What do the numbers in a vertical visibility indication refer to in a TAF?

The vertical visibility indication in a TAF (Terminal Aerodrome Forecast) specifically refers to the height above the ground in hundreds of feet. This measurement is critical for pilots as it informs them of how high they can see vertically, especially in conditions where visibility might be restricted due to weather phenomena like fog or low clouds. When the vertical visibility is expressed in this format, it directly communicates the altitude limit of visual perception, allowing flight crews to make informed decisions regarding approach and landing phases of flight.

This understanding is essential because knowing the vertical visibility can help pilots assess whether they can safely operate under visual flight rules (VFR) or if they need to rely on instruments due to restricted visual conditions. The other options, while relevant to aviation weather concepts, do not accurately describe the purpose of vertical visibility in a TAF. Hence, the reference to height in hundreds of feet is the correct interpretation.