What mechanism primarily leads to the cooling of air during the night?

The cooling of air during the night is primarily due to radiation from the earth's surface. As the sun sets, the surface of the earth loses heat through a process known as longwave radiation. This occurs because the ground, which has absorbed solar energy during the day, emits infrared radiation, cooling down in the process. The cooling of the earth's surface then leads to the cooling of the air directly above it, as the air in contact with the ground loses heat to this cooler surface.

This process is crucial in understanding nocturnal temperature changes and is more significant than other mechanisms such as convection currents, which require movement of air and play a role in distributing heat rather than causing it. Conduction through the ground does contribute to heat transfer, but it is a slower and less impactful process compared to radiative cooling during the nighttime. Evaporation of moisture does absorb heat but is generally less prominent at night when the air's moisture might condense rather than evaporate, leading to less cooling in comparison to other processes.