Salt Lake Community College – Meteorology 1010
Quiz #4
AJ Allred, Adjunct
Student Name: ____________________
ANSWERS
1. What latitude zone(s) produce(s) conditions that can erupt into violent frontal/wedge storms?
a. Polar
b. Sub-tropical (‘B’ climate zone only)
c. Tropical
d. Mid-latitude
e. All of the above
Polar regions can exhibit high winds and very cold temperatures, but lack enough contrast in heat and
humidity between air masses to produce serious frontal storms.
Dry sub-tropical areas may contain enough heat, but not enough moisture (latent heat) to produce genuine
frontal conditions very often. Instead, dry and desert areas are more likely to exhibit wind storms and
simple air-mass thunderstorms.
Tropical regions have vast amounts of atmospheric heat and humidity, sufficient to produce tremendous
rainfall, and some lightning and high wind; however, without much Coriolis effect and contrasting
cooler/drier air nearby, there is no real tornadic development that leads to tornadoes and other truly severe
weather events.
Mid-latitudes are the ideal place for combat between invading air masses from the north or south. The
south-central United States is low, flat, humid country that is perfect for invasion of warm/humid air from
the gulf and Atlantic. Likewise, cooler/drier air from Canada can easily invade as well. When these very
different air masses collide, rapid rising buoyant air can draw in severe winds. When combined with
Coriolis force, violent frontal weather can result.
2. High winds in the Salt Lake area on Thursday, November 22, were caused by a cold front that
brought precipitation and clouds with humidity.
True ___
False _X__
High winds last week were from a brief high-pressure system of cold, dry air that invaded from the east.
Cold, dry air is not as likely to bring precipitation as the warmer/wetter air that typically brings storms
from the west and southwest.
In fact, the easterly high winds caused damage on the ground but brought no precipitation. Instead, brief
low-pressure systems from the west occurred just before and just after easterly flow. Those small, but
genuine storms did bring some precipitation into Salt Lake Valley. The high-pressure system from
Wyoming was only about wind.
3. As a rain storm finishes passing directly over the Salt Lake valley, which of the following
phenomena is most likely to occur:
a. More precipitation occurs in Davis County than in most of Salt Lake Valley
b. Winds from the southwest
c. Winds from the east
d. Answers ‘b’ and ‘c’ are best
e. None of the above is a good answer
This question requires careful thought. When a storm first arrives in our area, we tend to feel wind from
the southwest, the front—right part of the storm. As the storm passes by, two things happen:
1. The back side of the storm brings winds from the west or northwest.
2. These winds may pass over the Great Salt Lake (to the west) and pick up moisture that is then
deposited on Davis County downwind (east) of the lake.
So, genuine storms (precipitation, wind, cloudiness, etc.) arrive in Utah from the west and southwest.
Only rarely do we get a flow of moisture from the east that brings precipitation.
4. In the northern hemisphere, Hadley cells produce lush rain forest on the north end and dry or
even desert conditions at the south end. That is why St. George and most of Utah are dry.
True ___
False _X__
In the northern hemisphere, the south end of a Hadley cell is near the equator, where wet and warm
conditions prevail. The north end of that Hadley cell provides dry, descending air that is typical of
deserts.
In the southern hemisphere, the opposite occurs. The far south end of a Hadley hosts dry country while
the north ends meets at the ITCZ near the equator.
Most of Utah is dry because we are close to the dry north end of a Hadley cell that continues on down to
the humid, rainy equator (ITCZ).
5. What air mass combination below is best for inducing a violent frontal storm?
a. 75°F / 40% humidity moving into an area of 85°F /90% humidity
b. 65°F / 50% humidity moving into an area of 60°F /75% humidity
c. 85°F / 50% humidity moving into an area of 80°F /55% humidity
d. 75°F / 40% humidity moving into an area of 95°F /35% humidity
e. 35°F / 40% humidity moving into an area of 45°F /50% humidity
Answer ‘a’ is a very good combination for violent weather: both air masses have plenty of heat energy and
the cooler mass is also much drier than the warmer air mass. A temperature of 85°F and very high
humidity is ripe for a severe thunderstorm.
