FAA Aircraft Dispatcher Practice Exam

What is defined as Radiation fog?

1. Fog that forms over lakes

2. Fog that forms in clear, calm conditions

3. Fog resulting from moist air over warm ground

4. Fog that occurs only in winter

The correct answer is: Fog that forms in clear, calm conditions

Radiation fog is specifically characterized by its formation in clear, calm conditions, typically during the night and early morning hours. This type of fog occurs when the ground loses heat rapidly through radiation, causing the air close to the surface to cool. When the air temperature drops to its dew point, moisture in the air condenses into tiny water droplets, creating fog. Understanding the formation process clarifies why conditions such as a lack of wind and clear skies are essential for radiation fog. The calmness allows for the collected cool air to remain undisturbed, facilitating this unique cooling and condensation process. Thus, the description of fog that forms in clear, calm conditions accurately captures the essence of radiation fog's occurrence. In contrast, fog that forms over lakes typically relates to different atmospheric conditions, while moisture over warm ground does not align with the cooling processes involved in radiation fog. Additionally, although radiation fog can occur in winter, it is not limited to this season, ruling out that particular definition.