1. Sky and SpaceSky and Space
Lecture Outline #3Lecture Outline #3
Moisture in the AtmosphereMoisture in the Atmosphere

2. Water in the AtmosphereWater in the Atmosphere
 HumidityHumidity
 CloudsClouds
 FogFog
 PrecipitationPrecipitation

3. Three Phases of WaterThree Phases of Water

5. HumidityHumidity
 How much water vapor is in theHow much water vapor is in the
atmosphere?atmosphere?

6. 3 Ways to Express Humidity3 Ways to Express Humidity
 Absolute HumidityAbsolute Humidity
 Specific HumiditySpecific Humidity
 Relative HumidityRelative Humidity

7. Relative HumidityRelative Humidity
 WARM AIR HOLDS MORE WATERWARM AIR HOLDS MORE WATER
VAPOR THAN COLD AIRVAPOR THAN COLD AIR

8. Changes in HumidityChanges in Humidity

9. Relative Humidity after CoolingRelative Humidity after Cooling

10. Relative Humidity and TemperatureRelative Humidity and Temperature
 Warm Air is Capable of Holding More Water Vapor than ColdWarm Air is Capable of Holding More Water Vapor than Cold
AirAir

11. Dew PointDew Point
 When air is cooled, it can reach 100%When air is cooled, it can reach 100%
Relative Humidity (saturation)Relative Humidity (saturation)

12. Dew PointDew Point
 When air is cooled to a certain temperature,When air is cooled to a certain temperature,
it can reach 100% Relative Humidityit can reach 100% Relative Humidity
(saturation)(saturation)
 There is more CondensationThere is more Condensation
than evaporation after dew pointthan evaporation after dew point
is reached.is reached.

13. Dew PointDew Point
 When air is cooled to a certain temperature,When air is cooled to a certain temperature,
it can reach 100% Relative Humidityit can reach 100% Relative Humidity
(saturation)(saturation)
 Condensation Occurs at this temperatureCondensation Occurs at this temperature
 This is the Dew PointThis is the Dew Point
TemperatureTemperature

14. Basics of Cloud FormationBasics of Cloud Formation
 Warm air contains more water vapor thanWarm air contains more water vapor than
cold aircold air
 Hot fluids rise (convection)Hot fluids rise (convection)
 In the troposphere, temperature decreasesIn the troposphere, temperature decreases
with altitudewith altitude
 When water vapor in the air cools, itWhen water vapor in the air cools, it
condensescondenses
 An air parcel can cool at a different rateAn air parcel can cool at a different rate
than surrounding airthan surrounding air

15. Cloud FormationCloud Formation

16. Adiabatic CoolingAdiabatic Cooling

17. Rising Parcel cools quicker thanRising Parcel cools quicker than
surrounding airsurrounding air

18. Parcel remains warmer than theParcel remains warmer than the
surrounding airsurrounding air

19. Conditional InstabilityConditional Instability
 Rising parcel coolsRising parcel cools
quicker thanquicker than
surrounding airsurrounding air
 Reaches dew pointReaches dew point
 Then cools slowerThen cools slower
than surroundingthan surrounding
airair

20. What forces air to rise?What forces air to rise?