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 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 of the following is NOT an air mass that influences North America? A) mA B) cP C) mT D) cA E) mP

A) mA

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.

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.

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.

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.

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

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.

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.

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

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

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 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

The symbol used when classifying Maritime Polar air masses is MP. (t/f)

false (mP, not MP)

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

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

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

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)

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

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

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.

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

Why is Maritime Arctic left out of the air-mass classifications?

they rarely occur

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

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 is moving, its lower layers are chilled. (t/f)

true

When an air mass is warmer than the surface over which it moves, an inversion is likely. (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.

A cT air mass is:

warm and dry