Fog

Advection Fog

Advection fog forms when warm, mosit and stable air is blown across a cooler surface (land or water). The air temperature falls until the dew point is reached and condensation occurs

Radiation Fog

Radiation fog is a thin layer that forms because land cools down overnight. When the dew point is reached, and condensation occurs the fog moves slowly upwards. Radiation fog is common at lakes, harbours and in river valleys

There are two types of fog formation processes: cooling the surface by radiation of heat and by advection of moist air over an already cool surface. In both cases air above the surface will cool to its dewpoint (RH 100%) but the way it does that is different as are the circumstances surrounding it.

For fog to form the temperature/dewpoint (T/Td) spread must be small enough or a RH of 100% will never be reached and an abundance of condensation nuclei must to be present too. These are the main factors.

Advection fog

This type forms when moist air moves over…