Altistumistilaa

Altistumistilaa is a Fennic term used to describe a specific type of fog or cloud layer that forms over the sea in the vicinity of the Gulf of Bothnia, in northern Europe, particularly in regions of Finland and Sweden.

The term 'altistumistilaa' is derived from the indigenous languages spoken by the Sami people, one of the indigenous groups of the region. It is not a recognized meteorological term in international usage, and its meaning is unique to the local Fennic dialects.

Observations of altistumistilaa suggest that it appears when cold air from the Arctic or from a channel of sea between two high-lying landmasses meets warm, moist air from the Gulf Stream or other ocean currents. This collision of different air masses results in the formation of a stratus cloud layer with fog patches that can be difficult to see due to turbulence and small-scale thermal currents.

The phenomenon is most commonly observed from the coastal areas, particularly in shipping routes and inter-island ferry passages. The viewing of altistumistilaa is not limited to daytime; observations indicate that it is also visible on nights with light wind conditions, especially under the clear sky portion.

Altistumistilaa typically appears in late spring, in close association with climate conditions in Scandinavia such as increased ship traffic and smoking plumes.