1. Fog/Foggy Weather

2. Overview Types of fog –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

3. Condensation: review Important concept in fog and cloud formation Evaporation vs. Condensation

4. 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.

6. Reference: wikipedia http://www.cabrillo.edu/~crsmith/tule.html

7. 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)

9. Burn off (of fog) Refers to dissipation of fog Sunlight warms the ground → enhances evaporation of fog and mixing of air

10. Summary & additional info http://www.geog.ucsb.edu/~joel/g110_w08 /lecture_notes/california_fog/california_fog.htmlhttp://www.geog.ucsb.edu/~joel/g110_w08 /lecture_notes/california_fog/california_fog.html