Fog is a collection of liquid water droplets or ice crystals suspended in the air at or near the Earth’s surface. The moisture in the fog is often generated locally such as from a nearby body of water.
Fog is distinguished from mist only by its density resulting in decrease in visibility. Fog reduces visibility to less than 1 km, whereas mist reduces visibility to no less than 1 km.
Fog begins to form when water vapour condenses into tiny liquid droplets in the air. This can be achieved by either adding moisture to the air or dropping the ambient air temperature. Fog can form at lower humidity, and fog can sometimes not form with relative humidity at 100 per cent. Fog is dense enough to be illuminated by light that passes through gaps in a structure or tree, which leads to invisibility; but, thin enough to let a large quantity of that light pass through to illuminate points further on.
WORlD’S FOGGIEST PlACES
The foggiest place in the world is the Grand Banks off the island of Newfoundland, the meeting place of the cold labrador Current and the much warmer Gulf Stream from the South. Some of the foggiest areas in the world include Argentina and Point Reyes in California.