Answers ‘b’ and ‘c’ represent air masses that are not very much different from each other, so both might
rise together, possibly producing thunderstorms but probably not much more.
Answer ‘d’ is similar but not nearly as severe, because the warmer air mass is actually quite dry. That
mass cannot sustain long-lasting rising air because it contains relatively little latent heat in vapor
(humidity).
Answer ‘e’ is just too cold and dry to produce violent weather.
6. In a winter weather inversion, which factor is unusually weak or inactive?
a. Morning or valley breeze
b. Canyon or mountain breeze
c. Cold air descending at night
d. Long nights with heavy outbound surface radiation
e. Overcast days and/or clear nights
An inversion condition involves stable (stale) or descending air. The usual morning surface heating that
produces an uphill valley breeze is not present. Such conditions are typical in winter, when valleys are
shaded and cold. Lake of daily warmth at the surface prevents the cleansing of rising air that moves
pollutants away.
Instead, the evening downhill mountain breeze brings yet more cold air. As the pattern continues, air aloft
is typically cleaner and warmer than air trapped at the surface.
Long nights with lots of out-bound radiation help cool the surface even more, leading to yet more dull,
stale and stagnant air that further collects pollutants.
Overcast conditions and heavy haze add further to the inability of lower surfaces to warm up enough to
create rising air that might remove air pollution.
7. If the ITCZ fails to follow the sun from March through June, what is most likely to occur:
a. Southern Utah is likely to experience unusually heavy summer rainfall and some flooding
b. People in India will experience a drought
c. There will be no dry season in the northern edge of the tropics
d. “monsoon” condition is mostly about wind. Precipitation is not involved
e. All of the above are true
This is a difficult question.
During Spring in the northern hemisphere, the sun move northward to its high point in the sky on June 20.
The ITCZ tends to migrate north and south with the sun. In normal years the ITCZ, with its converging
air masses and precipitation, will tend to be more in the north as well. So, places like southern Utah ought
to have more precipitation as it is located not far from the summer northern end of the ITCZ. Sometimes
we call that the “Arizona monsoon” even though ‘monsoon’ is more about wind. Wind does affect
precipitation.
Meanwhile, south of the equator ought to be drier than usual, because the ITCZ is somewhere above the
equator and the dry end of the Hadley cell has moved northward toward where the ITCZ was earlier.
It the process above fails to happen, then the ITCZ stays southerly. Doing so means that drought may
occur north of that area and the rainy season is longer in the southern side of the equator. India and Utah
are in the northern hemisphere, so having the ITCZ relatively far away should mean less precipitation in
those areas.
Meanwhile, near the equator there may be persistent rain because the ITCZ did not move northward
enough to let dry conditions take over for a season.
8. Northern hemisphere ‘jet streams’ result from the Coriolis effect counter-acting rightward
against the pressure gradient that normally flows from the Equator toward the North pole.
True _X__
False ___
World-wide, a general atmospheric pressure gradient pushes northward from the equator. The Coriolis
force tends to deflect or bend wind to the right, which eventually results in wind from the west to the east.
The high-speed portion of this eastward flow is known as a jet stream.
9. Dust devils exhibit all of the same features as tornadoes, and differ only in size.
True ___
False _X__
Dust devils and tornadoes have much in common: rising warm air spiraling inward toward the center of
low pressure.
However, a major difference is that a genuine tornado is associated with humid warm air that contains vast
amounts of latent (hidden) heat in water vapor. As this humid air rises, decompresses and condenses-out
humidity into visible liquid water, a tremendous amount of heat is released to encourage more rapidly
rising air.
So, a dust devil tends to die out with altitude as it loses its dry heat source near the ground surface. In
contrast, a genuine tornado can rise as long as the air contains sufficient humidity to keep re-warming
itself by condensing vapor back into liquid water.
Genuine tornadoes also tend to be much larger than simple dust devils, because tornadoes contain much
more energy than just hot air.
