Salt Lake Community College
Geography 1000 – Physical Geography
AJ Allred, Adjunct Fall, 2014
Student Name ____________________________
Quiz 7
With Notes
Students: Even though notes are associated with each question, these notes can be useful for other
questions as well, and are intended to serve as a general study guide.
Notes to Question #1: Hadley cells involve two of the four major types of precipitation: convective and
convergent. Near the Equator, vast ocean water combines with year-round, nearly vertical solar rays to
produce light-weight, humid air that rises easily. These low-pressure patterns result in almost daily
convective rainfall.
The ITCZ is a convergence zone as dry air from north and south moves toward low pressure. During
northern hemisphere summers, the ITCZ tends to be located somewhat further north than the Equator
because the vertical rays of the Sun are further north as well.
So, rainy seasons tend to occur when the ITCZ is nearby. In India, when the ITCZ is to the south, rainy
weather tends toward the south and drought may occur further north. When the ITCZ is overhead, onshore winds bring wet air that result in convective lift and precipitation over land.
Monsoon is a wind effect, but when the ITCZ is a little closer to Arizona in summer, normal high-pressure
systems can draw moisture up from the south and deliver it even as far north as Utah, creating a
‘monsoon’ rainy season in some parts of our state.
When days are short in the United States, the ITCZ is in the southern hemisphere, bringing rainy
conditions there.
Southern Arizona is near the north end of a general Hadley cell. The equator is close to the south end of
Hadley circulation in the northern hemisphere. The convergence of two Hadley cells forms the ITCZ,
which tends to be rainy because air is lifting in a region that is mostly water and receives abundant solar
energy.
1. Which of the following apply to monsoon conditions?
a. The ITCZ belts the Earth near the Equator, and migrates north and south with the Sun's overhead
location in the sky
b. If the ITCZ is not far enough north in June, places like India may experience drought.
c. Even Utah and Arizona can receive a bit of ‘monsoon’ rain when the ITCZ is located relatively
northward during our longest days of the year.
d. The portion of Hadley cells nearest the Equator will tend to be rainy.
e. All of the above are true.
Notes to Question #2: Frontal or “wedge” storms include some of the world’s most vigorous weather.
Warm, wet air that rises easily to form convective storms will tend to rise even faster when cool, dry air is
nearby. The buoyancy of warm, humid air is enhanced when adjacent air is more dense and stable. Even
with vapor-saturated air, freezing conditions are often found near the tops of thunderstorms. The standard
lapse rates used in class discussion will indicate frozen conditions in clouds even when surface
temperatures are very hot. For wet air that tends to be cooler by about 3.0ºF per thousand feet, ice will be
found as low as 24,000 even when ground surface temperatures are 100ºF.
2. When a frontal/wedge storm occurs, a cooler, drier air mass collides with a warmer, more humid air
mass. The result is rapid lifting, gusty winds and precipitation. Lightning, thunder and hail are
common. Even on a hot summer day, a thunderstorm often involves ice because convective cloud
tops can reach extreme altitudes where air is frozen year-round.
True ___
False ___
Notes to Question #3: Evaporation converts sensible heat (heat we can sense or feel) into latent heat that
we can’t usually detect. Energy is not lost; it is converted to a different form. Loss of sensible heat results
in lower measured temperature. That is the energy “price” that is paid in order to convert liquid water into
invisible water vapor. Condensation has the opposite effect of evaporation. Energy that was hidden by
evaporation returns when water vapor converts back to liquid water.
This process is vital to understanding atmospheric instability: when air rises for any reason, condensation
may occur, forming clouds in the sky and releasing latent heat back to heat we can feel and measure as
higher temperature. Unstable air can result as release of latent heat causes air to rise more vigorously,
perhaps releasing more latent heat each time humid air decompresses and cools with rising altitude.
Strong or gusty winds may result, and rapidly rising air can promote formation of hailstones, lightning and
thunder. Trade winds and ocean currents help move tropical heat and humidity to other places.
3. Evaporation is an effective way of absorbing or ‘hiding’ heat so that it can be carried away by
convection. One result is severe storms in places far from the Equator and precipitation that
helps prevent drought in sub-tropical regions. Without hurricanes and other severe storms
Florida would suffer from drought.
True ___
False ___
Notes to Question #4: Utah has plenty of atmospheric heat because abundant sunshine is seldom blocked
by cloud cover. Ordinary thermal heat is measured as temperature, like “cash” in hand. Water vapor
represents a latent, or hidden source of energy for more vigorous storms, like money on an ATM card.
