter of a few meters or less, time scale of seconds to a few minutes. Example:
turbulent eddies. Mesoscale: diameter of a few kilometers to hundreds of kilometers, time scale of hours
to a day. Example: thunderstorms. Synoptic scale: diameter of several hundred to a thousand kilometers,
time scale of days to weeks. Example: high and low pressure systems. Global scale: spatial scale of
entire earth, time scale of weeks to months. Example: longwaves in the westerlies.
2.
Through friction and the creation of turbulent eddies. Mechanically and thermally-generated
eddies can extend above the surface to disturb the flow aloft.
3.
Turbulent eddies.
4.
Eddy motions created by obstructions are called mechanical turbulence. Vertical motions caused
by surface heating and instability are called thermal turbulence.
5.
Thermally-generated turbulent eddies typically peak in the afternoon when surface temperatures
reach their maximum.
6.
Winds blowing over obstacles, convection, wind shear.
7.
The plane apparently flew through a portion of a turbulent eddy containing strong downdrafts.
8.
The barrier could cause a turbulent eddy, creating a strong wind from the west.
9.
Wind shear is the change in wind speed or direction with increasing altitude. When the shear
exceeds a critical value, waves break into large swirls with significant vertical movement. When this
happens in clear air it's called clear air turbulence.
10.
Shelterbelts usually consist of a series of mixed conifer and deciduous trees or shrubs planted in
rows perpendicular to the prevailing wind flow. They greatly reduce the wind speed behind them. As air
filters through the belt, the flow is broken into small eddies, which have little mixing effect on the air near
the surface.
11.
Wind striking an object exerts a pressure on it. The amount of pressure depends upon the object's
shape and size, and also on the amount of reduced pressure that exists on the object's downwind side. A
camper has a larger area than a car, thus will experience a greater force by the wind. Also, the pressure
drop on the downwind side will be greater for the camper than for the car, allowing the camper to be
moved further.
12.
Wind waves are created as the frictional drag of the wind transfers energy to the water surface
below.
4
13.
Strong winds far offshore can create waves which extend for many miles, even to areas which are
not experiencing strong winds.
14.
As air moves from the rough land over relatively smooth water, friction with the surface lessens,
and the wind speed increases. The increase in wind speed increases the Coriolis force, which turns the
wind flow to the right.
16.
Valley breeze, because rising air will expand and cool adiabatically.
17.
Chinook winds blow down mountain slopes. As air descends it warms adiabatically. Chinook
winds are dry because the air's moisture has been lost as the air ascended on the upwind side of the
mountain.
18.
Chinooks bring relief from the cold, expose vegetation for grazing animals, keep railroad tracks
clear of snow.
19.
As air descends from the elevated desert plateau, it funnels through mountain canyons in the San
Gabriel and San Bernardino Mountains, finally spreading over the Los Angeles basin and San Fernando
Valley. The wind often blows with exceptional speed in the Santa Ana Canyon (the canyon from which it
derives its name). These warm, dry winds develop as a region of high pressure builds over the Great
Basin. The clockwise circulation around the anticyclone forces air downslope from the high plateau.
Santa Ana winds are warm because of compressional heating of the already warm, dry desert air.
20.
The ideal setting for a katabatic wind is an elevated plateau surrounded by mountains, with an
opening that slopes rapidly downhill. When winter snows accumulate on the plateau, the overlying air
grows extremely cold and a shallow dome of high pressure forms near the surface. Along the edge of the
plateau, the horizontal pressure gradient force is usually strong enough to cause the cold air to flow across
the isobars through gaps and saddles in the hills. Along the slopes of the plateau, the wind continues
downhill as a gentle or moderate cold breeze. If the horizontal pressure gradient increases substantially,
such as when a storm approaches, or if the wind is confined to a narrow canyon or channel, the flow of air
can increase, often destructively, as cold air rushes down-slope like water flowing over a waterfall.
21.
Because there is more sand and dust in Arizona.
22.