.
10. An idealized world model based only on Hadley cells would call for Georgia and Alabama to
have a climate like Arizona.
True _X__
False ___
Regions at roughly 30°N and 30°S are at the far end of Hadley cells that derive their air movement from
rising humid air at the ITCZ that centers over the equator. With humid, rising air near the equator the
opposite end will tend to exhibit dry, descending air. The result is dry climates or even deserts over places
like Arizona.
Georgia and Alabama ought to be dry as well, being located near the north end of Hadley cell movement
however, because of westward-moving trade winds that bring moisture to North America, the southeast
United States is humid and cooler than Arizona.
11. Salt Lake City can experience orographic, convective and frontal precipitation on the same day.
True _X__
False ___
Because of mountains and dry climate, Salt Lake City experiences frequent orographic, or mountain-effect
precipitation. We also experience frequent weather fronts arriving from the west. In warm weather,
surface heating and relatively high humidity can set off brief air-mass thunderstorms (convective).
On occasion, with enough heat and humidity available, we can also get frontal or wedge conditions on a
similar, but smaller scale than storms often seen in the U.S. Midwest and southeast. Each year, a small
number of funnel clouds and/or tornadoes are reported or suspected in Utah.
12. How would Utah’s general climate categories change if a long-term or permanent “El Niño”
condition were in effect?
a. Utah’s dry (D) climate would give way to a more humid/rainy ‘B’ climate
b. Utah’s “H” condition prevents any real change in climate, regardless of a permanent “El Niño”.
c. Utah’s ‘B’ climate would become more of a ‘D’ climate in the north and ‘C’ in the south
d. Utah’s ‘H’ climate zone would become significantly more ‘C’ or even ‘A’
e. Utah’s prevailing ‘E’ climate would gradually convert to ‘A’ or even ‘B’
We have a ‘B’ (dry) climate, with some ‘H’ (highland) climate. An El Niño condition tends to bring
more precipitation for a season. If that wetter condition were to become permanent, then our climate
zone would probably be labeled ‘D’ (severe continental) in the colder northern part of Utah, and ‘C’
(mild continental) in the warmer southern part of the state.
13. The passage of a tropical storm will typically exhibit a change in atmospheric pressure of about:
a. +10mb
b. -50mb
c. -205mb
d. +250mb
e. Plus or minus about 507mb
Answer ‘a’ is an increase in air pressure, the opposite of what normally occurs with storminess (rising air).
Answers ‘c’, ‘d’ and ‘e’ represent almost impossibly severe changes in air pressure.
Answer ‘b’ represents a drop in air temperature consistent with a change from sunny weather to a
substantial storm, such as an air-mass thunderstorm or even a tropical depression with high winds and
heavy precipitation.
14. Anti-cyclonic conditions may exhibit all of the following except:
a. Clockwise movement of air
b. Rising air
c. High wind
d. Slow descending masses of dry air and/or atmospheric stagnation
e. A tendency for fair skies but haze and/or air pollution as well
Anti-cyclones are the opposite of tornadic or cyclonic air flow that is associated with storminess. High
atmospheric pressure is associated with stability, or even downdrafts. High-pressure conditions are
associated with fair skies that often include build-up of haze and stale, polluted air.
Air flow from a high-pressure cell will tend to spiral downward and outward in a clockwise or ‘anticyclonic’ manner, the opposite of a low-pressure system.
On occasion, high air pressure can result in high winds, especially when a low-pressure cell is not far
away. Cool, dry air is relatively dense or heavy and can pick up real speed when flowing outward and
downhill from high places such as Wyoming. Another example is the Santa Ana wind that involves highpressure in Arizona flowing downhill toward the California coast, resulting in high, dry winds that can
make wild fires worse.
15. In climate terms, a ‘positive relationship’ between variables or weather phenomena will tend to
help preserve good weather and prevent severe storms and climate change. In contrast, a
‘negative’ relationship between variables tends to result in climate disruption, severe weather
and unpredictable climates in the future.