Utah already has enough heat to produce dust devils during warm weather. A tornado is much more
powerful because it contains heat and humidity (evaporated water), which adds a great deal of energy to
air that is already rising due to heat-caused buoyancy.
Hurricanes are normal for “Mother Nature” in Florida. Millions of people living near the beach is not
normal. Americans are gamblers and complainers.
Utah is more likely to have dust devils on a hot day instead of a genuine tornado because hot air cools
rapidly with altitude and there is not much humidity or water vapor available to condense back to liquid
for more heat.
In a sense, a tornado has heat as “cash” and latent heat as “credit”. Cash and credit are needed for severe
weather. The world’s worst weather also needs contrasting cooler, drier air nearby to get even more effect
out of rapidly rising humid air.
4. Utah hosts a few funnel clouds or tornadoes in an average year. To have more tornadoes we need:
a. More water.
b. More heat.
c. More mountains.
d. Closer proximity to the Equator.
e. None of the above will help produce such severe weather.
Notes to Question #5: Arizona is near the north end of a general Hadley cell. The equator is close to the
south end of Hadley circulation in the northern hemisphere. The convergence of two Hadley cells forms
the ITCZ, which tends to be rainy because air is lifting in a region that is mostly water and receives
abundant solar energy.
Florida and Alabama should be dry like Arizona, but they are not because trade winds bring humidity and
rain westward from the Atlantic Ocean to the southeastern United States.
The United States is unusual in that the southeastern states are humid rather than desert-like, even though
they are located under the northern end of Hadley cells where descending, warming air should produce
dryness. Instead, trade winds from the east bring latent heat in moist air.
The undulating jet stream from the west sometimes moves in a more north—south direction, helping to
bring cool, dry air into contact with warm, wet air. The contrast between such air masses creates
relatively greater buoyancy and more vigor in storms.
Mid-latitude cyclones are a unique combination of dry-cool air colliding with warm-humid air.
5. “Tornado Alley” in the United States is a function of: which factors below?
a. The southeast USA is very dry instead of lush and green
b. Westerly winds dry out as they cross the country heading toward the west coast
c. Trade winds that push to the east, creating hot, dry conditions in African Sahara
d. Mid-latitude cyclones that are created at the Equator and move northward to the USA
e. Meridional jet stream flow that helps mix air masses that differ greatly in heat and humidity
Notes to Question #6: The term “cyclones” refers to rising air that, in the northern hemisphere tends to
turn counter-clockwise. Anticyclones tend to exhibit descending air that turns clockwise in the northern
hemisphere.
Cyclones are always about humid, lightweight air that is naturally buoyant. Coriolis force combines with
in-coming convergent winds to result in oddly counter-clockwise flow. Anti-cyclones represent sinking
air that is pushing outward, away from a center or ridge of pressure. Coriolis force turns anti-cyclonic
flow to the right, causing clockwise flow.
Cyclones are always about rising air, turning counter-clockwise. It is also true that “what goes up must
come down” so subsiding air must occur somewhere, sometime, to account for air that was rising with the
cyclone.
6. Cyclonic weather involves wind:
a. moving counter-clockwise with rising air.
b. moving clock-wise with sinking air.
c. moving counter-clockwise with sinking air.
d. that is sinking due to the weight of heavy water vapor
e. All of the above are true
Notes to Question #7: The Earth’s surface accounts for about 45% of all solar energy that the Earth
absorbs (instead of reflecting). Because the lower atmosphere is denser near the surface, more solar
energy is absorbed near the surface than higher in the atmosphere. Together, these effects ensure that
under normal conditions the Earth warms from the surface upward each day.
That condition promotes daily instability, as warming near the surface causes air to rise, which cooler air
aloft tends to sink toward the surface. This cycle occurs daily unless an “inversion” is in place.
Even though it is true that the upper atmosphere receives solar energy first, there is very little absorbing surface
high in the atmosphere, so most solar energy passes through to be absorbed by dirt and water at the surface. Some
radiation is re-radiated from water and dirt and is absorbed by the lower atmosphere.
So, each morning, the earth warms from the surface upward. That means the atmosphere is always unstable,
because warm air at the surface will rise, while cooler air aloft will tend to sink. The cycle repeats daily, unless an
“inversion” is in place.
