FAA Ground School Practice Test

What weather conditions are expected beneath a low-level temperature inversion layer with high relative humidity?

1. Strong winds and clear skies

2. Heavy precipitation and fog

3. Smooth air, poor visibility, fog, haze, or low clouds

4. Cold temperatures and high visibility

The correct answer is: Smooth air, poor visibility, fog, haze, or low clouds

Beneath a low-level temperature inversion layer with high relative humidity, the conditions tend to be stable, leading to a lack of vertical mixing in the atmosphere. This stability traps cooler, moist air close to the ground, which can result in reduced visibility due to the presence of fog, haze, or low clouds. The high relative humidity indicates that the air is saturated or nearly saturated, promoting the formation of these moisture-related phenomena. Smooth air can be expected because the stability reduces turbulence, resulting in calmer conditions. Therefore, the combination of these factors creates a scenario where visibility is poor, and moisture manifests as fog, haze, or low clouds, making it difficult for pilots to see clearly. This understanding of how temperature inversions affect weather conditions is crucial for flight planning and safety, recognizing that such inversions can sometimes lead to significant challenges for aircraft operations.