True ___
False _X__
A positive correlation or relationship indicates that two variables are moving in the same direction. Positive
relationships tend to make things more severe, or get out of control.
In contrast, negative relationships tend to be self-cancelling. An increase in one variable causes a different variable
to counter-act or oppose the first variable.
A “positive feedback” situation is self-reinforcing: the more it occurs the more it will tend to occur again.
Relatively stable earth climate and weather patterns can be severely disrupted if a self-reinforcing condition occurs.
For instance, if warming air melts polar ice, then dark ocean surface will increase, allowing even more solar energy
to be absorbed, and further warm the atmosphere. Further warmth melts more ice at an increasing rate, reinforcing
the original change. Eventually, all ice may melt, leaving dark ocean to absorb vastly more solar energy and warm
to the point where a new condition dominates.
16. The magnitude of a tornado is based on the height of the funnel cloud and how long it was on the
ground. Tornadoes that reach the Earth’s surface for more than 1.0 hour typically rank close to
1.0 on the Enhanced Fujita (EF) scale.
True ___
False _X__
The magnitude of a tornado is not based on the height of the funnel cloud, nor based on how long the funnel is on
the ground. Instead, we use the ‘Enhanced Fujita’ (EF) scale that is based on estimated wind speed inside the
tornado.
Most tornadoes last only a few minutes. Some very large tornadoes can last for closer to an hour. Tornadoes with
the strongest wind speeds tend to rank 4 or even 5 on the EF scale. A tornado measuring EF 1.0 is a relatively small
tornado.
17. What air pollutant is most likely to cause air quality alerts in Salt Lake valley:
a. ozone
b. methane
c. CFC
d. particulates
e. “NOX” and “SOX”
Small amounts of ground-level ozone are caused by natural conditions such as lightning or ocean waves. Most
ground-level ozone is created by sunlight interacting with human-caused air pollution such as oxides of nitrogen
and sulfur. Together, these are called “photo-chemical smog”. So, ground-level ozone pollution is mostly a human
process.
Warm sunny days with large amounts of urban air pollution give rise to Utah’s most common air alert condition
simply because of that “photo-chemical” process. Humans add oxides to the air, and sunlight reacts to that by
producing ozone near the ground.
In cold weather the most serious air pollution condition is caused by atmospheric temperature inversions, when
surface air is colder than air aloft. With cold air below and warm air above, there is no reason for surface air to rise
and clear-out local ground-level air pollution.
Keep in mind that atmospheric ozone (the ozone layer) is a very different phenomenon, having little to do with
ground-level ozone. We need atmospheric ozone (located high in the stratosphere), to absorb dangerous ultraviolet
solar energy. Synthetic chemicals like CFCs tend to migrate into the stratosphere where they greatly diminish
natural atmospheric ozone that would otherwise block unwanted ultraviolet rays.
So, the key to ozone is location, location, location. Stratospheric ozone is helpful; ground-level ozone is not.
18. Aside from human activities, the earth’s climates have been continually changing over millions of years,
in part due to:
a. Changes in electromagnetic energy sent to earth by the Sun
b. Tectonic forces, including massive volcanoes
c. Changes in earth rotation, axial wobble and polar axis tilt
d. Strikes by large, fast-moving meteorites
e. All of the above alter Earth climates over time
The answer is in the optional answers above. All are true.
19. The frequency of Doppler radar return pulses will slow down as the target object gets closer to a radar
station because each radar pulse does not have as far to travel to and from the station.
True ___
False _X__
The opposite is true. As an object moves further from a radar station, it takes longer for a radar pulse to reflect or
bounce off the object and get back to the station. So, the average time between pulses gets longer and longer the
further the reflected object moves away from the radar sender.
For objects that are moving closer to the radar station, each reflected pulse gets back to the sending station quicker,
so that the pulse frequency is a rising tone.
Doppler radar cannot detect a tornado directly, because wind is not a good radar reflector. Instead, Doppler radar
can be used to detect the rain or snow being blown tornadically.
