What type of fog is commonly seen on calm, clear, cool nights?

Radiation fog is commonly associated with calm, clear, and cool nights. This type of fog typically forms when the ground loses heat quickly through radiation, which cools the air immediately above the surface to its dew point. On calm nights, there are no winds or other atmospheric disturbances that would mix the air layers, allowing the colder air to settle near the ground. As a result, moisture condenses in the cooler air to form fog.

In this scenario, the temperature drops, and under the right humidity conditions, the cooling effect can lead to the development of fog, which is often dense and can significantly reduce visibility. Understanding radiation fog is important for both pilots and dispatchers as it can impact flight operations during nighttime hours.