Advection Hoar Frost
(Section 3.2.1.4.4)Definition: Advection hoar frost: A deposit of ice that generally assumes crystalline form and which forms on objects, the surface of which is sufficiently cold to bring about deposition of the water vapour contained in the air coming into contact with this surface, usually through a process of advection.
Advection hoar frost is deposited mainly on vertical exposed surfaces. It is observed when relatively warm damp air suddenly invades a region where the temperature of the exposed surfaces is below 0 °C and below the frost-point of the advected air.