Chapter 8: Weather
Where do cA air-masses originate?
Arctic basin and Greenland ice cap
Which of the following air masses probably has the lowest water vapor content? A) cE B) cT C) cP D) cA
D) cA
The coldest and driest winter air-mass in North America is the
cA
An air mass can not be modified when moving across country. (t/f)
false
A nor'easter typically occurs when: A) NE winds associated with a low-pressure system draw mP air into the northeastern United States. B) the polar jet stream weakens and allows mP air to invade New England. C) the NE tradewinds strengthen in the Pacific during a La Niña event. D) a cP air mass from the northeast moves into Texas.
A) NE winds associated with a low-pressure system draw mP air into the northeastern United States.
Which air mass does not usually influence weather in the United States during the summer? A) cA B) cP C) cT D) mP
A) cA
Which of the following is NOT an air mass that influences North America? A) mA B) cP C) mT D) cA E) mP
A) mA
What is an atmospheric river?
An atmospheric flow that transports vast amounts of moisture to regions outside of the tropics.
Which of the following statements is TRUE of lake-effect snowfall? A) Lake-effect snowfall accounts for only a small portion of seasonal snowfall along the eastern edges of the Great Lakes. B) Along the Great Lakes, lake-effect snowfall usually only occurs within 80 km of the leeward lake shores. C) Lake-effect events are not capable of generating more than a centimeter or two of snow. D) Lake-effect events are produced through the modification of mP air masses.
B) Along the Great Lakes, lake-effect snowfall usually only occurs within 80 km of the leeward lake shores.
Air-mass source regions are LEAST likely to exist in: A) subtropical regions. B) middle-latitude regions. C) equatorial regions. D) polar regions.
B) middle-latitude regions.
While on vacation in Florida, you experience several days of weather with maximum temperatures of 90°F and dew points above 65°F. What educated guess could you make about the weather? A) It is caused by an mP air mass. B) It is caused by a cT air mass. C) It is caused by an mT air mass. D) It is not air mass weather.
C) It is caused by an mT air mass.
Which one of the following conditions would enhance the development of a lake effect storm? A) moisture advection associated with an mP air mass B) aA cPw air mass C) a large temperature gradient between the lake surface temperature the lower atmosphere D) strong southerly flow
C) a large temperature gradient between the lake surface temperature the lower atmosphere
Compared to continental air masses with the same air temperature, maritime air masses: A) have lower water vapor content. B) have about the same water vapor content. C) have higher water vapor content.
C) have higher water vapor content.
An mT air mass moving onto land in the Southeastern United States during the summer time typically becomes: A) conditionally unstable. B) more stable. C) more unstable. D) saturated.
C) more unstable.
Which of the following criteria is NOT a characteristic of a good source region? A) It must be very large. B) It must have uniform physical features. C) The air must able to stagnate over the area for long periods of time. D) The area must frequently experience cyclones.
D) The area must frequently experience cyclones.
The usual size of an air mass is: A) at most a few kilometers across. B) between 100 and 200 km across. C) around 1000 km across. D) at least 1600 km across.
D) at least 1600 km across.
Which of the following is NOT a good source region for air masses? A) the Gulf of Mexico B) central Canada C) the North Pacific D) the central United States
D) the central United States
Why are cT air masses of minor importance for the U.S.?
No large source region is near the U.S.
The ________ is characterized by a strong jet stream pulling mT air from Hawaii towards California.
Pineapple Express
Why are maritime air masses from the north Atlantic of only limited concern for weather in the U.S.?
Prevailing winds move them away from the U.S.
If the lowercase letter k appears at the end of an air mass identification code, what can be said about the changes likely to happen within that air mass?
The air mass is likely to become more unstable.
What does the lowercase letter w indicate about an air mass?
The air mass is warmer than the surface over which it is passing.
Lake-effect snowfall is caused by:
air mass modification related to the differential heating of land and water.
