What atmospheric condition can lead to suppression of turbulence and mixing at night?

Radiative cooling is the correct choice because it describes the process in which the Earth's surface loses heat through the emission of infrared radiation during the night. As the surface cools, it can lead to the formation of a stable thermal inversion, where warmer air traps cooler air near the surface. This stability suppresses turbulence and mixing in the atmosphere, leading to a more stratified layer.

In contrast, increased humidity can actually enhance turbulence in the atmosphere since moist air can lead to more convective activity. Nighttime wind speeds can also disrupt stratification and increase mixing, while low air pressure alone doesn't directly contribute to the suppression of turbulence and mixing at night. Instead, it is the cooling of the surface, characteristic of radiative cooling, that primarily results in stable atmospheric conditions and suppression of turbulence.