Chapter 8 Weather

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Chapter 8Weather
Geosystems 5e An Introduction to Physical
Geography

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Robert W. Christopherson Charlie Thomsen
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3 circulation cells per hemisphere
Tropics Hot Rising Air
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Polar Jet stream
Subtropical Jet stream
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Air Masses
Figure 8.2
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Air Masses
Figure 8.2
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Jet Stream
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Jet Stream
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Weather Map
Figure 8.18
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Cold Front
Figure 8.11
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Warm Front
Figure 8.13
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Average Annual precipitation
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Air Mass Modification Lake Effect
Figure 8.5
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Cyclogenesis mid-latitude cyclones

• Cyclones initiate at the polar front (an area of
  low pressure), where warm and cold air collide.

• Air spirals into the low pressure system
• Warm air moves in on the eastern side of the low
• Cold air moves south from the western side.

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(1) Cyclogenesis
Leaf Clouds
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(2) Open Stage
Comma Clouds
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(3) Occluded Stage
Cold Front overtakes warm front as they rotate to
create an Occluded front
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(4) Dissipating Stage
Cold Front entirely undercuts warm front cutting
off lifting mechanism
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(1) Initiation Leaf Clouds
(2) Open stage
http//henry.pha.jhu.edu/ssip/asat_int/cyclogen.ht
ml
(3) Occluded stage cold front overtakes warm
front
(4) Dissolving stage
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(1) Initiation Leaf Clouds
(2) Open stage
(4) Dissolving stage
(3) Occluded stage
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Midlatitude Cyclone
Figure 8.15
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Storm Tracks
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• Cyclone movie from Nov 11th, 2003
  mid_lat_cyclone.mov

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Atmospheric Lifting Mechanisms 
Convergence
Convection
Orographic lifting
Fronts
Figure 8.6
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Orographic Lifting
Figure 8.9
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Orographic Lifting
Figure 8.9
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Orographic Lifting
Figure 8.10
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Frontal Lifting

• Cold Fronts
• Cold air forces warm air aloft
• 400 km wide (250 mi)
• Warm Fronts
• Warm air moves up and over cold air
• 1000 km wide (600 mi)

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Cold Front
Figure 8.11
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Warm Front
Figure 8.13
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Weather Forecasting
Figure 8.17
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Weather Map
Figure 8.18
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Violent Weather

• Thunderstorms  
• Tornadoes  
• Tropical Cyclones  

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Thunderstorms

• Form from
• unstable atmosphere
• Lifting Mechanism
• moisture in the lower and/or mid atmosphere

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Thunderstorms
Figure 8.21
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If you warm the surface what happens to the
environmental lapse rate???
Figure 7.18
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Thunderstorms
Figure 8.21
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Thunderstorms
Figure 8.23
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Tornadoes
Figure 8.24
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Tornadoes
Figure 8.26
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• Tornados movie
• tornados.mov

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Tropical Cyclones
Figure 8.29
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Tropical Cyclones
Figure 8.29
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1995 Atlantic Storm Season
Figure 1
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1995 Atlantic Storm Season
Figure 2
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Hurricane Andrew
Figure 8.30
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Weather Forecasting
Figure 8.17
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Probabalistic Forecasts TornadosNov. 11th,
2003NWS http//www.spc.noaa.gov/products/outlook
/
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Probabalistic Forecasts Severe Winds Nov. 11th,
2003NWS http//www.spc.noaa.gov/products/outlook
/
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Probabalistic Forecasts Large HailNov. 11th,
2003NWS http//www.spc.noaa.gov/products/outlook
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End of Chapter 8
Geosystems 5e An Introduction to Physical
Geography

•  

Robert W. Christopherson Charlie Thomsen