Siberian Express is the term used when:
an outbreak of bitterly cold air from Canada intrudes over a large part of the United States
Which two air masses are bitterly cold and very dry during winter?
cA and cP
"Lake-effect" snow is associated with the ________ air mass.
cP
The pronounced cooling that occurs on continents at high latitudes during winter leads to the formation of ________ air masses.
cP
In North America the ________ air mass forms only in the summer.
cT
Which air mass causes occasional drought to the southern Great Plains of the United States?
cT
An mP air mass is:
cold and humid
What weather is associated with cA air masses?
cold spells in winter
An air mass is often modified as it moves over the earth's surface. This modification is largely due to:
contact with the new surface below.
A region dominated by cyclones is more likely to produce an air mass than a region dominated by anticyclones. (t/f)
false
As wintertime cP or cA air moves outward from its source region, it carries its warm wet weather to the United States. (t/f)
false
Continental polar air masses do not form in the summer in North America. (t/f)
false
Lake-effect snow occurs only during the early spring. (t/f)
false
Maritime air masses form over landmasses. (t/f)
false
Maritime polar (mP) air masses have their greatest influence in the eastern United States. (t/f)
false
Maritime tropical (mT) air masses are the most important source of moisture along the Pacific Coast. (t/f)
false
Siberian Express weather events are generally confined to Alaska and western Canada. (t/f)
false
The Pineapple Express is responsible for supplying most of the moisture on the east side of the Rocky Mountains. (t/f)
false
The cP air-mass in North America originates in:
interior Alaska and Canada
Lines connecting places having equal rainfall on a map are called:
isohyets
Where would you expect to find the greatest amount of lake-effect snowfall?
on the leeward shore of the Great Lakes
An ideal source region of air masses should be:
physically uniform
An air mass is a body of air with:
similar values of temperature and moisture at any given altitude.
Air mass source regions tend to be dominated by:
slow moving anticyclones
The area where an air mass originates is called a:
source region
Why is Maritime Arctic left out of the air-mass classifications?
they rarely occur
When an air mass is warmer than the surface over which it is moving, its lower layers are chilled. (t/f)
true
A cT air mass is:
warm and dry
La Niña
- The reverse of El Niño
Tropical cyclones can be short or long-lived storms. Using Figure 1 of Hurricane Ike, how long was the storm rated a hurricane?
10 days
Which statement best describes why there are so many more tornadoes since the 1990s?
A and B only: Population increases result in more tornadoes reported than before Technology allows for easier spotting with radar and easier confirmation with smartphones
What do the letters k and w signify when added to an air mass identifier?
A k indicates that the air mass is colder than the surface underneath and a w indicates that the air mass is warmer than the surface.
Chinook winds
A warm and dry wind that blows down the east slope of the Rocky Mountains.
Which of these is NOT a process by which air masses are modified? A) calm winds B) lifting over mountains C) evaporation of water D) cooling from below E) heating from below
A) calm winds
An air-mass source region: A) is characterized by a general stagnation of atmospheric circulation. B) is best typified by the central United States. C) is generally an area characterized by a cyclonic circulation pattern. D) may consist of both land and water.
A) is characterized by a general stagnation of atmospheric circulation.
Which region of origin for mT air masses has the most impact on North American weather? A) mT air masses from the Gulf of Mexico B) mT air masses from the Northern Pacific C) mT air masses from the subtropical Pacific. D) mT air masses from Australia
A) mT air masses from the Gulf of Mexico
Air masses with cA and cP designations are typically: A) stable. B) conditionally unstable. C) absolutely unstable.
A) stable.
Why is warm, moist air considered the "fuel" for a hurricane?
Air cools as it rises. As air cools, water vapor will condense out as liquid water. Condensation releases heat, providing energy to the hurricane.
Westerlies
Air moving from the subtropical highs towards the subpolar lows is deflected by Coriolis, causing the westerlies in both hemispheres.
Which of the following statements about midlatitudes cyclones are correct?
All of the above: The cold front advances faster than the center of the storm, and the warm front advances more slowly than the center; Surface winds move counterclockwise. The entire cyclone moves from west to east.
Why are nocturnal (nighttime) tornadoes so dangerous?
