| Sea of clouds | |
| Image Location: | Chamonix valley clouds.jpg |
| Image Name: | Sea of clouds in Chamonix-Mont-Blanc. |
| Level: | low |
| Appearance: | Uniform with ondulations |
| Precipitation: | no |
A sea of clouds is an overcast layer of stratocumulus clouds, as viewed from above, with a relatively uniform top which shows undulations of very different lengths resembling waves on the sea.[1] A sea of fog is formed from stratus clouds or fog and does not show undulations.[2]
In both cases, the phenomenon looks very similar to the open ocean. The comparison is even more complete if some mountain peaks rise above the clouds, thus resembling islands.
A sea of clouds forms generally in valleys or over seas in very stable air mass conditions such as in a temperature inversion. Humidity can then reach saturation and condensation leads to a very uniform stratocumulus cloud, stratus cloud or fog. Above this layer, the air must be dry. This is a common situation in a high-pressure area with cooling at the surface by radiative cooling at night in summer, or advection of cold air in winter or in a marine layer.