Fog/Foggy Weather
Overview
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Types of fog
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Advection fog
Radiation fog
Upslope fog
Evaporation (mixing) fog
Steam fog
• Fog formation
(1) by cooling…air is cooled below its saturation
(2) by evaporation and mixing
Condensation: review
• Important concept in fog and cloud
formation
• Evaporation vs. Condensation
Radiation fog
• Produced by the earth’s radiational cooling
• Forms best on clear nights + shallow moist
air near the ground + light winds
• Common over land in fall and winter
• Also called valley fog or Tule fog (e.g.,
central valley)
• Valley fog can persist for weeks unless
cold air moves in aloft or strong winds mix
it up.
http://www.cabrillo.edu/~crsmith/tule.html
Reference: wikipedia
Advection fog
• Forms by condensation of warm, moist air
carried by winds over the cold coastal
water
• common along summertime West Coast
– Water near the coast is much colder than
offshore water (see upwelling in Ch.8) +
onshore winds
• Fog disappear as it is pushed inland by
onshore winds (due to evaporation)
Burn off (of fog)
• Refers to dissipation of fog
• Sunlight warms the ground → enhances
evaporation of fog and mixing of air
Summary & additional info
• http://www.geog.ucsb.edu/~joel/g110_w08/
lecture_notes/california_fog/california_fog.
html