Dust devils form on clear, hot days over a dry surface where most of the sunlight goes into
heating the surface, rather than evaporating water from vegetation. The atmosphere directly above the hot
surface becomes unstable, convection sets in, and the heated air rises. Wind, often deflected by small
topographic barriers, flows into this region, rotating the rising air. Depending on the nature of the
topographic feature, the spin of a dust devil around its central eye may be cyclonic or anticyclonic, and
both directions occur with about equal frequency.
23.
During the winter, the air over the continent becomes much colder than the air over the ocean. A
large, shallow high-pressure area develops over continental Siberia, producing a clockwise circulation of
air that flows out over the Indian Ocean and South China Sea. Subsiding air of the anticyclone and the
downslope movement of northeasterly winds from the inland plateau provide eastern and southern Asia
with generally fair weather. Hence, the winter monsoon, which lasts from about December through
February, means clear skies (dry season), with winds that blow from land to sea. In summer, the wind
flow pattern reverses itself as air over the continents becomes much warmer than air above the water. A
shallow thermal low develops over the continental interior. The heated air within the low rises, and the
surrounding air responds by flowing counterclockwise into the low center. This condition results in
4
5
moisture-bearing winds sweeping into the continent from the ocean. The humid air converges with a drier
westerly flow, causing it to rise; further lifting is provided by hills and mountains. Lifting cools the air to
its saturation point, resulting in heavy showers and thunderstorms. Thus, the summer monsoon of
southeastern Asia, which lasts from about June through September, means wet, rainy weather (wet
season) with winds that blow from sea to land.
24.
Northwest.
25.
Watching the movement of objects in the air, measuring the rate of evaporation of liquid water
into the air, listening to sounds traveling with the wind, sniffing for smells carried by the wind, measuring
speed or direction with meteorological instruments.
26.
Wind vane: a long arrow with a tail, which is allowed to move freely about a vertical post. Cup
anemometer: three (or more) hemispherical cups (cup anemometer) mounted on a vertical shaft. The
difference in wind pressure from one side of a cup to the other causes the cups to spin about the shaft. The
rate at which they rotate is directly proportional to the speed of the wind. The spinning of the cups is
usually translated into wind speed through a system of gears, and may be read from a dial or transmitted
to a recorder. Aerovane: an instrument that indicates both wind speed and direction. It consists of a
bladed propeller that rotates at a rate proportional to the wind speed. Its streamlined shape and a vertical
fin keep the blades facing into the wind. When attached to a recorder, a continuous record of both wind
speed and direction is obtained.
27.
North.
28. With the aid of Doppler radar a vertical profile of wind speed and direction up to an altitude of 16
kilometers or so above the ground can be obtained. Such a profile is called a wind sounding, and the
radar, a wind profiler (or simply a profiler). Doppler radar, like conventional radar, emits pulses of
microwave radiation that are returned (backscattered) from a target, in this case the irregularities in
moisture and temperature created by turbulent, twisting eddies that move with the wind. Doppler radar
works on the principle that, as these eddies move toward or away from the receiving antenna, the
returning radar pulse will change in frequency. The Doppler radar wind profilers are so sensitive that they
can translate the backscattered energy from these eddies into a vertical picture of wind speed and
direction in a column of air 16 km (10 mi) thick.
29. Geostationary satellites positioned above a particular location show the movement of clouds. The
direction of cloud movement indicates wind direction, and the horizontal distance the cloud moves during
a given time period indicates the wind speed. Satellites now measure surface winds above the ocean by
observing the roughness of the sea.
30.
(a) Alps; warm, dry winds.
(b) California central valley; extremely hot winds.
(c) Southern California; hot, dry wind.
(d) Argentina; warm, dry downslope winds.
(e) Front range of the Rocky Mountains; warm dry winds.
(f) Columbia River gorge; strong cold katabatic wind.
(g) Mediterranean; warm, humid wind.
(h) France's Rhone Valley; cold wind.
6
Answers to Questions for Thought
1.
Probably in the early morning before sunrise when the atmosphere is most stable and thermal
turbulence is at a minimum.
2.
