stratus

Stratus is a type of cloud characterized by a horizontal, uniform gray layer that covers much or all of the sky. The term comes from the Latin stratus, meaning spread out or laid flat.

Stratus forms in stable, moist air near the ground and is classified as a low-level cloud, typically forming below about 2,000 meters (6,500 feet). When the base is at the surface, the phenomenon is essentially fog. The cloud sheet is generally featureless with a smooth underside.

Weather and effects: Stratus usually produces overcast skies and subdued lighting. If the layer is thick, it can yield light drizzle or mist; very thick layers may darken the day significantly. Visibility can be reduced, especially when the cloud base is low.

Types and relation: Stratus is part of the stratiform family of clouds and has several forms. Stratus nebulosus describes a uniform gray sheet with few features; Stratus opacus is a denser, darker variety; Stratus fractus refers to ragged, torn fragments formed by instability at the edges of a larger layer. Stratus can transition into related clouds such as nimbostratus when precipitation becomes more persistent, though that is classified separately.

Beyond meteorology, the term Stratus is sometimes used in branding and media to convey flatness or cloud-related ideas; this article concentrates on the atmospheric meaning.