Chapter 7 Water and Atmospheric Moisture

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Chapter 7Water and Atmospheric Moisture
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Water and Atmospheric Moisture

• Water on Earth  
• Unique Properties of Water  
• Humidity  
• Atmospheric Stability  
• Clouds and Fog  

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Land and Water Hemispheres
Figure 7.2
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Ocean and Freshwater Distribution
Figure 7.3
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Unique Properties of Water  

• Heat Properties 
• Phase change
• Sublimation
• Latent heat 
• Vaporization
• Condensation
• Heat Properties of Water in Nature  
• Latent heat of sublimation

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Basics about Water 2 atoms hydrogen 1 atom
oxygen make a covalent bond (very strong)
so water is very stable Molecule is shaped like
a bent paperclip

• with the O side having a negative charge and the
  H side having a positive charge

• the positive H side attracts the negative O side
  of a neighboring water molecule
• called hydrogen bonding (weak)

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• Hydrogen bonding
• Responsible for the surface tension of water
• allows heavier things like bugs to stand on top
  of the surface of water
• allows you to slightly overfill a glass of water
  without it spilling over.
• Responsible for capillary action
• what happens when you set the edge of a
  papertowel down on a puddle of water?
• The water is pulled into the dry part of the
  towel because each molecule is drawing the next
  molecule in
• Same thing happens in soils, which will become
  important when we talk about the hydrologic cycle

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Phase changes

• Sublimination
• Condensation Evaporation
• Freezing - Melting

Figure 7.4
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Heat Transfer
Figure 4.10
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Latent and sensible heat
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Latent heat
Boiling
Water Vapor
100
Water
Temperature (oC)
0
Ice
Melting
Heat added
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Water density
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Humidity

• Relative Humidity  
• Saturation
• Dew point
• Expressions of Relative Humidity  
• Vapor pressure
• Specific humidity
• Instruments

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Relative Humidity
Actual water vapor content of air

x 100
Maximum water vapor capacity of air
Dew Point Temperature
Figure 7.7
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Saturation Vapor Pressure
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Water Vapor in the Atmosphere
Figure 7.9
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Global Latent Heat
Figure 4.19
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Daily Humidity Patterns
Figure 7.10
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Seasonal Humidity Patterns
Winter
Summer
Figure 7.10
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Humidity Instruments hair hygrometer
Figure 7.13
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Humidity Instruments Sling Hygrometer
Rate of evaporation is faster (more heat loss)
when humidity is low
Figure 7.13
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Atmospheric Stability
Will the Balloon float up or stay where it is (or
sink downward)? If the air in the balloon is
less dense than the air outside ? it floats
up If the air in the balloon is more dense than
the air outside ? it sinks
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Atmospheric Stability  

• Adiabatic Processes  
• Environmental Lapse rate
• Actual Lapse rate
• Rate at which temperature decreases with
  altitude.
• Dry adiabatic lapse rate
• Lapse rate of dry air
• Moist adiabatic lapse rate
• Lapse rate of water vapor saturated air

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Adiabatic Processes
Figure 7.16
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Adiabatic Processes

• Dry adiabatic rate (dry air)
• 10 C/ 1000 m
• 5.5 F/ 1000 ft
• Moist adiabatic rate (saturated air)
• 6 C/ 1000 m
• 3.3 F/ 1000 ft

Figure 7.17
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 Stable conditions
3000
MAR 6oC/km
DAR 10oC/km
2000
Altitude (m)
Environmental Lapse rate 5oC/km
1000
Temperature (oC)

• Instructions
• Take a balloon and fill it with air at ground
  level (note the humidity).
• Move it up in the atmosphere
• As the Pressure decreases the air in the balloon
  expands and becomes cooler
• Is the air in the balloon at a lower temperature
  than the surrounding air?

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 Stable conditions
Environmental Lapse rate 5oC/km
3000
MAR 6oC/km
DAR 10oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is DRY at ground level the temperature
  IN THE BALLOON at 2000 m is ? 5 oC
• The temperature of the air outside the balloon is
  ? 16 oC
• The air in the balloon is denser so the balloon
  WILL SINK!!!

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 Stable conditions
Environmental Lapse rate 5oC/km
3000
MAR 6oC/km
DAR 10oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is MOIST (saturated) at ground level
  the temperature IN THE BALLOON at 2000 m is ?
  13 oC
• The temperature of the air outside the balloon is
  ? 16 oC
• The air in the balloon is denser so the balloon
  WILL SINK!!!

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 Unstable conditions
3000
DAR 10oC/km
MAR 6oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is MOIST (saturated) at ground level
  the temperature IN THE BALLOON at 2000 m is ?
  13 oC
• The temperature of the air outside the balloon is
  ? 2 oC
• The air in the balloon is denser so the balloon
  WILL FLOAT!!!

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 Unstable conditions
3000
DAR 10oC/km
MAR 6oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is DRY at ground level the temperature
  IN THE BALLOON at 2000 m is ? ? oC
• The temperature of the air outside the balloon is
  ? ? oC
• The air in the balloon is _______ so the balloon
  WILL _______!!!

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 Conditionally Unstable
Environmental Lapse rate 7oC/km
3000
MAR 6oC/km
DAR 10oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is MOIST at ground level the
  temperature IN THE BALLOON at 2000 m is ?
  ? oC
• The temperature of the air outside the balloon is
  ? ? oC
• The air in the balloon is _______ so the balloon
  WILL _______!!!

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 Conditionally Unstable
Environmental Lapse rate 7oC/km
3000
MAR 6oC/km
DAR 10oC/km
2000
Altitude (m)
1000
Temperature (oC)

• Is the air in the balloon at a lower temperature
  than the surrounding air?
• If the air is DRY at ground level the temperature
  IN THE BALLOON at 2000 m is ? ? oC
• The temperature of the air outside the balloon is
  ? ? oC
• The air in the balloon is _______ so the balloon
  WILL _______!!!

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Stable and Unstable Atmospheric Conditions
Figure 7.18
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If you warm the surface what happens to the
environmental lapse rate???
Figure 7.18
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Clouds and Fog

• Cloud Formation Processes  
• Cloud Types and Identification  
• Fog  

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Cloud Formation

• Moisture droplet
• Cloud-condensation nuclei

Figure 7.20
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Cloud Types and Identification  
Figure 7.22
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Cumulonimbus Development
Figure 7.23
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Fog  

• Advection fog
• Evaporation fog
• Upslope fog
• Valley fog
• Radiation fog

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Advection Fog air migrates up or down and
becomes saturated with water vapor
Figure 7.24
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Advection Fog Valley Fog
Figure 7.25
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Advection Fog upslope Fog
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Radiation Fog
Figure 7.26
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Fog Harvesting
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End of Chapter 7

• Geosystems 5e
• An Introduction to Physical Geography

Robert W. Christopherson Charlie Thomsen
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