How is visibility measured when it falls on undefined boundaries in reporting?

Visibility measurement in meteorological reporting is critical, particularly when it falls on undefined boundaries. It is typically assessed using defined parameters set by standards in weather observation. When visibility is affected by transparency that does not clearly delineate between two ranges, the standard procedure is to report it by the lower defined boundary.

This approach ensures that measurements remain consistent and standardized across different observational contexts. By utilizing the lower boundary, meteorologists account for cumulative phenomena such as fog or precipitation that may limit visibility, thereby providing a more conservative estimate. This method is crucial to ensure safety, as reporting a visibility distance that adheres to the lower boundary helps to communicate worst-case scenarios effectively.

In contrast, using the higher boundary could potentially mislead about actual conditions, encouraging activities that might not be safe, especially in aviation or marine operations where visibility is critical. Similarly, while visual observation is part of the overall assessment process, it does not directly dictate the reporting standard for undefined visibility boundaries, which is why the lower defined boundary method is preferred.