All of the above: Many in danger are sleeping and unaware Warning systems are inadequate Twice as deadly as daytime due to response
All of the following accompany a classic New England nor'easter EXCEPT: A) heavy snowfall. B) a strong storm forming in Canada and moving into New England from the North. C) widespread power outages and transportation interruptions. D) mP air pulled in from the Atlantic Ocean.
B) a strong storm forming in Canada and moving into New England from the North.
When an area is experiencing several consecutive days of rather constant weather, it is experiencing: A) warm-front weather. B) air-mass weather. C) occluded front weather. D) cold-front weather.
B) air-mass weather.
Which air mass code letter is paired with the wrong word? A) c = continental B) t = temperate C) m = maritime D) a = arctic
B) t = temperate
List the basic criteria for an air-mass source region. Then, identify the source regions that influence North America, along with the types of air masses that originate in each.
Basic criteria: 1) extensive land area with a uniform surface and 2) air masses must be able to stagnate and remain in place long enough to reach equilibrium with the underlying surface.
When an air mass is warmer than the surface over which it is moving: A) the letter k is added after the air mass symbol. B) visibility within the air mass is usually very good. C) the air becomes more stable. D) the lapse rate in the air mass is increased.
C) the air becomes more stable.
Name two source regions for Maritime Tropical air masses.
Caribbean Sea. Subtropical Pacific. Gulf of Mexico
Southern Oscillation
Changes in the pressure pattern and trade wind strength (direction) in the tropical Pacific , a reversal of airflow between normally low atmospheric pressure over the western Pacific; the cause of El Nino
Midlatitude cyclones in the United States rotate in which direction?
Counterclockwise
The typical amount of time it takes for an air mass to pass over a given area is on the order of a few: A) minutes. B) weeks. C) hours. D) months. E) days.
E) days
Long-lasting rainstorms occur when a cold air front encounters a receding warm air front.
False
The only source of flooding related to a hurricane is from excessive rainfall.
False
When a cold air front moves rapidly toward a warm air front, there isn't time to predict the light and longer-lasting rains that result from the warm air dissipating.
False
Name two processes by which an air mass can be modified and give examples.
Heating from below (cP air moves over the Great Lakes and creates lake effect snow; mT air moves over the land in the SE U.S. and becomes more unstable), cooling from below (mT moves over a snow pack or cold ocean current), evaporation of water from below (cP air moves over the Great Lakes and creates LE snow), lifting over mountains (orographic lift of Pacific mP air).
What winds dominate the upper troposphere?
Jet Streams
July ITCZ
Just above the equator
January ITCZ
Just below the equator
What is the air mass type and source region for "nor'easters"?
Maritime Polar (mP) air-masses that form in the North Atlantic.
Name the three air mass types most important for the continental U.S.
Maritime polar (mP), continental polar (cP) and maritime tropical (mT).
valley breeze
Mountains facing the sun heat more intensely than shaded valley areas. This develops a thermal low during the day which produces a valley breeze.
Name two source regions of mP air masses.
North Atlantic; North Pacific
What is occlusion in a midlatitude cyclone?
Occlusion is the process by which a cold front overtakes a warm front.
Upwelling
Occurs where cool, deep waters, which are generally nutrient-rich, rise to replace vacating water
What are the two jet streams that impact the weather in the northern hemisphere?
Polar Jet Stream, Subtropical Jet Stream
How are rain patterns different near warm and cold fronts?
Rain near a cold front occurs over a smaller spatial area and is more intense than near a warm front
Where does rain occur in a warm front?
Rain occurs along and in front of a warm front.
Why does rain occur near a cold front?
Rising warm air cools, resulting in cloud formation and rain.
Based on long-term hurricane data and figure 2, what is the date with the most storms?
September 10
During what season is the Bermuda high strongest?
Summer
Hurricane Ike made multiple landfalls. Which US state was the first impacted directly?
Texas
subtropical highs
The Hadley cell sinks towards the surface about 20-30 degrees latitude to form the subtropical highs (large band of high pressure).
Define the northeast/southeast trade winds
The NE trade winds in the N Hemisphere and the SE trade winds in the S Hemisphere are deflected to the right and left.
mountain breeze
The cooler air subsides downslope into the valleys producing a mountain breeze.
