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Salt Lake Community College
Geography 1000 – Physical Geography
Spring, 2015 - AJ Allred, Adjunct
Student Name __________________
Quiz #7
Explanations
1. Which of the following statements is false?
a. A ‘thermal high’ involves heating that causes air to pressurize, then press outward
as wind.
b. A ‘thermal low’ is typically involved with relatively warmer and/or more humid
air.
c. A ‘thermal high’ tends to result when dense or colder air sinks lower in the
atmosphere.
d. A ‘dynamic low’ is most likely caused by either solar heating or humidity.
e. A ‘dynamic high’ is often caused by dry air that sinks toward the surface.
In a world with no “lid”, air that is heated will rise, causing low pressure instead of high
pressure that would otherwise result from heating a confined space.
Air that is relatively warmer and more humid will tend to rise – a dynamic low.
Sinking air is a dynamic high. Air that is cold or dry is a thermal high, because it is more
dense that humid or warmer air.
2. Hadley cell circulation is the main reason why _____________
a. Florida and Alabama have a mild climate with plenty of green landscapes.
b. Arizona is dry.
c. Regions near the Equator are rainy and humid.
d. Answers ‘b’ and ‘c’ above are correct.
e. Answers ‘a’ and ‘b’ above are correct.
Hadley cell circulation tend to promote dry climate near 30 degrees latitude, south and north
of the Equator. Arizona’s dry weather is one result.
Florida and Alabama should be dry also, but receive trade wind humidity instead. So, they
are warm and humid instead of hot and dry.
3. Regions near the Equator tend to show the world’s greatest daily and annual temperature
variations because they are exposed to vast solar energy that converts from mostly short
wave radiation to longer-wave thermal energy (heat you can feel).
True ___
False ___
Equatorial regions experience year-round conditions where sunshine is almost always
overhead. With abundant ocean expanse along most of the Equator, the combination of heat
and humidity results in mild conditions and daily rainfall.
Mildness also results from evaporative cooling as sunshine vaporizes water, and cooling
from cloud cover that eventually results from humidity.
4. Drought in California and others parts of the sunny southwestern USA __________.
a. can be caused when a low-pressure cyclone trough or depression ‘stalls’ or persists over
the region for long periods of time.
b. Can be caused when a high-pressure cell of anti-cyclonic air persists over the region
c. When trade winds are extra strong, pushing warm, dry air from the Atlantic that
evaporates available soil moisture
d. When the sub-tropical jet and polar jet combine to push strong, dry winds from the west
that are sometimes called the “Pineapple Express”
e. None of the above is at all associated with drought conditions in the western USA.
Persistent high air pressure will tend to bring persistent dry, sunny weather, the opposite of a
storm. Trade winds tend to bring moisture and warmth from the ocean to places along the
U.S. eastern seaboard and Gulf coasts.
If a cyclone ‘stalls’ or stabilizes over one place, then stormy weather also stalls there.
Jet streams from the west can sometimes bring rapidly moving humid air from the Pacific
Ocean to the western United States, resulting in sudden heavy precipitation that may be
called the “Pineapple Express”.
5. A “dry line” storm _______________:
a. is weaker than most mid-latitude cyclones due to relative lack of available moisture
b. is weaker than most mid-latitude cyclones because colliding air masses on both sides of
the storm boundary are much drier than usual
c. refers to dry conditions that develop after a mid-latitude cyclone has occluded completely
and nearly all moisture has left the air.
d. reflects the fact that one air mass has a much lower dew point than the opposing air mass
e. All of the above are true of “dry line” storms.
6. Air with a dew point temperature of 88°F is much less likely to produce a storm than air
with a dew point temperature of 24°F.
True ___
False ___
Air that reaches vapor saturation at very high temperature contains so much moisture that a
small drop in temperature is sufficient to begin the condensation process that leads to release
of latent heat for more rising. That process can result in high winds and heavy precipitation
as light-weight air rises quickly and continues to condense-out more vapor to water and more
latent heat to sensible heat.
Air that is so dry that condensation cannot be produced until temperature drops below
freezing is not likely to produce stormy weather. Instead, it can contribute to a storm by
colliding with warmer, wetter air, helping that more buoyant air to rise even faster.
A “dry line” storm is not dry at all, but instead represents a collision zone between air masses
that differ greatly in humidity.
See notes to Question 11 below.
