What are Air Masses and Fronts? (Chapter 16 Section 2)

1
What are Air Masses and Fronts? (Chapter 16
Section 2)

• Terms air mass, front, cyclone, anticyclone,

2
What are air masses and fronts?P. 490

• What are the major air masses that influence the
  weather in the U.S.?
• What is one source region of a maritime polar air
  mass?
• What are the characteristics of an air mass whose
  two-letter symbol is cP?
• What are the four major types of fronts?

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Air Masses

• Air masses are large bodies of air where
  temperature and moisture content are constant
  throughout.
• Moisture content and temperature of a mass are
  determined by the area over which the air mass
  forms.
• These areas are called source regions.

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Types of Air Masses

• maritime (m) forms over water wet
• Continental (c) forms over land dry
• Polar (P) forms over the polar regions cold
• Tropical (T) develops over the tropics warm

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Cold Air Masses

• Three polar air masses
• Continental polar (cP) forms over northern
  Canada brings extremely cold weather during
  winter brings cool dry weather during summer
• Maritime polar (mP) forms over North Pacific
  Ocean cool, very wet rain and snow during
  winter foggy during summer
• Maritime polar (mP) forms over North Atlantic
  Ocean cool, cloudy and precipitation during
  winter mild, cloudy during summer.

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Warm Air Masses

• There are three warm air masses that affect the
  U.S.
• Maritime tropical (mT) forms over warm water in
  the Pacific ocean
• (mT) forms over the Gulf of Mexico and the
  Atlantic Ocean brings hot, humid weather and
  hurricanes and thunderstorms during the summer
  In winter, brings mild, cloudy weather
• Continental Tropical (cT) forms deserts of Mexico
  and Southwestern U.S. brings clear, hot, dry
  weather during summer

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Fronts

• The boundary between air masses of different
  densities and different temperatures
• Cold Front cold air moves under warm air
  brings thunderstorms
• Warm Front warm air moves over cold air brings
  drizzly rain followed by clear and warm weather.

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Fronts

• Occluded Front warm air mass is caught between
  two colder air masses. Brings cool temperature
  and large amounts of rain.
• Stationary Front cold air mass meets warm air
  mass remain separate not enough energy to move
  warm air above cold air mass can bring many days
  of cloudy, wet weather.

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Air Pressure and Weather

• Cyclones areas in the atmosphere that has
  lower pressure than the surrounding areas and has
  winds that spiral toward the center. Brings
  clouds and rain.
• Anticyclones the rotation of air around a high
  pressure center in the direction opposite to
  Earths rotation. Brings dry, clear weather.

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Quick Check

• What kind of front forms when a cold air mass
  displaces a warm air mass?
• A. a cold front
• B. a warm front
• C. an occluded front
• D. a stationary front

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Quick Check

• A maritime tropical air mass contains
• A. cold, dry air.
• B. warm, dry air.
• C. warm, wet air.
• D. cold, wet air.

12
Quick Check

• A front that forms when a warm air mass is
  trapped between two cold air masses and is forced
  to rise is a(n)
• A. stationary front.
• B. occluded front.
• C. warm front.
• D. cold front.