When the difference in pulse rate is much faster in one area than another, a tornadic condition may be occurring and
an alarm or warning may be issued. Doppler radar can work at night or through heavy cloud cover.
20. Climate change can be detected by which of the following?
a. Everything below
b. Sea floor and lake sediments
c. Tree rings and coal beds
d. Fossils and wine production records
e. Rocks and polar ice
The answer is in the optional answers. All are true, along with many other causes that are not listed above.
21. Current Utah news reports that the most important concerns of Utah residents are:
a. Jobs and education
b. Air quality, with ozone problems in the winter and particulate pollution in the summer
c. Crime and Jobs
d. Air quality, with ozone problems in the summer and particulate problems in the winter
e. All of the issues above rank #1 in Utah
Air quality is becoming a serious issue along the Wasatch Front. The outlook is for more people and much more air
pollution. The local “air shed” simply does not have the capacity to deal with so many people who love to drive.
Industrial sources of air pollution are also important, but less so than automobiles.
22. Utah’s dry climate is particularly prone to high soil acid and acid rain, especially compared to the eastern
United States where high humidity creates more problems with alkalinity and low pH (10-14).
True ___
False _X__
The opposite is true. Utah’s dry climate tends to promote alkaline soils (also called ‘basic’). Acid conditions are
more common in humid regions.
However, Utah air pollution, including the burning of coal for electricity generation, contributes substantially to
atmospheric acidity, especially since the wind blows from Utah to places in the eastern United States that are much
more vulnerable to soil, water and atmospheric acidity. Acid rain is a world-wide problem, leading to crop failure,
deterioration of structures and destruction of forests.
Human activity, especially the burning of fossil fuels, tends to make even the oceans more acidic, by absorption of
carbon dioxide into ocean water.
In any case, a pH of 10-14 is very alkaline, not acid.
23. What is the difference between a pH of 4.0 and a pH of 7.0?
a. pH 4.0 is 3.0 times more acid
b. pH 7.0 is 1000 times more basic or alkaline
c. pH 7.0 is 30 times more alkaline
d. pH 7.0 is 300 times more acid
e. pH 4.0 is 30% more acid than 7.0
Each whole number change in pH represents a change of 10x or ten times. So, a change from 4.0 to 5.0 represents
10 times more alkalinity. A change from 7.0 to 5.0 represents a change of 10 x 10, or 100 times more acidity. So, a
change from 4.0 to 7.0 represents an increase in alkalinity of 10 x 10 x 10 = 1,000 times.
24. A climograph with a strong dip in the middle represents a climate zone located somewhere:
a. South of the equator
b. North of the equator
c. At a seaport near the equator
d. A place near a large body of warm water
e. Answers ‘a’ and ‘b’ are best
A climograph shows 12 months of long-term average weather conditions for a geographic location, for precipitation
and air temperature. The graph begins with January and ends with December, so a dip in the middle indicates that
the selected location has its lowest average monthly temperature in June-July. Such places tend to be south of the
equator where annual temperature differences are the opposite of the northern hemisphere. South of the equator, the
warmest months (summer), occurs in December and January, the opposite of places in the northern hemisphere such
as the United States.
A seaport would be located at sea level and obviously near substantial water that creates a milder climate. So,
typically a sea port climograph would show no strong dip in the middle because ocean water releases heat during
the winter that it was absorbing all summer.
25. Typically, an “El Niño” condition means that, once every several years, trade winds pull Pacific
ocean water westward less vigorously or not at all. So, the normal build-up of warm ocean
water and storms in the far western Pacific region is reduced for a season.
True _X__
False ___
The statement above is true in general. The result is generally that a lack of warm water in the western Pacific
reduces the likelihood of severe storms and heavy precipitation. At the same time, some dry places on earth, such
as the southwest United States, may get more-than-usual precipitation, sometimes causing persistent flooding for a
season.
A “La Niña” condition is roughly the opposite of an El Niño season: some dry places may be extra-dry for
a season and storms in the western Pacific may be even worse than usual.
Of course, this answer is very generalized and the ENSO “Niño” phenomenon is complex and not yet well
understood.