Monsoons
There are 5 different typesd of monsoons
What was the first stage of Hurricane Ike (and most tropical cyclones)?
Tropical depression
During this stage, there is little to no rotation associated with the storm.
Tropical disturbance
Storms are given a name once they exceed 38 mph sustained winds during this stage.
Tropical storm
All of the following names refer to tropical cyclones: cyclone, typhoon, hurricane, willy willy.
True
In addition to the dangers of flooding and wind speed from the hurricanes, tornadoes are also commonly associated with hurricanes.
True
Rainstorms are generally shorter when a cold air front comes in quickly and collides with a warm air front.
True
When warm air collides with a cold air front, its slow journey up the slope of the cold air front causes longer rains.
True
El Niño
Warming of sea surface temperatures (SSTs) in the central and eastern tropical Pacific
What happens when air masses of different temperatures meet?
Well-defined boundaries form between the air masses
When do midlatitude cyclones stop producing storms?
When the cold front has completely taken over the warm front
What is a jet stream?
Wind currents 10 KM above the Earth that blow east to west at 200-400 KM per hour
During what season is the Icelandic low strongest?
Winter
Sea breeze
a cooling breeze from the sea (during the daytime)
Doldrums
a frequently windless area near the Equator
What is a tropical cyclone?
a low-pressure disturbance that develops over warm, tropical waters
Monsoon
a seasonal wind pattern in southern Asia that blows warm, moist air from the southwest during the (summer), bringing heavy rains, and cold, dry air from the northeast during the winter
Orographic lifting is
air forced to rise over a barrier, such as a mountain range.
Most warm air masses affecting North America
are moist
Which is the coldest air mass?
cA
A very cold and very dry airmass located over land.
cA - Continental Arctic
What air-mass type tends to dominate the weather in the U.S. east of the Rocky Mountains during winter? During summer?
cP during winter, mT during summer
During the summer months, which is the warmest air mass?
cT
A warm and dry airmass located over land.
cT - Continental Tropical
Polar cell
circulates air at the poles. 60N
Hadley cell
circulates air between the tropics and subtropics.Intense heating at the equator creates a zone of low pressure called the equatorial low, or the Intertropical Convergence Zone (ITCZ). The ITCZ (doldrums) is the rainiest latitude zone in the world. 30 N, 0 equator
Ferrel cell
circulates air in the middle latitudes 30N to 60N
Summer afternoon thundershowers in the southeastern United States are more than likely a result of
convection lifting
The scale that correlates wind speed and structural damage in a tornado is the
enhanced Fujita scale.
Which part of a hurricane consists of dry, descending air?
eye
In winter, cT brings fog, drizzle, and occasional moderate precipitation to NW Mexico and the SW United States. (t/f)
false
The physical properties of an air mass are independent of its place of origin. (t/f)
false
The properties of air masses change little, even if they travel thousands of kilometers. (t/f)
false
To qualify as an air mass, a large body of air must have the identically same temperature at the same altitude throughout the air mass, even if the body of air is 1,000 kilometers wide. (t/f)
false
Visibility is generally better in a w air-mass than in a k air-mass. (t/f)
false
cP and cA air masses are never experienced in the southern U.S. (t/f)
false
cT air masses are stable. (t/f)
false
The symbol used when classifying Maritime Polar air masses is MP. (t/f)
false (mP, not MP)
Santa Ana winds
hot desert winds from the east or northeast in southern california
Wave cyclones are most common
in the mid-latitudes
An air mass moves out of its source region. Two days later, the lower layers of the air mass are found to be warmer than they were originally. What letter should be added to the end of the air mass's classification code?
k
Where are tropical cyclones found?
lower and middle latitudes
A cold air mass originating over an ocean is designated
mP
The ________ air mass may produce an occasional "nor'easter" in the winter.
mP
The ________ air mass often originates as a different air mass in Siberia and is subsequently altered.
mP
Which air mass is unstable in the winter but stable in the summer?
