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Meteorology

3.6.6.5 Shallow

Shallow fog is a layer of low fog that lies close to the ground and significantly

reduces visibility. Per definition Shallow fog is found less than 2 meters above

the ground.

Low fog can reduce visibility to less than 20 meters and can be extremely

dangerous due to its density. Visibility above this fog can be 1000 meters or

more. Visibility is measured in a height of 2 meters, and when low fog is below

2 meters the meteorological visibility can be mentioned as more than 10 km. If

RVR is reported, then it will show the low values in the low fog.

Low fog typically forms on cool nights or in the morning when moist air cools

to its dew point temperature.

Low fog is referred to as MIFG, and the English term is “Shallow fog.”

3.6.6.6 Sea smoke

In winter, when the air is very cold, fog can form over the sea, making it look as

if the sea is smoking.

The fog forms when the very cold air slowly blows over the warmer water. This

temperature difference causes water vapor in the air to condense, forming tiny

water droplets or ice crystals that float in the air. This concentration of small

droplets reduces visibility, but the phenomenon is generally not as dense as

fog.

Sea smoke is associated with reduced visibility and typically forms in the

morning or at night when

temperatures are lower

and humidity is higher.

Here you can see the

different types of fog and

how they form.

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Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 290