In aviation weather reporting, what does FU represent?

In aviation weather reporting, FU specifically represents smoke. This designation is part of the aviation weather code used in METAR (Meteorological Aerodrome Report) and TAF (Terminal Aerodrome Forecast) reports. Smoke can significantly impact visibility and may affect flight operations, making it essential for pilots and air traffic controllers to be aware of its presence.

The other options do not have corresponding meanings within the standard aviation weather reporting framework. For instance, while fog is indeed a relevant weather phenomenon, it is denoted by the code "FG," not FU. Additionally, there is no standardized measurement for fungal units or a specific representation for funnel clouds in aviation weather reporting. Thus, understanding that FU stands for smoke is crucial for accurate interpretation of aviation weather conditions.