Geography 1700 – Natural Hazards
AJ Allred, Adjunct
Fall, 2015
Quiz 13 Explanations
As always, these notes are not intended to be complete, nor replace your own notes from
class. The eTextbook is the most complete source of information for topics that are
important to Geography 1700. Class notes do contain some of the nuances that we bring
into the classroom from current news stories and historical examples of geographic
phenomena that are especially relevant to life in Utah. These same nuances are valuable
to the extent that they are also broadly applicable around the world.
Question 1
A cumulonimbus thunderstorm cloud in Nebraska can potentially reach an altitude of _______________
feet.
almost 10,000
a little less than 30,000
more than 40,000
more than 90,000
Consider that ordinary, half-hour thunderstorms in Utah can reach above 20,000 feet, as moist, warm air
rises easily. However, much of the moisture that moves with the westerlies tends to be lost along the
way, so Utah is relatively dry. Cyclonic storms moving from dry, western states to central and eastern
states may intensify as they receive new moisture after leaving the west.
The eTextbook describes how a severe thunderstorm, including meso cyclones and “super cells” can
over-shoot the troposphere, reaching more than 10 miles into the atmosphere.
Question 2
Doppler radar can detect __________________.
clear air moving at high speed
air that is hotter than 80 degrees F
air that is colder than -20 degrees F
dust, ice and parts of buildings thrown into the air
All of the above
Air is pretty much invisible to radar. Solid objects can often be detected, so wind patterns can be
deduced by tracking the movement of solids carried in the air. A tornado, often embedded in a
thunderstorm, may be impossible to see with our eyes, especially at night; however, radar that uses the
Doppler effect, can detected organized patterns of wind that are moving toward the radar set, or away.
These pairs of air flow can be deduced to represent parts of a tornadic flow.
Question 3
A "micro burst" ______________.
represents the fastest-rising air inside a tornado
air that rises with the help of gravity
is too small to affect people and buildings on the ground
is relatively cooler, drier air than in other parts of a storm
All of the above help describe a "micro burst"
Convective and frontal storms involve release of latent heat as rising air cools to condensation. In
extreme cases, rising air can be very fast, inducing even faster winds along the surface.
Of course, what goes up tends to come down, so downdrafts (gust front, out-flow boundary, etc.) can also
produce high-speed wind near the surface, especially because such as is cooler and drier, and is aided
by gravity in gathering speed during descent. Downdrafts cannot go into the dirt, so they spread out
along the surface, sometimes causing real damage to property and hazard to people.
Question 4
Launching missiles into orbit from Florida is a good idea because ________________________.
the Earth spins faster in Florida than at the Equator
weather in Florida is always mild and calm
lightning, hail, high winds and storm surge are not problems
hot, humid air in severe storms help rockets lift faster into space
None of the above explain why the USA launches "space shots" from Florida.
Geography 1700 integrates topics across a variety of science disciplines. You may recall from early in
the semester that Earth speed of rotation is greatest at the Equator, so launching a missile in the same
direction that Earth turns can provide a speed advantage. Florida and southern California provide
substantial advantage as well, even though they are somewhat north of the Equator.
That general advantage does not prevent Florida from having severe weather. Florida can experience
freezing air, lightning, high winds, storm surge, tornadoes, hurricanes and other weather phenomena. On
an icy day, preparations for space launch can be compromised, as in the case of the space shuttle
Challenger, wherein solid fuel boosters did not assemble correctly due to unusually cold weather.
Question 5
Based on class discussion, recent hurricane Patricia moving onto dry land in Mexico is conceptually
consistent with the possibility that trade winds were not flowing westward in the usual way.
True
False
We accept that El Nino seasons tend to exhibit weak or reversed trade wind flow. We also noted that
Hurricane Patricia turned back to Mexico, rather than continue westward into the Pacific Ocean. Without
knowing all the details, but looking for general patterns, we can reasonably note the apparent association
between trade wind flow and El Nino, and Patricia’s unusual track back to the east.
Question 6
A "dust devil" is weaker than a genuine tornado because ________________.
Utah never has enough humidity to produce a genuine tornado
Utah is too hot for tornado formation
air aloft lacks latent heat
air aloft contains too much latent heat
dust devils always rotate clockwise due to rapidly sinking air
Dust devils are more common in Utah than are tornadoes. Tornadoes and dust devils can both lift dirt
and other debris into the air. Utah is dry, but we sometimes have enough moisture to provoke a genuine
tornado. One key to understanding a genuine tornado is the ability of moist air aloft to release latent heat
during decompression cooling, adding energy for more lifting from the surface. In contrast, dust devils
rely on surface heating, which tends to deplete with altitude. So, dust devils are relatively smaller and
weaker than tornadoes. Many more factors also affect these two types of whirlwinds, but difference in
moisture is a major factor in how powerful these wind patterns become.
Question 7
A storm passing through the Salt Lake area will often exhibit _____________.
winds from the southwest that later come from the northeast
winds from east that later come from the west
winds from the east that create "lake effect" precipitation in Davis County and Park City
All of the above.
None of the above.
By viewing a northern hemisphere mid-latitude cyclone from above, we can see that movement toward
the east will often tend to exhibit winds from the southwest as the storm enters Salt Lake valley. As the
cyclonic pattern leaves our area, the back side of that same counter-clockwise flow will bring winds
moving from the opposite direction.
“Lake effect” precipitation involves evaporation of water from a lake that is later dropped as precipitation
over drier, cooler land. Davis County and even Park City can receive rain or snow that originated as
water evaporated from the Great Salt Lake. The overall direction of winds in most of our local storms is
from west to east, and the Great Salt Lake is west of us. We are “down wind” so lake effects can reach
much of the Wasatch Front. Davis County is closest to the lake and most often affected.
Question 8
A "dry line" storm _______________.
lacks moisture for rain, snow or hail
exhibits a sharp boundary between air masses that differ greatly in moisture content
may occur in Utah and Nevada, but not in Nebraska, Kansas or Oklahoma
can produce dust devils, but not tornadoes
All of the above.
Mid-latitude cyclones involve collision between air masses that differ greatly in humidity, and sometimes
in temperature as well. Warmer, wetter air will rise relatively faster, with higher wind speeds, when drier,
cooler air wedges underneath. The sharper the difference in dryness between air masses, the more
potential for a sharp boundary of severe lifting, with consequence high winds, lightning, precipitation and
other effects. Dry-line storms are not dry, then are just high-contrast. Relatively dry continental/tropical
air cT, can be closely involved, as well as the usual westerly flow of air that dried out as it moved from the
west coast across mountains where orographic storms removed much of its moisture. Relative dryness
sets the stage for severe contrast in the central USA.
Question 9
The U.S. space shuttle Challenger was destroyed because ________________.
of a severe storm in Florida
Coriolis force was suddenly absent during the launch process
humidity was not high enough
of unusually cold air
All of the above are direct causes of the disaster.
Florida contains some tropical climate, but ice is always a potential hazard due to Florida being physically
connected to the central United States, Canada and so on. Failure of solid fuel boosters to seal properly,
due to cold weather, led to booster failure.
Question 10
Convective air movement can occur _______________.
in your kitchen
at the scale of your neighborhood
at the scale of Utah
on the scale of a Hadley cell that spans thousands of miles
All of the above
Rising air can occur on a micro, meso and macro scale. A pot on the stove in your kitchen produces
convective lifting of humid, warm air that may cool, condense and sink along a cold window nearby.
That basic flow occurs within thunderstorms that are more than a mile wide, and regionally across
hundreds of square miles. Finally, Hadley cell flow exhibits this same basic pattern across thousands of
miles.