7. The change in climate resulting from moving thousands of miles further north or further
south of the Equator may also be accomplished in a general way by moving closer to the
coast of any ocean.
True ___
False ___
According to “Mr. Allred’s Climate Rules” weather and climate become more severe with
distance from the Equator, and with distance from the ocean and from sea level.
So, moving thousands of miles further from the Equator should result in more severe weather
and climate. Moving closer to an ocean coastline should produce milder weather.
8. Citrus crops are found further north in California than in Florida because cP air masses
are more likely to cause frost in Florida than in California.
True ___
False ___
Because of westerly winds and mountain ranges, most of California does not receive
invading Arctic cold air masses as often as Florida does. So, killing frost is more common in
Florida even where tropical conditions prevail most of the time.
The safe zone for growing citrus is further north in California than in Florida.
9. In most cases, commercial jet airplanes can fly faster from Los Angeles to New York than
on the return flight back to L.A.
True ___
False ___
Westerly winds include a core of high-speed jet streams that also move toward the east, at
altitudes that can be reached by high-flying jet airliners. These same winds will tend to cause
a head wind for west-bound airplanes.
10. In the northern hemisphere, mid-latitude cyclones _____________
a. are more vigorous during a warm front because warm air contains more energy
than does cold air
b. are more vigorous with a cold front than with a warm front
c. will be fairly dry if a stationary front develops
d. will produce vast amounts of rain or snow after an occluded front develops
e. Answers ‘a’ and ‘c’ are both true.
Warm fronts tend to be milder than cold fronts because invading warm air is spread over a
broader cross-section of adjacent cooler, drier air. Cold fronts tend to be more blustery
because the collision zone is more vertical, with more rapidly rising air at the interface.
A stationary front is simply not moving, so continuing precipitation can accumulate, leading
to flooding. An occluded front represents the end of a storm, as warm air is now aloft and
cooler air dominates below. With neither air mass moving, a temporary inversion is in place.
Unstable conditions should begin to develop the next day as solar energy warms Earth’s
surface and causes air to rise.
11. Which of the following combinations of colliding air masses is/are likely to produce a
tornado or other severe weather?
a. Dew point at 25°F in one air mass and dew point at 75°F in the other air mass
b. Surface air pressure below 800 mb in both air masses
c. Surface air pressure below 700 mb in one air mass and above 1200 mb in the opposing
air mass
d. None of the options above are associated with severe weather
e. All of the conditions above are likely to produce severe weather
A severe difference in dew point temperature is typical of “dry line” storms that can include a
tornado or other severe weather.
Air is considered very dry if it can’t condense moisture until the temperature drops below
freezing, Meanwhile, if an adjacent air mass only has to cool a few degrees in order to reach
vapor saturation, then it will rise easily as cooler, drier air pushes in underneath.
A storm will be more vigorous if there is greater contrast between air masses.
The highest and lowest recorded air pressures on Earth vary between about 1080 mb and 855
mb, so any exam answers that reference pressure beyond those bounds are not good options.
See notes to Question 6 above.
12. As a mid-latitude cyclone pushes into Utah from Nevada, high pressure in Wyoming can
cause wind damage in Utah. After the cyclone passes through Utah and into Wyoming low
pressure in the storm can cause wind damage in Utah.
True ___
False ___
Low-pressure cyclones are ‘fed’ air from corresponding high-pressure areas nearby. So, an
approaching storm from the west can draw in windy conditions from high-pressure
conditions located somewhere to the east.
After a cyclone passes through Utah, the ‘back side’ of the storm can deliver windy
conditions from the northeast as well.
So, even though mid-latitude cyclones tend to arrive from the west, windy conditions can
push in from the east as well.
13. The islands of Great Britain have a more severe climate than locations at the same latitude
that are located deep within large land masses.
True ___
False ___
The British Isles are located far enough north to have a severely cold, humid climate, were it
not for the Gulf Stream that brings warm water northward. So, Great Britain has relatively
milder weather than locations at the same latitude that are deep within a continental land
mass.
14. A “blocking high” can contribute to drought in one location while simultaneously
promoting flooding in an adjacent low-pressure system.
True ___
False ___
Ordinarily, low-pressure mid-latitude cyclones and their opposing high-pressure cells and
ridges keep moving eastward with westerly winds. However, a cell or ridge of high pressure
air can persist over an area long enough to block the arrival of low-pressure cyclones that
provide precipitation.