mP
A cool and moist airmass associated with a coast.
mP - Maritime Polar
The ________ air mass provides much of the moisture for precipitation in the central and eastern United States.
mT
What air-mass contributes to the formation of thunderstorms in the central U.S.?
mT
An air mass from the Gulf of Mexico is called:
mT (maritime tropical)
A warm and moist airmass associated with a coast
mT - Maritime Tropical
Most of the precipitation for the region east of the Rocky Mountains comes from:
mT air masses
A warm, moist air mass from the Gulf of Mexico that moves over the land in the southeastern U.S. during the summer is likely to be classified as:
mTk
Air masses passing from the Gulf of Mexico over land in the Southeastern United States in the summertime are modified by the hot surface and become:
mTk
An air mass from the Gulf of Mexico that moves northward over the U.S. in winter would be labeled:
mTw
Topography and the upward and downward movements of cyclones and anticylones create ________ modifications of air masses.
mechanical (dynamic)
Air mass modifications produced by cyclones or topography rather than surface temperatures are called:
mechanical modifications
The two most important properties that should be relatively homogeneous at the same altitude in an air mass are:
moisture content and temperature.
The stability of an air mass can be affected by:
mountain ranges, cyclones, and anticyclones
zonal winds
move in an east/west or west/east direction
The highest frequency of tornadoes in the United States occurs in
oklahoma
A rainshadow is most often associated with which atmospheric lifting mechanism
orographic
What is the difference between the single cell and the three cell model?
single-cell model describes the general movement of the atmosphere,Three cell model-model divides each hemisphere into three cells. Hadley cell: circulates air between the tropics and subtropics. Ferrel cell: circulates air in the middle latitudes. Polar cell: circulates air at the poles.
The place where an air mass originates is known as the ________.
source region
Air masses are identified by a pair of letters, one lowercase and one uppercase. The uppercase letter (P, A, or T) refers to:
the approximate latitude of the air mass source region.
Land breeze
the flow of air from land to a body of water
In the United States, mid-latitude cyclone development is usually the result of
the interaction of cP and mT air masses.
In the United States, lake-effect snows occur over which area?
the leeward shores of the Great Lakes
Most mP air masses that influence the U.S. originate over:
the north Pacific
Tropical cyclones do not form exactly on the Equator because
there is no Coriolis force at the Equator.
Air masses are identified by two-letter codes. (t/f)
true
An air mass is an immense body of air characterized by homogeneous temperature and moisture content. (t/f)
true
An air mass with the designation k is likely to become more unstable. (t/f)
true
Continental tropical (cT) air masses are associated with summer drought conditions in the southern Great Plains. (t/f)
true
In the middle latitudes, atmospheric disturbances occur at the boundary zones separating air masses. (t/f)
true
Lake-effect snowfall is created as a direct result of air mass modification. (t/f)
true
Maritime Arctic air masses do not form very often. (t/f)
true
Maritime air masses have a higher water vapor content than continental air masses. (t/f)
true
Orographic precipitation in the western U.S. is often associated with the Pacific mP air mass (t/f)
true
The boundary of an air mass is a region of especially active weather. (t/f)
true
The lower-case letter m or c is used to designate the nature of the surface in the source region and hence the humidity characteristics of the air mass. (t/f)
true
The mT air masses from the Gulf-Caribbean-Atlantic source region greatly affect the weather of the United States east of the Rocky Mountains. (t/f)
true
The majority of the continental U.S. is not an air mass source region. (t/f)
true
The stormy winter weather associated with an invasion of mP air from the Atlantic into an area east of the Appalachians and north of Cape Hatteras is known as a nor'easter. (t/f)
true
When an air mass is warmer than the surface over which it moves, an inversion is likely. (t/f)
true
cT air masses are hot and dry. (t/f)
true
mP air masses over the northeastern United States produce stable, clear skies in the summer and heavy snowstorms in the winter. (t/f)
true
Characteristics of an air mass source region include:
uniformity of temperature and moisture.
Downwelling
water sinking or gravitating downwards.
Meridional winds
winds move in north/south or south/north direction.