Turbulent eddies form on the leeward side of a hill during periods of strong winds. The
downward motion of the eddies can cause a hang-glider to crash into the ground or along the side of a
hill.
3.
North, south, and east of Cheyenne, Wyoming, are fairly flat plains (mountains lie to the west).
High winds pick up and carry some of the snow deposited on the plains. A town on the plains (with its
trees, buildings, and so on) acts as an obstruction to the wind. Hence, the wind slows over the town and
deposits a portion of the blowing snow it was carrying. This of course, adds to the town's total snow
accumulation.
4.
In clear weather there is usually a greater variation in atmospheric stability between morning and
afternoon. Mornings are often characterized by a stable radiation inversion, and afternoons by an
unstable atmosphere and strong vertical mixing. The greater atmospheric instability on clear days tends
to link surface air with the air above and produce greater surface wind speeds. On overcast days the
earth's surface does not warm as much, the atmosphere is more stable, and much less vertical mixing
occurs.
5.
Since a city contains more concrete buildings and paved roads than the suburbs, the city would
heat up during the day and be warmer than the surrounding suburbs. This would produce a daytime
“suburb breeze” directed from the suburbs toward the city. At night, when the city cools, a “city breeze”
would result.
6.
City A is the best site for a wind turbine. Here the winds appear to be steadier, yet strong enough
to produce electricity throughout a 24-hour day.
7.
Site B is the best site to construct a wind turbine; Site C is the worst. The wind blows strongest at
Site B and is most turbulent and gusty at Site C.
8.
Well-developed sea breezes are due to large daytime temperature and pressure differences that
exist between the cool water and the warm land. If the water is quite cool, at night the land will be unable
to cool to a temperature lower than that of the water. Consequently, at night pressure differences will be
small and a land breeze will be unlikely.
9.
With a sea breeze, the air is rising over land and sinking over water. With a land breeze, the air is
rising over water and sinking over land.
10.
The air moving inland over Florida is more unstable and contains more water vapor than does the
air moving inland over California, off the cool Pacific Ocean. Only slight lifting will produce clouds in
the humid, unstable Florida air.
11.
The Appalachian Mountains are much lower in elevation than are the Rocky Mountains. Less
dramatic warming of air occurs on the eastern side of the Appalachians. Also, the Appalachians do not
effectively "shield" the eastern side from clouds, precipitation and humid air.
6
7
12.
For hot summer breezes from the north, the area should have a high topographic barrier, such as a
high plateau, to the north. In addition, high surface pressure should be to the north. As the wind blows
clockwise around the high, it moves southward (which is downhill). The sinking air is compressed, so it
warms, producing high air temperatures.
13.
The strongest sea breezes should be along Florida's east coast. The strongest land breeze should
be along Florida's west coast.
Answers to Critical Thinking Questions
Figure 9.23.
Breakfast. The time must be just after sunrise. The rising sun is shining on the east side
of the hill, warming the ground and creating an upslope valley breeze. On the western side of the hill it is
still dark, in the final stages of a downslope mountain breeze.
Figure 9.29.
Adiabatic warming causes temperatures to rise as the air blows downhill. Red Bluff must
be in a valley (lower elevations), allowing for more downslope motions and thus more warming. A
subsidence inversion could have prevented cooler air aloft from mixing with the hot air.
8
Multiple Choice Exam Questions
1.
An example of mesoscale motion is
a. winds on a surface weather map of North America.
b. winds on a 500 mb chart.
c. winds blowing through a city.
d. winds blowing past a chimney.
e. average wind patterns around the world.
ANSWER: C
2.
An example of microscale motion is
a. winds on a surface weather map of North America.
b. winds on a 500 mb chart.
c. winds blowing through a city.
d. winds blowing past a chimney.
e. average wind patterns around the world.
ANSWER: D
3.
Which of the following associations is most accurate?
a. microscale - chinook wind
b. synoptic scale - sea breeze
c. mesoscale - land breeze
d. planetary scale - lake breeze
ANSWER: C
4.