7. The atmosphere warms mostly from the bottom because:
a. Gravity makes air pressure and atmospheric mass more dense near the surface, providing more substance
for absorbing solar energy
b. Dirt, rock and water at the Earth’s surface absorb much more solar energy than does thin atmosphere
c. The atmospheric ozone layer does warm somewhat as it absorbs ultraviolet energy, but that absorption is
only a small portion of overall Earth warming
d. Most water vapor and liquid water are near the surface, and water easily absorbs and releases energy
e. All of the above are true
Notes to Question #8: Intense heating of land surfaces plays a role in cyclonic, rising air. However, without water
vapor aloft a ‘dust devil’ soon dissipates by rising above its own source of heat at the surface. You might say “cash”
runs out and there is no “ATM card” full of water vapor that contains latent heat.
Dust devils might be 30 feet in diameter and last a few minutes. A genuine tornado could easily reach a diameter
greater than 100 yards and might last 20 minutes of longer. A hurricane often has a diameter of hundreds of miles and
lasts an average of two days, and often much longer.
8. Which of the following statements is FALSE?
a. A dust devil is low-pressure rising air that derives energy from hot surfaces below
b. A tornado derives energy for rising air from energy aloft and differences in buoyancy above
c. A dust devil will subside quickly with time or altitude for lack of water vapor holding latent heat
d. A tornado relies on energy in water vapor and on differences in buoyancy with air nearby
e. An average hurricane is about 10 times larger in diameter than an average tornado
Notes to Question #9: When there is no inversion, air aloft tends to be cooler than air near the surface. Very cold air
has only small capacity to hold water vapor, so high above the Earth there is relatively little latent heat that might be
converted back to liquid water and sensible heat.
Remember, this is not about moving air, just about the difference between air temperature at different elevations.
The adiabatic process is more about how air temperature changes as it is either compressed or decompressed when
lifting or sinking to altitudes that are either higher or lower pressure. Adiabatic is about temperature change by
pressure change. More pressure concentrates energy to produce a higher temperature reading. Lower pressure
disperses energy to exhibit a lower measured temperature.
The fact that the earth warms mostly from the surface upward explains both statements above: Air that warms more at
the surface than high aloft (lapse rate) will also tend to rise and replace cooler air that tends to move downward
(adiabatic).
9. The normal lapse rate of air temperature means that warmth varies inversely with altitude: the higher you
are in the atmosphere, the lower your air temperature. Dry air is especially cold at high altitude because it
contains relatively little latent (hidden) energy storage in the form of humidity (water vapor).
True ___
False ___
For Question #10 see #9 above.
10. Which of the following statements is TRUE?
a. Trade winds push hurricanes toward the east coast of the United States and away from the west coast
b. Hurricanes do not form at the Equator due to lack of air masses of differing temperature and humidity
c. Trade winds are created by high-pressure, sunny weather that pushes air westward parallel to the Equator
d. Extra-tropical storms are a means of transferring heat away from the tropics
e. All of the above are true
Notes to Question #11: Vertical air movement helps separate particles of differing electrical charge. Positively
charged ice tends to collect near the tops of clouds, while water droplets with negative electrical charge concentrate
lower in clouds. The ground surface tends to be positively charged. When enough electrical charge exists, a pathway
opens between the ground or other clouds and energy and a bolt of lightning discharges that energy.
Rapid heating of the air near a lightning bolt causes momentary extreme air pressure, like hitting a drum, and a
relatively slow sound wave travels outward in all directions.
11. Which of the following statements is FALSE?
a. Rapidly rising air in a thunderstorm is like charging a battery
b. Lightning bolts are like discharging a battery of electricity stored in the sky
c. Thunder causes electrical charges to build up in a cloud, leading to a release of lightning
d. Thunder will reach your ears at about 5 seconds per mile slower than lightning reaches your eyes
e. Lightning is a function of energy differences stored in water and ice.
Notes to Question #12: All four of the classic types of precipitation ‘storms’ involves the same essential steps:
-
Air move and absorbs heat and water by evaporation
Air lifts
Air decompresses as it moves into lower air pressure aloft
Air cools by decompression as energy is dispersed or deconcentrated
Clouds of liquid condensation may form if air cools to the point where there is insufficient energy to keep
water in vapor form
Precipitation may fall as rain or snow (or sleet, etc.)
Loss of water from the air results in drier, less buoyant air that tends to sink (or go down the mountain)
Sinking air tends to warm by compression. Energy has not been gained, only concentrated to show higher
measured temperature
At the bottom of the mountain air will often be more dry than before it lifted over the mountain. Some water
was left on the mountain in the form of precipitation
A “swamp cooler” takes advantage of the energy in hot outdoor air by using it to evaporate liquid water into
vapor that holds latent heat in humidity. Swamp coolers are economical but provide only limited cooling effect
and indoor humidity can sometimes be a problem.
