Sky and SpaceSky and Space

Lecture Outline #3Lecture Outline #3

Moisture in the AtmosphereMoisture in the Atmosphere

Moisture in the AtmosphereMoisture in the Atmosphere

HumidityHumidity CloudsClouds FogFog PrecipitationPrecipitation

Three Phases of WaterThree Phases of Water

HumidityHumidity

How much water vapor is in the How much water vapor is in the atmosphere?atmosphere?

3 Ways to Express Humidity3 Ways to Express Humidity

Absolute HumidityAbsolute Humidity Specific HumiditySpecific Humidity Relative HumidityRelative Humidity Dew PointDew Point

Relative HumidityRelative Humidity

WARM AIR CAN CONTAIN MORE WATER WARM AIR CAN CONTAIN MORE WATER VAPOR THAN COLD AIRVAPOR THAN COLD AIR

Changes in HumidityChanges in Humidity

Relative Humidity after CoolingRelative Humidity after Cooling

Relative Humidity and TemperatureRelative Humidity and Temperature

Warm Air is Capable of Holding More Water Vapor than Cold Warm Air is Capable of Holding More Water Vapor than Cold AirAir

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)

Dew PointDew Point

When air is cooled to a certain temperature, When air is cooled to a certain temperature, it can reach 100% Relative Humidity it can reach 100% Relative Humidity (saturation)(saturation)

Condensation Occurs at this Condensation Occurs at this temperaturetemperature

Dew PointDew Point

When air is cooled to a certain temperature, When air is cooled to a certain temperature, it can reach 100% Relative Humidity it can reach 100% Relative Humidity (saturation)(saturation)

Condensation Occurs at this temperatureCondensation Occurs at this temperature

This is the Dew Point This is the Dew Point TemperatureTemperature

Basics of Cloud FormationBasics of Cloud Formation

Warm air contains more water vapor than Warm air contains more water vapor than cold aircold air

Hot fluids rise (convection)Hot fluids rise (convection) In the troposphere, temperature decreases In the troposphere, temperature decreases

with altitudewith altitude When water vapor in the air cools, it When water vapor in the air cools, it

condensescondenses

Cloud FormationCloud Formation

Adiabatic CoolingAdiabatic Cooling

Rising Parcel cools quicker than Rising Parcel cools quicker than surrounding airsurrounding air

Parcel remains warmer than the Parcel remains warmer than the surrounding airsurrounding air

Conditional InstabilityConditional Instability Rising parcel cools Rising parcel cools

quicker than quicker than surrounding airsurrounding air

Reaches dew pointReaches dew point

Then cools slower Then cools slower than surrounding than surrounding airair

What forces air to rise?What forces air to rise?