The slowing of the wind due to the random motion of air molecules is called
a. eddy viscosity.
b. mechanical turbulence.
c. molecular viscosity.
d. convective turbulence.
ANSWER: C
5.
Thermal turbulence above the surface is usually most severe
a. immediately after sunset.
b. at the time of maximum surface heating.
c. around midnight.
d. just before sunrise.
e. about midmorning, or soon after the minimum temperature is reached.
ANSWER: B
6.
On a clear, windy day, the depth to which mixing occurs above the surface depends upon
a. the wind speed.
b. surface heating.
c. the landscape.
d. all of the above
ANSWER: D
8
9
7.
Surface winds are generally strongest and most gusty
a. in the afternoon.
b. in the early morning.
c. around midnight.
d. just after sunset.
e. just before sunrise.
ANSWER: A
8.
The wind's speed generally increases with height above the earth's surface because
a. only the lowest layer of air rotates with the earth.
b. air temperature normally decreases with height.
c. wind instruments are not accurate at the earth's surface.
d. friction with the earth's surface slows the air near the ground.
e. air parcels expand and become less dense as they rise above the surface.
ANSWER: D
9.
The howling of wind on a blustery night is believed to be caused by
a. variation in air temperature.
b. wind blowing around a frozen surface.
c. snowflakes striking one another but not sticking together.
d. eddies of higher air density.
e. wind lifting, then lowering small objects at the surface.
ANSWER: D
10.
Clear Air Turbulence (CAT) can occur
a. near a jet stream.
b. in areas of mountain waves.
c. where strong wind shear exists.
d. all of the above
ANSWER: D
11.
Which below is not true concerning an "air pocket"?
a. can form in a downdraft of an eddy
b. often form in the atmosphere where the air is too thin to support the wings of an airplane
c. often form in regions that exhibit strong vertical wind shear
d. can develop in clear air
ANSWER: B
12.
Clear air turbulence often occurs near a boundary of high wind shear.
a. true
b. false
ANSWER: A
13.
The size and shape of a turbulent eddy depend on
a. the size of the obstacle.
b. the shape of the obstacle.
10
c. the speed of the wind.
d. all of the above
e. only size and shape of the obstacle.
ANSWER: D
14.
Suppose the wind speed increased from 5 mph to 10 mph. We can conclude that the force exerted
by the wind increased by a factor of
a. 2.
b. 4.
c. 5.
d. 25.
ANSWER: B
15.
If huge waves pound against the beach communities of Southern California for several days
during clear, calm weather, it is a good bet that
a. the winds are strong somewhere out over the Pacific Ocean.
b. an earthquake has occurred somewhere on the ocean floor.
c. it is raining offshore.
d. it is a period of high tides.
e. there is a large difference in water density between the shoreline of Southern California
and the middle of the Pacific.
ANSWER: A
16.
Which below has the least influence on determining how high a wind wave will grow over the
open ocean?
a. fetch of water
b. density of water
c. length of time the wind blows over the water
d. wind speed over the water
ANSWER: B
17.
Which of the features below could indicate prevailing wind direction?
a. sand ripples
b. sand dunes
c. "flag" trees
d. all of the above
ANSWER: D
18.
Dust storms and dust devils are ____ on Mars.
a. infrequent
b. extremely rare
c. common
ANSWER: C
19.
A wind rose indicates
a. the wind speed at a location at a particular time.
b. the percentage of time that the wind blows from different directions.
10
11
c. observed wind speed and direction on a surface map.
d. spinning wind patterns caused by buildings or other obstructions.
ANSWER: B
20.
The most practical location for building a wind turbine would be
a. in a region of strong, gusty winds.
b. on the downwind side of a mountain.
c. in a narrow valley.
d. in a region of moderate, steady winds.
ANSWER: D
21.
An offshore wind
a. blows from land to water.
b. blows from water to land.
c. blows only at night.
d. only blows during the day.
ANSWER: A
22.
A wind reported as 45 would be a wind blowing from the:
a. NE.
b. S.
c. SW.
d. NW.
e. E.
ANSWER: A
23.
