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What Causes Fog? |
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| Fog is a cloud that touches the ground. It is simply a cloud of little water droplets that is located at ground level. Fog forms when the air at ground level is cooled enough to reach its saturation point. This is also known as Relative Humidity that equals 100%. Source: http://www.physicalgeography.net/fundamentals/8f.html |
| Relative Humidity: |
The amount of water vapor in the air at any given time is usually less than that required to saturate the air. The relative humidity is the percent of saturation humidity. The saturation humidity is when no further water can be held in a gaseous state. 1) First, the warmer air is, the more water vapor it can "hold." 2) Dew point is a measure of how much water vapor is actually in the air. 3) Relative humidity is a measure of the amount of water in the air compared with the amount of water the air can hold at the temperature it happens to be when you measure it. |
- Types of Fog - |
| Radiation or Ground Fog |
| Radiation fog is relatively shallow fog. Radiation fog is also known as ground fog. It is produced near the ground. It is formed by the cooling of land after sunset by thermal (infrared) radiation in calm conditions with a clear sky. The cool ground produces condensation in the nearby air by heat conduction. |
  Source: http://www.islandnet.com/~see/weather/almanac/arc2002/alm02sep.htm |
| Upslope fog |
| Upslope fog forms when winds blow air up a slope. This flow upwards causes the warm air to cool as it rises, which causes the moisture in it to condense and form fog. |
 Source: http://www.islandnet.com/~see/weather/almanac/arc2002/alm02sep.htm |
| Valley fog |
| Valley fog forms in mountain valleys, often during the fall, winter and early spring. It is the result of a temperature inversion caused by heavier cold air settling into in a valley, with warmer air passing over the mountains above. It is essentially radiation fog confined by local topography, and can last for several days in calm conditions. |
 Source: http://www.islandnet.com/~see/weather/almanac/arc2002/alm02sep.htm |
| Advection fog |
| Advection fog is created when moist air passes over a cool surface, and the air is cooled. As the air is cooled it reaches its relative humidity saturation point and fog is formed. This kind of fog is common as a warm front passes over an area with significant snow pack. Source: http://en.wikipedia.org/wiki/Fog |
 Source: http://www.islandnet.com/~see/weather/almanac/arc2002/alm02sep.htm |
| Evaporation Fog |
Evaporation Fog is a specific type of advection fog. It occurs when you get cold air advancing over warm water or warm, moist land surfaces. In this situation, fog forms as water from the surface evaporates into the cold air and then saturates Source: http://www.physicalgeography.net/fundamentals/8f.html |
 Source:http://www.oceansatlas.com/unatlas/issues/emergencies/OceanPhenHDNO/Dangerous.html |
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