Air Masses

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Air Masses

• An immense body of air, usually more than 1,000
• miles across and several Km thick
• Characterized by a similarity of temperature,
  moisture
• It carries those characteristics with them and
  can affect
• Large portions of a continent.
• Defined by their source regions

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Air Masses
Source Regions an area where an air mass
acquires its characteristics
Temperature
Polar (P) originate in high latitudes toward
poles Tropical (T) originate in low latitudes
Moisture
Continental (c) originate over land Maritime
(m) originate over water
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Air Masses
Four Basic Air Masses

1. Continental Polar (cP)
2. Continental Tropical (cT)
3. Maritime Polar (mP)
4. Maritime Tropical (mT)

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Air Masses
FIG 9-1
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Fronts
The transition zone between two air masses
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Fronts
Cold fronts
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Before Passing After Passing
Winds south-southwest west-northwest
Temperature warm steadily dropping
Pressure falling steadily rising steadily
Clouds increasing Ci, Cs and Cb Cu
Precipitation short period of showers showers then clearing
Visibility fair to poor in haze good, except in showers
Dew Point high remains steady lowering
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Cold Fronts Wind Shifts
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Cold Fronts Temperature and Dewpoints
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Cold Fronts Precipitation and clouds
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Fronts
Warm fronts
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Before Passing After Passing
Winds south-southeast south-southwest
Temperature cool-cold, slow warming warmer, then steady
Pressure usually falling slight rise, followed by fall
Clouds in this order Ci, Cs, As, Ns, St, and fog occasionally Cb in summer clearing with scattered Sc occasionally Cb in summer
Precipitation light-to-moderate rain, snow, sleet, or drizzle usually none, sometimes light rain or showers
Visibility poor fair in haze
Dew Point steady rise rise, then steady
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Warm Fronts Wind Shift
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Warm Fronts Temperatures and Dewpoints
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Warm Fronts Precipitation
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Fronts
Stationary fronts
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Fronts
Occluded fronts
The cold front overtakes The warm front
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Fronts
Dryline a dewpoint front
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Cyclones and Associated Fronts