How to Fly Helicopters

What is Fog?

We all know that fog keeps us on the ground when we want to be flying. But are you aware that there are different kinds of fog? Do you know the conditions that are required for fog to form? Do you know about radiation fog, advection fog, frontal fog, sea fog and hill fog?

This post should refresh your memory or perhaps even enlighten you.

Mist and fog occur when tiny water droplets are suspended in the air causing a reduction in visibility. Mist is very similar to fog and differs only by definition:

When the visibility is less than 1000m – FOG exists. Relative Humidity = 100%.

When there is reduced visibility but visibility is greater than 1000m – MIST exists. Relative humidity < 100%.

Water droplets come into existance due to condensation which causes the water vapour in the air to condense out as a liquid. This normally occurs when the air is cooled by an underlying cold surface or by the interaction of two air masses.

Different Types of Fog

There are three different types of fog and they form under specific conditions:

1. Radiation fog
2. Advection fog
3. Frontal fog

Radiation Fog

The conditions required for the formation of radiation fog are:

• Moist air – (high relative humidity) that only requires a small amount of cooling to reach its dewpoint temperature.