The meteorological term denotes the height above the Earth’s surface of the lowest layer of clouds or obscurations reported as “broken” or “overcast,” or the vertical visibility into an obscuration. This height is a critical factor in determining the usability of an airfield for aircraft operations. For example, a pilot planning a visual flight rules (VFR) flight needs to ensure that the prevailing conditions meet or exceed the minimum height requirements for cloud clearance.
Understanding this altitude is essential for flight safety and efficient air traffic management. It directly impacts departure and arrival procedures, influencing decisions regarding alternate airports and instrument approaches. Historically, inaccurate or unavailable measurements of this parameter have contributed to aviation incidents. Improved technology and observation techniques have enhanced the accuracy of reported values, leading to safer and more reliable air travel.