Suppose a west wind of 20 knots blows over a coastal region which is densely covered in shrubs.
If this same wind moves out over the middle of a large calm lake, its speed and direction would probably
be
a. greater than 20 knots and more northwesterly.
b. less than 20 knots and more northwesterly.
c. greater than 20 knots and more southwesterly.
d. less than 20 knots and more southwesterly.
e. less than 20 knots and westerly.
ANSWER: A
24.
Which is not a characteristic of a thermal low?
a. forms in a region of warm air
b. forms in response to variations in surface air temperature
c. becomes stronger with increasing height
d. lowest pressure is at the center
ANSWER: C
25.
During the summer in humid climates, nighttime clouds tend to form over water during a
a. land breeze.
b. chinook wind.
c. sea breeze.
12
d. Santa Ana wind.
ANSWER: A
26.
A sea breeze circulation will reverse direction and become a land breeze
a. once every few days.
b. at the beginning and the end of the summer.
c. several times per day.
d. once per day.
ANSWER: D
27.
A sea or land breeze is caused by
a. differences in humidity.
b. temperature differences.
c. the Coriolis force.
d. ocean tides.
e. strong surf conditions.
ANSWER: B
28.
The nighttime counterpart of the sea breeze circulation is called a
a. chinook.
b. Santa Ana.
c. land breeze.
d. night breeze.
e. foehn.
ANSWER: C
29.
In south Florida the prevailing winds are northeasterly. Because of this, the strongest sea breeze is
usually observed on Florida's ____ coast, and the strongest land breeze on Florida's ____ coast.
a. east, west
b. west, east
c. west, west
d. east, east
ANSWER: A
30.
When a sea breeze moving north meets a sea breeze moving south, they form a
a. land breeze.
b. sea breeze convergence zone.
c. katabatic wind.
d. valley breeze.
ANSWER: B
31.
Clouds and precipitation are frequently found on the downwind side of a large lake. This would
indicate that the air on the downwind side is
a. converging and rising.
b. converging and sinking.
c. diverging and sinking.
d. diverging and rising.
12
13
ANSWER: A
32.
During the summer along the coast, a sea breeze is usually strongest and best developed
a. in the afternoon.
b. just after sunrise.
c. just before sunset.
d. just before noon.
e. around midnight.
ANSWER: A
33.
The summer monsoon in eastern and southern Asia is characterized by
a. wet weather and winds blowing from land to sea.
b. dry weather and winds blowing from land to sea.
c. wet weather and winds blowing from sea to land.
d. dry weather and winds blowing from sea to land.
ANSWER: C
34.
The winter monsoon in eastern and southern Asia is characterized by
a. wet weather and winds blowing from land to sea.
b. wet weather and winds blowing from sea to land.
c. dry weather and winds blowing from sea to land.
d. dry weather and winds blowing from land to sea.
ANSWER: D
35.
Low pressure becomes best developed over the Asian continent in
a. summer.
b. winter.
c. fall.
d. spring.
ANSWER: A
36.
While fly fishing in a mountain stream, you notice that the wind is blowing upstream. From this
you could deduce that the wind is a
a. chinook wind.
b. valley breeze.
c. Santa Ana wind.
d. mountain breeze.
e. katabatic wind.
ANSWER: B
37.
Cumulus clouds that appear above isolated mountain peaks are often the result of
a. katabatic winds.
b. mountain winds.
c. fall winds.
d. Santa Ana winds.
e. valley breezes.
14
ANSWER: E
38.
A valley breeze would develop its maximum strength
a. at sunrise.
b. in early afternoon.
c. about an hour after sunset.
d. about midnight.
ANSWER: B
39.
A katabatic wind is a ____ and ____ wind.
a. cold, upslope
b. warm, upslope
c. cold, downslope
d. warm, downslope
ANSWER: C
40.
The heat from a chinook wind is generated mainly by
a. compressional heating.
b. sunlight.
c. warm, ocean water.
d. friction with the ground.
e. forest fires.
ANSWER: A
41.
