Low level turbulence can occur and icing can become hazardous in which type of fog?

• A. Steam fog
• B. Radiation fog
• C. Advection fog
• D. Upslope fog

Answer: (A)

Steam fog forms when relatively warm, moist air moves over a cold water surface, causing evaporation and rapid saturation right at the surface. That creates a dense, shallow layer of fog, and the air just above and within it is often unstable with mixing and gusty motions. Those low-level air movements produce turbulence near the surface, which can surprise a pilot flying through the fog.

At the same time, the abundance of moisture in this fog means there are many liquid water droplets present. If the ambient temperature is near freezing, some of these droplets can be supercooled, so ice can start to form on the airframe when you fly through it. For a glider, icing reduces lift and worsens handling, and the combination of low-level turbulence with icing hazards makes steam fog particularly troublesome.

Radiation fog, advection fog, and upslope fog can all reduce visibility, but they’re typically less associated with the same combination of surface-based turbulence and icing risk present in steam fog.