Comprehensive Study Notes on Fog Types for Pilots

Fog is defined as a low-lying cloud consisting of tiny water droplets that are near the Earth's surface.
It causes reduced visibility, impacting visual flying conditions.
Fog forms when air temperature reaches the dew point, leading to water vapor condensing into visible droplets.
Fog versus Mist:
- Fog results when visibility is less than 5/8 statute mile.
- Mist occurs when visibility is greater than 5/8 statute mile.

Formation: Often occurs at night when the surface cools, causing the air above to cool as well.
If the air contains enough moisture, this cooling leads to saturation and fog formation.
Alternative Name: Known as ground fog if it's less than 20 feet thick.
Time of Occurrence: Common in early mornings and dissipates soon after sunrise as the ground warms.
Contributing Conditions:
- Clear skies allow maximum cooling since clouds trap heat.
- Calm winds enable uninterrupted cooling of the air.
- Long nights (often in winter) allow prolonged cooling periods.
Associated Weather Systems: High-pressure systems often create conditions favorable for radiation fog.

Formation: Occurs when warm, moist air moves over cooler ground or water.
Features: Typically shallow and associated with temperature inversions.
Unlike radiation fog, advection fog can form with strong winds and under cloud cover.

Formation: Develops when moist air is forced upward over rising terrain, cooling adiabatically (a process where the temperature decreases as air rises).
Characteristics: More common at higher elevations; can build down into valleys.
Conditions: Can occur in high wind conditions due to increased lift and cooling.

Also Known As: Evaporation fog.
Formation: Occurs when cold air moves over a warmer body of water; warm water evaporates into cooler air.
Visual Characteristics: Appears as wispy tendrils rising from the water's surface, resembling steam.
Common Occurrence: Often seen in early fall or late spring when air temperature drops rapidly compared to water temperature.

Formation: Develops in saturated air when surface temperatures fall below freezing.
Droplet Type: Contains supercooled water droplets, which are liquid despite subzero temperatures due to lack of ice nuclei.
Common Areas: More prevalent in cold winter regions, particularly in stagnant cold air valleys.
Impact: Supercooled droplets freeze upon contact, forming rime ice on surfaces.

Comparison to Freezing Fog: Consists of tiny ice crystals and occurs in extremely cold conditions (well below 32°F or 0°C).
Composition: Unlike freezing fog, ice fog is comprised of ice crystals instead of supercooled droplets.

Formation: Develops during the passage of warm or cold fronts as rain falls through colder air and evaporates, raising the dew point and causing saturation.
Variations: Fog associated with warm fronts is termed prefrontal, while fog associated with cold fronts is post-frontal.
Behavior: Frontal fog tends to dissipate shortly after the front passes.

Formation: Occurs when rain falls through cold, dry air, increasing moisture and raising the dew point, leading to saturation and fog formation.
Association: Typically linked with frontal systems and can form from slower-moving cold fronts.

Fog is particularly troublesome for VFR (visual flight rules) flying due to significantly impaired visibility.
IFR (instrument flight rules) flying is less severely affected, as pilots rely on instruments rather than visual cues.

Understanding the types and conditions associated with fog is crucial for pilots to ensure safety in varied flying conditions.
The knowledge of how to identify and anticipate fog formation can help in flight planning and risk management during flights.