Water and Atmospheric Moisture

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Water and Atmospheric Moisture

• Advection Fog Near Canberra, Australia

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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

• Water on Earth
• 70 of surface area
• 97 salt-water by volume
• Fresh water
• 77 glaciers
• 22 ground water
• lt1 surface water
• Surface water
• 50 freshwater lakes
• 44 saltwater lakes
• 5 atmosphere
• lt1 rivers and streams

http//www.fourmilab.ch/earthview/vplanet.html
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Distribution of water
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Basics about Water

• Water molecule
• 2 atoms hydrogen 1 atom oxygen make a covalent
  bond (very strong) so water is very stable
• The molecule is however shaped like a bent
  paperclip
• Hydrogen bonding
• Because of the shape of the molecule there is a
  slight charge at either end of the molecule
• water is therefore a polar molecule

Polar molecules make good solvents
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Hydrogen bonding

• Hydrogen bonding
• Because of the shape of the molecule there is a
  slight charge at either end of the molecule
• water is therefore a polar molecule
• the positive H side attracts the negative O side
  of a neighboring water molecule and the molecules
  line up.
• This Hydrogen bonding is a very weak bond.

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Effects of Hydrogen bonding

• Causes water to bead.
• Allows you to slightly overfill a glass of water
  without it spilling over.

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Effects of Hydrogen bonding

• Allows heavier things like bugs to stand on top
  of the surface of water

Water Striderhttp//www.woodrow.org/teachers/bi/1
998/waterstrider/
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Effects of Hydrogen bonding

• Responsible for capillary action
• such as water moving higher in a straw than the
  level of water in the glass

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Phase changes in water

• A phase change is the transformation of a
  substance from one phase to another.
• Solid to liquid - melting
• liquid to solid - freezing / fusion
• Liquid to gas - Vaporization / evaporation
• gas to liquid - condensation
• Solid to gas - sublimation
• gas to solid - sublimation/deposition

condensation
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Latent Heat

• Latent heat is the heat required for a phase
  change
• Ice to water (latent heat of melting/fusion)
• Need to add 80 Calories for every gram
• Raising temperature of water from 0 deg to 100
  deg Celcius (sensible heat added)
• Need to add 100 Calories for every gram
• Water to water vapor (latent heat of
  vaporization/condensation
• Need to add 540 Calories for every gram

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Phase changes

• Sublimination
• Condensation Evaporation
• Freezing - Melting

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Heat
Water Vapor
Boiling
100
Water
Temperature (oC)
Melting
0
Ice
Latent
Sensible
Latent
Sensible
Sensible
80
100
540 Calories/gram
Heat absorbed as
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Water density

• Maximum density at 4 oC

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HumidityWater in the atmosphere

• 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
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Dew Point Temperature

• Temperature at which air becomes saturated with
  water vapor

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Dew Point Temperature

• Temperature at which air becomes saturated with
  water vapor

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Fog  

• Radiation fog
• Advection fog - when warm, moist air blows over
  cool land or water.
• Upslope fog
• Evaporation fog -
• Valley fog

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Radiation fog

• the most common type of fog. Produced over a land
  area when radiational cooling reduces the air
  temperature to or below its dewpoint.

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Advection Fog when warm, moist air blows over
cool land or water.
Figure 7.24
http//www.ace.mmu.ac.uk/Resources/Teaching_Packs/
Key_Stage_4/Weather_Climate/images/05c.jpg
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Advection Fog upslope Fog Whenever air rises,
it cools. If air is blown over high hills or
mountains, it may cool enough to reach its dew
point.
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Advection Fog upslope Fog Whenever air rises,
it cools. If air is blown over high hills or
mountains, it may cool enough to reach its dew
point.
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Advection Fog upslope Fog Whenever air rises,
it cools. If air is blown over high hills or
mountains, it may cool enough to reach its dew
point.
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Evaporation Fog when cool air flows over warm
water
Valley Fog
Figure 7.25
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Evaporation Fog when cool air flows over warm
water
Figure 7.25
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Evaporation Fog when cool air flows over warm
water
Figure 7.25
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Saturation Vapor Pressure

• Saturation vapor pressure is the pressure that
  water vapor creates when the air is fully
  saturated.

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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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Cloud Formation

• Moisture droplet
• Cloud-condensation nuclei

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