Dew & Fog
Water CycleEvaporation, transpiration +
condensation
Evaporation rate greatest at equator
Dew Point vs. DewAir can hold water vapour =
humidity
Dew Point vs. DewAbsolute Humidity – amount of
water vapour in the air
Relative Humidity - % of water in the air
Dew Point vs. DewWhen the air cannot hold anymore
vapour it is 100% saturated
This is the Dew Point
Dew Point vs. DewAt the Dew Point – water vapour
condenses
Warmer the air temperature, higher the dew point
Dew Point vs. DewCondensed water vapour = dew
When it freezes = frost
FogWhen air close to the ground cools
enough & reaches the dew point
Water vapour can form a low cloud
Radiation Fog & Advection Fog
Radiation FogForms during cloudless & windless
nights
low lying fog
Radiation FogAt night, ground cools rapidly
Cools the air
Air reaches dew point, condenses into fog
Advection FogNeeds air to be moving (wind)
Warm, moist air moves over a cool surface (snow or water)
Advection FogCan cause problems in Vancouver,
Victoria, Seattle, San Francisco