In METAR (Meteorological Aviation Routine) reports, "FG" is the abbreviation used to denote fog.
Fog is a type of obscuration, specifically a hydrometeor, that reduces visibility at the Earth's surface. In aviation, accurate reporting of fog is crucial for pilots to make informed decisions regarding take-off, landing, and enroute operations.
Here's a breakdown:
- METAR: A standardized format for reporting weather conditions, primarily used in aviation.
- FG: The METAR code for fog. When this code appears, it indicates that fog is present at the observation site.
- Obscuration: Fog is categorized as an obscuration because it reduces horizontal visibility. Other obscurations include mist (BR), sand (SA), and dust (DU).
- Hydrometeor: Fog is considered a hydrometeor because it is formed by the condensation of water vapor in the atmosphere.
The intensity of fog is typically indicated by modifiers preceding the "FG" abbreviation or through visibility reports included in the METAR. For example, "VCFG" might indicate fog in the vicinity, or a visibility of "1/4SM FG" would indicate a visibility of 1/4 statute mile due to fog.
