The most frequent ground or surface-based temperature inversion is produced by which mechanism?

• A. Adiabatic cooling on a clear night
• B. Terrestrial radiation on a clear, relatively still night
• C. Industrial pollution in urban areas
• D. Moisture advection from over water

Answer: (B)

The most common surface temperature inversion is created by radiational cooling of the ground at night. When the sky is clear and winds are light, the ground loses heat to space by infrared radiation while there’s little mixing in the lowest air layer. The air in contact with the cool surface becomes cooler than the air above it, so the temperature increases with height in the near-surface layer, forming a stable inversion.

This explains why a clear, calm night is so conducive to surface inversions: clouds trap heat and winds mix the air, both of which reduce or prevent the strong nocturnal cooling that creates the inversion. Adiabatic cooling requires rising air, not just surface cooling; industrial pollution can cause localized inversions but isn’t the normal, widespread mechanism; moisture advection over water can lead to fog or humidity changes, not the typical surface-based inversion.