coastal covering
A type of fog formed by the movement of air is sea fog. This is common in spring and early summer along the east coast of both Scotland and England, although it is also seen elsewhere. A sunny sky can suddenly dull and the golden sands become enveloped in a thick, chilling fog. A typical scenario would be a gentle breeze leaving Denmark with a temperature of 20°C to 22°C. The chill North Sea it crossed would have a temperature no higher than 10°C. By the time it reached the east coast, it would be chilled to its dew point, resulting in a dank, raw fog, sometimes drizzle laden. This form of fog envelopes beaches, headlands and piers in a ghostly grey world. It can extend some distance out to sea and creep into estuaries and across adjacent low-lying areas. Along the North Sea coast this is called haar or sea fret. If the wind is too strong, the air does not have time to cool, or is lifted into a higher cloud sheet. If the wind is very light, the fog may be restricted to the headlands or stay further out to sea. As the air moves in from the coast, it dries out. As a result, a short trip inland can result in leaving the gloom and entering into clear conditions. The south-west and west coast of Britain can experience sea frets under different conditions. They occur when a moist air mass, brought by south-westerly winds emanating from an Atlantic warmed by the Gulf Stream, cools slowly on its journey towards Britain. Once the dew point is reached, the fret veils the cliffs and cloaks the headlands.