Significant weather in the weather field is any weather phenomena, which reduces horizontal visibility to less than 7 miles and “vertical visibility” less than 1,000 ft.
The greatest frequency of fog in the vicinity of Denmark occurs from mid autumn to mid spring. During this period of colder surface temperatures, the great stabilizing affect of these colder temperatures and the moisture available from the nearby waters cause fog to be relatively frequent. There is also a relatively high frequency of occurrence of frontal fog in the vicinity of Denmark.
Sea Fog is formed when warmer air from the south drifts northward across an increasingly cooler sea surface. In the summer, sea fog occurs along the coast of Norway frequently enough to be a problem to maritime and air traffic. Maximum frequency of fog is in July.
Frontal Fog is formed when relatively warmer air is gently lifted along the gradual slope of a warm front. This type of fog usually does not usually create problems for the coastal regions of Scandinavia as it is usually found in the interior regions. The Vikings were sure to have encountered this type of fog, but usually on their inland travels. They would not often encounter this type of fog on their ocean/coastal travels.
Radiation Fog is formed when moist air at the surface weak winds are cooled. The cooling process can happen at night or when relatively warmer ocean air is brought over much cooler land. This type of fog usually occurs after the passage of a frontal system when moist oceanic air is brought to the Scandinavian Peninsula countries.
Stratus Clouds are a flat type of cloud formed under stable atmospheric conditions. They typically form above the ground but can be formed on the ground at which point they are termed “fog” and during the daily heating (the sun rises and warms the earth) the fog lifts and is termed a stratus cloud. Higher elevations which are still in the clouds are foggy. Often when the Vikings were traveling along the coastal shores their foggy conditions during the night and morning hours would clear out lift by late morning.
How the Vikings could use fog
- They could plan an invasion and use the fog as a cloak for a surprise attack and then retreating in the fog after. By having predestined meeting places they could meet there after before returning home.
- When traveling from the open ocean, they could wait until fog began to form prior to gaining entrance to their coastal regions leaving any followers unsure of where they entered.
- Since fog forms along moist areas, they could look for fog over the hills to quickly find where streams, rivers and lakes were located.
- When fog begins to form at night there is a good chance that the night may not be too windy, and that knowledge could be utilized in many ways.
Since their cooking fires were within their homes with open holes in the roofs, they could cook or cure meats under a heavy fog.