Fog/Stratus/VisibilityAdvection Fog
![Photo of fog over Arctic Ocean with sea ice](media/graphics/arctic_ocean_fog_bank.jpg)
Advection fog, common in the Arctic, occurs when air is transported from over a warmer surface to over a cooler surface. The air mass might have a high relative humidity prior to advection, or the cooler surface can also be a moisture source. With enough humidity and enough cooling, the air saturates and fog forms.
![Photo of coastal fog in the Arctic city of Iqaluit in the Canadian Arctic](media/graphics/iqaluit_fog.jpg)
The irregular coastlines of the Arctic help set the preconditions to this fog formation. Boggy tundra and open ocean provide moisture. The cold ocean promotes formation of a low-level inversion. The coastline provides strong temperature gradients so that fog can form as air flows on and offshore.