“Central Air” is also known as refrigeration cooling. This expensive process involves the adiabatic effect of
changing air temperature by compression and decompression. Heat is extracted from very hot compressed air
using fluids. Then, allowing that air to decompress results in very cold air at any desired temperature.
A “blow dryer” is like a swamp cooler – hot air has great capacity to hold water. Some people actually feel cooler
while using a “blow dryer” because so much evaporation is taking place.
12. Which of the following is false:
a. Air blowing over a high mountain should be more humid after it descends to the bottom on the other side. .
b. Energy cannot be destroyed, but it can be hidden when it evaporates liquids into vapor. It takes energy to
turn liquid into vapor, but the energy is not lost, nor is the liquid destroyed. They are just hidden (latent)
c. A ‘swamp cooler’ (evaporative cooler) converts heat into humidity. Heat and water are ‘hidden’ in the air
d. The energy absorbed during evaporation is stored as vapor, making the air feel cooler. The air also
becomes more humid.
e. Compared to evaporative cooling, refrigeration (compression/expansion cooling or central air) is
expensive. The first step squeezes air to concentrate heat. After blowing off that concentrated heat, the air
is allowed to decompress, resulting in very cold air.
f. An electric hair dryer is basically an evaporative cooler: heat is used to evaporate water.
Notes to Question #13: For class discussion, we break the normal environmental lapse rate into two parts: very dry
air is assumed to be cooler with altitude at an average rate of about 5.0 degrees per thousand feet; while vaporsaturated air retains relatively more warmth by altitude, and is cooler by a rate of about 3.0 degrees per thousand feet
of altitude.
Humid air contains latent heat that can be converted back to sensible heat we can feel, so on average humid air cools
more slowly with increasing altitude, compared to dry air that has no hidden storage of heat or energy in vapor.
13. Based on class discussion, which of the following statements is not true?
a. In perfectly dry air, the temperature at 10,000 feet should be 50°F cooler than air at the surface
b. In perfectly wet air, a ground temperature of 100°F corresponds to a temperature of 91°F at 3,000 feet
above that surface.
c. Air at an altitude of 20,000 feet should be at least 100°F colder than at the surface below.
d. During a weather inversion, air at the surface will tend to be warmer than air aloft
e. Air that is warm and humid will tend to rise, especially because it will be lifting into air aloft that is colder
by reason of lower air pressure and less heating surface area.
Notes to Question #14: The tropics would be very hot were it not for abundant ocean water that absorbs solar energy.
In addition, warm water evaporates easily, which hides vast amounts of solar energy in latent heat (like a giant swamp
cooler). When water vapor converts back to liquid water, clouds form and latent heat is released for warming.
Meanwhile, clouds reflect a large amount of solar energy back into outer space.
Water that has been vaporized can move great distances by air currents. In a sense, energy is transferred from the
tropics by “air mail.”
Taken together, the presence of large water bodies helps ensure that climates are milder than dry regions. Solar
energy is absorbed, converted and transported, helping ensure that the tropics have mild overall annual seasons and
daily weather.
14. In the tropics, ocean water covers most of the surface and is exposed to abundant sunshine. The result is
that ocean water “takes the heat” for us. For even more cooling, solar energy evaporate water and then
transfers that latent heat by wind to far places. Meanwhile, ocean currents carry vast amounts of heat
energy. The latent (hidden) heat in humidity can produce violent storms when that latent heat is released
through condensation. Evaporation is the process of storing heat; condensation is the process is bringing
the heat back when vapor condenses back to liquid.
True ___
False ___
Notes to Question #15: Storm surge during a hurricane or tropical storm can cause severe flooding. Drowning is the
most common cause of death during such storms. Low atmospheric pressure means that the weight of air is not
pushing down on the ocean with as much pressure, so ocean level can rise, just as fluid is drawn up a drinking straw.
Low air pressure from rising air encourages converging wind that can be damaging. Such wind can also drive high
waves that cause additional damage. Storm surge also includes flooding from heavy rain. The combination of all of
these factors causes coastal areas to flood or inundate with a combination of sea water driven inland and rainfall
flooding downstream.
15. Which of the following is NOT true of storm surge during a hurricane or other severe storm?
a. Ocean sea level ‘bulges’ upward several feet as if water were being draw through a drinking straw
b. High winds drive that bulge of water inland, causing flooding that can move upstream
c. Heavy rainfall can cause flooding that moves downstream
d. Unusually high air pressure combines with high wind and high waves to cause hazard to people and
property
e. High wind can cause widespread damage to buildings, vehicles and trees