If a cyclone is unable to move forward because of a “blocking high”, then a cyclone
somewhere to the west will also be unable to move forward. Precipitation over one spot may
persist long enough to cause flooding.
15. The north edges of the ‘A’ Tropical climate zone experience their annual dry season:
a. In June rather than December
b. In December rather than June
c. When the ITCZ is closest to India
d. When the ITCZ is not in effect (during summer and winter solstices)
e. During the monsoon season in Utah and Arizona
As the ITCZ migrates southward toward its December furthest latitude, regions just north of
the Equator are furthest from the rainy conditions provided by the ITCZ. So, places at the
edge of the tropical zone tend to have a dry season when the ITCZ is furthest away on the
other side of the Equator.
The ITCZ is always in effect, just not in the same places. In June, the ITCZ is typically north
of the Equator because the overhead location of the Sun is also in the northern hemisphere at
that time. So, places just north of the Equatorial zone will have their rainy season during
summer, and dry season during winter.
Even Arizona and Utah can have a monsoon season during summer when the ITCZ is in the
northern hemisphere. Humid conditions from the Gulf of Mexico and/or Pacific Ocean can
invade our normally dry realm, bring summer thunderstorms.
16. A trough or depression can lead to a hurricane or other severe weather because
________.
a. a trough or depression represents sinking air that sets up high winds
b. a tropical depression represents heavy air at the surface that spreads out in all
directions as a storm develops
c. air is converging and lifting
d. an ‘easterly wave’ builds high pressure for storm development and expansion
e. Answers ‘a’ and ‘b’ are both correct
An atmospheric ‘trough’ or ‘depression’ is about low numbers, not low air. Lower air
pressure readings (like 990mb compared to 1020mb) are low readings, but rising air.
An easterly wave represents converging air due to lifting, resulting in measured falling air
pressure numbers.
Rising air tends to be lighter-weight than drier, heavier air.
17. “Super Storm Sandy” in 2012 was an unusual hurricane because it continued to
gain energy as it moved northward into cooler waters of the North Atlantic Ocean.
True ___
False ___
Hurricane Sandy had diminished below hurricane strength as it passed near dry land and over
colder water. Collision with a ‘Nor ‘easter’ storm near New York provided cold air aloft that
encouraged remaining storm energy to lift rapidly, strengthening the storm without actually
adding energy.
18. How would climate change if a long-term or permanent “El Niño” condition were in
effect?
a. Ski season in Utah would be much more successful and popular.
b. Fishing along the Chilean coast of South America would be much less successful.
c. There would be fewer typhoons in the Philippines and other parts of the western
Pacific Ocean basin.
d. The west coast of North America would probably be more like Georgia, Alabama
and Florida.
e. All of the above are true.
When trade winds fail to push warm water and moist air westward across the Pacific Ocean,
stormy weather does not develop as much on the far, western side of the ocean. Instead,
those more precipitation occurs along the normally dry western edges of the western
hemisphere. Southwestern U.S. states, including Utah, will be wetter than usual.
Persistent El Niño conditions would eventually change dry climatic conditions to something
more like the U.S. eastern seaboard that is green and humid. The far side of the Pacific
Ocean would tend to drought and fewer typhoons and fishing in Chile and Peru would suffer
for lack of nutrients being drawn to the surface by ocean currents ‘pulled’ westward by the
trade winds.
19. When water evaporates, its physical structure changes, causing bonds of cohesion to
strength as sensible heat becomes latent within each water molecule.
True ___
False ___
Cohesion bonds are weak and break easily when water vaporizes. Converting sensible heat
to latency during evaporation provides the energy needed for this altered, more kinetic state
of water.
20. Acidity in air and water are a threat to ocean coral, land animals and even buildings
made of limestone. Rising levels of acidity are closely associated with human-caused
air pollution.
True ___
False ___
Air emissions from human activity tend to be acidic: oxides of nitrogen and sulfur are
contributors to “acid rain” and help form corrosive ozone. Even carbon dioxide emissions
tend to promote acidic conditions. The world’s oceans are becoming more acidic, with
effects on plant and animal communities that evolved under conditions that were more
alkaline (basic). Limestone and other calcium-related structures, including coral reefs and
bone are easily eroded by acidic conditions.