Cloud the bottom of the hierarchy. Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis. They are given below in approximate ascending order of instability or convective activity. "Non-convective" stratiform clouds appear in "stable" airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere. The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level). Fog is commonly considered a surface-based cloud layer. The fog may form
One sheet One sheet In the entertainment industry, a one-sheet or one sheet is a single document that summarizes a product for publicity and sales. A one sheet is a specific size (typically before 1985; after 1985) of film poster advertising. Multiple one-sheets are used to assemble larger advertisements, which are referred to by their sheet count, including 24-sheet billboards, and 30-sheet billboards. The term is also used as synonym for the poster artwork and the film poster itself. Since a one-sheet is used in the official advertising for films, they are prized by both collectors of memorabilia for specific films and