Study on Visibility Changes during Fog Occurrence Using High Frequency Observational Data

Fog reduces visibility and significantly affects aircraft operations at airfields. Therefore, forecasters must predict the onset of fog at minute-level resolutions. However, current numerical weather prediction (NWP) models cannot meet this requirement, and empirical forecasting rules based on past events remain essential. In this study, we aimed to clarify the patterns of visibility change associated with different fog types. We used high temporal resolution observations collected at airfields along the Pacific coast of Japan. The results showed visibility transitions before fog onset and during fog dissipation depending on fog type. Precipitation fog exhibits gradual changes in visibility, whereas advection and radiation fogs tend to show more abrupt transitions. The time range for Special Visual Flight Rules (SVFR), during which rapid flight operations are required, also varies by fog type: approximately 4 h for precipitation fog and approximately 2 h for advection and radiation fog. These findings contribute to improving fog forecasting at airfields and support aviation decision-making, particularly for aircraft operations under visual flight rules.