Which type of visibility is reported in the body of observations?

The prevailing visibility is the type of visibility that is reported in the body of observations. Prevailing visibility is defined as the greatest distance that can be seen in a particular direction and is typically determined by the distance at which objects can be clearly discerned. This measurement is critical for aviation operations as it provides pilots and air traffic controllers valuable information about the current visual environment.

In aviation weather reports, prevailing visibility is used because it represents the most relevant and consistent visibility condition that pilots and crew are likely to encounter while operating an aircraft. It reflects the visibility over a significant area and indicates the typical conditions experienced rather than any transient or localized visibility variations.

Ambient visibility, on the other hand, refers to the general visibility conditions in the area without specification, while variable visibility indicates that the visibility changes significantly in different directions, which may not provide a clear picture for aviation operations. Fixed visibility, while not a commonly used term in aviation weather reporting, suggests a static measurement, which does not align with the dynamic nature of meteorological conditions. Overall, prevailing visibility serves as the most pertinent and standardized measure for reporting visibility in aviation contexts.