Which term describes the visibility in a specified sector?

The correct term that describes visibility in a specified sector is indeed referred to as "Sector visibility." In aviation meteorology, sector visibility is specifically used to indicate the visibility conditions that are observed or reported within a particular angle or direction. This is particularly important for pilots and air traffic controllers, as it helps assess conditions in specific flight paths or approach routes.

Prevailing visibility pertains to the greatest distance at which objects can be seen and identified throughout at least half the horizon circle. This measure does not limit visibility to specific sectors but considers the overall visibility.

Variable visibility refers to visibility that changes over short periods, which does not specifically address the concept of sector visibility.

Runway Visual Range (RVR) is a specific measurement used to define visibility along a runway, particularly for takeoff and landing, but again, it is not specifically tied to varying visibility within a defined sector.

Therefore, the categorization of visibility into sectors is appropriate and aids in making precise and safe navigation decisions.