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ATS 351, Spring 2009
Week 12, Lab #9 – due April 15/16th
Ocean & Atmosphere General Circulation;
Fronts & Cyclones – 58 points
Question #1: Single-Cell Model & General Circulation (8 points)
To compensate for the surplus and deficit of radiation in different regions of the
globe, the atmospheric winds and ocean currents redistribute the energy equally around
the earth. If we make the following assumptions about Earth: (1) The earth’s surface is
uniformly covered in water, (2) The sun is always directly over the equator, and (3) the
earth does not rotate, we can construct a simple model (Single Cell Model) of the
atmosphere’s general circulation. For the following questions, the answer is either at
the poles or at the equator.
(a) Where is the warmest air found?
(b) Where is the highest surface pressure found?
(c) Where would you expect rising air?
(d) Where would you expect sinking air?
Question #2: Three-Cell Model & General Circulation (14 points)
Below is the three-cell model of the Earth’s general circulation.
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a) (6 points) Identify each of the meteorological features by correctly associating
the letter with the features listed below.
Equatorial low:
Northeast trade winds:
Westerlies:
Polar front:
Southeast trade winds:
Polar easterlies:
b) (3 points) Referring to the figure above, how many cells (in the Northern
Hemisphere) do you see? Please label (by correct name) the cells on the diagram
above.
c) (5 points) Using the global precipitation distribution map below, explain why
there is a large amount of annual precipitation over the equator but low amounts
in the subtropics.
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Question #3: El Nino/La Nina (12 points)
a) (6 points) Describe the conditions in the Pacific Ocean during an El Nino event.
How do these differ during a La Nina event?
b) (6 points) What type of weather (cold/warm, wet/dry) would you expect over
North America during a strong El Nino? During a strong La Nina?
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Question #4: Air Masses (8 points)
What type of air mass (cP/cA, mP, mT, or cT) would be responsible for the
weather conditions listed as follows?
a) Hot and dry weather
b) Heavy snow showers and low temperatures at Buffalo, NY
c) Hot, muggy summer weather in the Midwest and the East
d) Record low winter temperatures in South Dakota
e) Daily afternoon thunderstorms along the Gulf Coast
f) Heavy snow showers along the western slope of the Rockies
g) Refreshing, dry breezes after a long summer hot spell on the Central Plains
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h) Warm and moist weather
i) Persistent cold, damp weather with drizzle along the East Coast
Question #5: Mid-latitude Cyclones (10 points)
Describe the process of how a mid-latitude cyclone develops, becomes mature,
and then becomes occluded (drawing pictures will help explain). Which stage the storm
system is most intense? What makes the storm system die? How long do these systems
usually last?
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Question #6: Fronts (6 points)
Use the SLP map shown below to answer the following questions about the
pictured mid-latitude cyclone.
a) Using the isobar analysis (red lines, mb), does the center of the above cyclone
have a relatively high or low-pressure center compared to the surrounding
environment?
b) A cold front is the boundary between the cold, dry cP air and warm, moist mT air.
There is also usually a clear wind shift (change in wind direction) and a
significant (~ 10°F) temperature change at this boundaryIf there is a cold front
associated with the mid-latitude cyclone, label this cold front on the above map
using the appropriate symbol.
c) A warm front is the boundary between the warm, moist mT air and the cooler,
moist mP air. There is usually a slight wind shift at this boundary as well. If there
is a warm front associated with the mid-latitude cyclone, label this warm front on
the above map using the appropriate symbol.
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