On the eastern side of the Rocky Mountains, chinook winds are driest when
a. clouds form and precipitation falls on the upwind side of the mountains.
b. the air aloft is cold.
c. the sun is shining.
d. the winds are blowing from the east.
e. surface friction is greatest on the downwind side of the mountain.
ANSWER: A
42.
Chinook winds are
a. warm, dry downslope winds.
b. warm, moist downslope winds.
c. cold, dry downslope winds.
d. cold, moist downslope winds.
e. warm, dry upslope winds.
ANSWER: A
43.
Santa Ana winds warm by ____ as they flow down an elevated desert plateau.
a. expansion
b. compression
c. evaporation
d. both expansion and evaporation
ANSWER: B
14
15
44.
Which of the following conditions favor the development of dust devils?
a. hot, moist days
b. hot, dry days
c. cold, moist days
d. cold, dry days
ANSWER: B
45.
A northeaster along the east coast of the United States is best developed when a low pressure area
a. moves from west to east over Canada.
b. moves eastward over the Great Lakes.
c. moves northward over Ohio.
d. moves northeastward from the Texas panhandle.
e. moves northeastward over the Atlantic Ocean adjacent to the coast.
ANSWER: E
46.
A sea breeze is most likely to develop along a coastline when
a. away from the shore, pressure gradients are large.
b. away from the shore, pressure gradients are small.
c. it is raining.
d. it is foggy.
ANSWER: B
47.
Which of the following is a serious hazard to aircraft?
a. molecular viscosity
b. laminar flow
c. clear-air turbulence
d. longwaves in the westerlies
e. none of the above
ANSWER: C
48.
Good hang-gliding conditions require
a. thermal turbulence.
b. upward air motions.
c. molecular viscosity.
ANSWER: B
49.
The land/sea breeze, lake breeze, and mountain/valley breeze are examples of
a. thermal circulations.
b. mechanical circulations.
c. atmospheric longwave circulations.
ANSWER: A
50.
Strong winds blowing over vegetation results in
a. physically damaged plants.
b. decreased crop productivity.
c. rapid water loss.
d. all of the above
16
ANSWER: D
Essay Exam Questions
1.
You are hiking on a mountain trail at sunrise when you smell the smoke from cooking bacon.
You can't see where the smoke is coming from. Would you expect the camp to be above you or
below you on the mountain? Explain.
2.
List the scales of atmospheric motion from largest to smallest and give an example of each. From
what you know about the various types of wind systems, are the size and duration related?
3.
What is clear air turbulence (CAT)?
aviation?
4.
Draw a sketch to show where eddies can form when air blows rapidly over a mountain range.
Show on your sketch where you might expect clouds to form. How would these clouds appear
when viewed from the ground?
5.
Summertime weather forecasts for cities on the shores of the Great Lakes often contain the phrase
“cooler near the lake”. Explain the relevance of this phrase.
6.
How might knowledge of the direction of the prevailing wind at a given location be used in
landscape design or the design of an energy efficient home?
7.
Would you expect a well-developed sea breeze circulation to cause clouds to form over the land
or over the ocean?
8.
Briefly sketch or describe the formation of a chinook wind. Would you expect chinook winds to
form more often on the eastern or the western slopes of the Cascade Mountains in Oregon?
9.
Briefly sketch or describe the conditions that lead to the formation of a Santa Ana wind. Is the
Santa Ana wind dry or moist, warm or cold?
10.
What is meant by the term monsoon wind system? Briefly describe or sketch the wind and
pressure pattern during the summer and winter monsoon in Asia.
11.
Will a valley breeze or a mountain breeze produce clouds? Explain.
12.
Explain how Florida’s sea breezes can increase the potential for wildfires.
13.
Areas along the shores of the Great Lakes often experience a lake breeze circulation. Are these
winds different than those associated with a sea breeze circulation? Explain.
14.
How can winds be observed by satellites?
15.
When air flows over a mountain range, why do clouds tend to form on the upwind rather than on
the downwind side of the range?
Why does clear air turbulence represent a hazard to
16