Salt Lake Community College
Geography 1000 – Physical Geography
AJ Allred, Adjunct
Student Name __________________
Quiz #7
1. Which of the following statements is true regarding atmospheric pressure?
a. High air pressure typically results from hot weather.
b. Low air pressure results in cold, dry weather.
c. High air pressure is often caused by cold, dry air.
d. A region with persistent high air pressure tends to experience frequent severe
storms, including heavy rain.
e. All of the above are true.
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 amounts of solar energy.
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 result when a low-pressure cyclone ‘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. results when trade winds are extra strong, pushing dry air from the Atlantic Ocean that
dries out soils and damages crops.
d. is caused by the “Pineapple Express”
e. None of the above are 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 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.
d. results from one air mass being much more humid than an adjacent air mass
e. All of the above are true of “dry line” storms.
6. Which of the following combinations of weather conditions is mostly likely to result in a
“dry line” storm? (Hint: Remember that contrast between air masses is a key factor in
creating vigorous, even violent weather.)
a. One air mass at 80°F and 40% humidity, and adjacent air at 60°F with 60% humidity
b. One air mass at 90°F and 20% humidity and adjacent air at 91°F with 15% humidity
c. One air mass at 80°F and 40% humidity and adjacent air at 90°F with 70% humidity
d. One air mass at 25°F and 10% humidity and adjacent air at 30°F with 70% humidity.
e. One air mass at 60°F and 40% humidity and adjacent air at 40°F with 60% humidity.
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. Which weather “front” condition is most likely to cause flooding?
a. A stationary front that is stalled in one place.
b. An occluded front.
c. A warm front.
d. A cold front.
e. None of the above.
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 an occasional
invasion of “Continental Polar (cP) air mass is more likely to reach Florida than 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. Westerly winds tend to push
everything from west to east, so an invasion of Arctic air moving into the United States will
tend to move more to the east than to the west. 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 along a warm front than along a cold front because warm air
moves faster than cold air
b. are more vigorous with a cold front than with a warm front because cold air
wedges under warm air for rapid lifting
c. will produce little rain or snow 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. A very warm day at the Equator when masses of water and sunshine are storing energy
through evaporation.
b. Sea level air pressure below 900 mb at about 25ºN latitude.
c. Sea level air pressure below 700 mb.
d. Humidity lower than 10% for several days in a row.
e. None 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, which of the following wind
patterns is mostly likely to result?
a. The storm begins with winds from the east, then from the west as the storm leaves the
area.
b. Winds start blowing from the east, then from the south.
c. Winds pick up from the east, then blow from the west as the storm moves out of the area.
d. Winds pick up from the east, then blow from the northwest as the storm moves out of the
area.
e. Winds begin to blow from the west or southwest as the storm develops, then blow from
the northeast or northwest as the storm moves on through the area.
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. Which of the following is true of a “blocking high”?
a. A “blocking high” is a cell of high air pressure that persists longer than usual over a
region.
b. A “blocking high” can prevent a low-pressure system from moving into the area.
c. A “blocking high” can contribute to drought by preventing storms from arriving.
d. A “blocking high” can result in flooding somewhere further away, by preventing a lowpressure system from moving on to somewhere else.
e. All of the above are true.
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. Which of the following conditions is most likely to allow a hurricane to penetrate deeply
into a continental land mass?
a. Very cold air at the surface, and warm, dry air aloft.
b. Trade winds that are very dry.
c. Excessive soil moisture from flooding that occurred during a previous storm.
d. All of the conditions above will strengthen a hurricane as it moves inland.
e. None of the above conditions will support a storm of any kind.
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. An atmospheric trough or depression can lead to a hurricane or other severe
weather because ________.
a. air is heavy with humidity and sinks toward the surface
b. heavy air at the surface spreads out in all directions as strong wind
c. air is converging and lifting
d. high air pressure causes high ocean level, high winds and high waves
e. Answers ‘a’ and ‘b’ and ‘c’ above are 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 storm because it continued to add
new sources of energy as it moved northward into cold 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. Air masses have which of the following characteristics?
a. All air masses are almost always stable, being dominated by cold, dry air.
b. They are most common at high latitudes and are rarely found near the Equator.
c. In the mid-latitudes, air masses sometimes invade other regions, leading to severe
weather.
d. Air masses are created by conditions they encounter after they arrive at some new
location.
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 water molecules begin sticking together to form a liquid.
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 structures
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.