In aviation weather, what does the term "ceiling" refer to?

The term "ceiling" in aviation weather specifically refers to the lowest layer of clouds above which visibility is unrestricted. This measurement is crucial for pilots as it indicates the vertical visibility conditions they can expect during flight operations. A cloud ceiling is particularly important during approaches and takeoffs, as it affects whether a pilot can fly visually or must rely on instrument flight rules (IFR).

An unrestricted visibility condition indicates that there are no significant obstructions to visibility beyond this cloud layer, allowing pilots to navigate safely. In contrast, other aspects of aviation weather, like cloud coverage or specific altitudes, do not define a ceiling's impact on visibility. This understanding is pivotal for safe flight operations, especially in varying weather conditions where low ceilings may necessitate alternate flying procedures.