Spaatz Aerospace Practice Test 2025 – The All-In-One Guide to Master Your Exam!

Radiation fog forms through the cooling of moist air during the night, which occurs when the ground loses heat through radiation. As the ground cools, the air in contact with it also cools, leading to a decrease in its ability to hold moisture. Once the air temperature drops to the dew point, condensation occurs, resulting in fog. This type of fog is most commonly observed in low-lying areas after clear, calm nights when humidity levels are high, and it typically dissipates with the warming of the air after sunrise.

The other types of fog listed do not form primarily due to nighttime cooling of moist air. Advection fog happens when warm, moist air moves horizontally over a cooler surface, leading to cooling and condensation. High-inversion fog forms in stable air where temperature inversions trap moisture beneath a layer of warmer air. Upslope fog is created when air rises along terrain and cools due to adiabatic expansion, which does not specifically relate to nighttime cooling. Thus, radiation fog is the correct answer due to its clear association with the cooling of moist air during the night.