Geog Chapter 7 Lecture/Lab
October 30, 2013 6:03 PM
- Fog is clouds in direct contact with the ground
- Less than 1 km is visible at a distance
- Calm, not a lot of wind
- Very stagnant air movement
1. By cooling:
a) Advection fog
Example: Cold ocean current brings cold air across coast of Vancouver to a pool of warm air
coming towards North America. By ADVECTION, warm air is moving. Howeverit is in direct contact
with cold water and temperaturebegins to drop by process of cooling. Reaches dew point
temperature,becomessaturated, becomesfog and develops right along our coastline.
b) Radiation fog
Example: At night, no clouds, the best setting. Under cloudless condition, Earth is losing heat to
outer space fast, and infrared radiation by Earth goes up. Overnight, heat alters fast and ground
becomesreally cold really fast and air directly above cools at fast rate too. Processof cooling
because of heat loss.
2. Adding water vapour
Example: Landmass on left side, body of water on right side. On land mass, pool of cold air. Cold
air moving from left to right (towards body of water, in direct contact). Cold air is now sitting on
body of water and water evaporatesupwards into cold air, adding water vapour to the air. Even
very cold air could make it saturated, so fog appears directly on surface of water. Known as
EVAPORATION FOG (adding water vapour to the air).
- Only these 3 types needed to know.
1. Temperaturecharacteristics of an air mass.
- Arctic (A): pretty cold
- Polar (P): also very cold
- Tropical (T): very warm