Temperature inversion is most common in Mountain valleys.

Explanation:

Temperature inversion refers to a reversal of the normal atmospheric temperature gradient, where the temperature increases with altitude. In other words, instead of the temperature decreasing as we go higher in the atmosphere, it actually increases. This phenomenon is caused by the trapping of cool air near the surface of the Earth by a layer of warm air above it.

Inversions can occur in various locations, but they are most common in mountain valleys. Here's why:

1. Geographic Features:
- Mountain valleys are characterized by their topography, with high mountains surrounding a narrow valley floor.
- This topography plays a crucial role in the formation of temperature inversions.
- During the day, the sun heats up the valley floor, causing the air near the surface to warm and rise.
- However, at night, the valley floor cools rapidly due to radiative cooling, causing the air near the surface to become colder than the air above it.

2. Cold Air Drainage:
- In mountain valleys, cold air tends to drain down the slopes and accumulate in the valley bottom.
- This cold air becomes trapped beneath a layer of warmer air, leading to the formation of a temperature inversion.
- The surrounding mountains act as barriers, preventing the cold air from mixing with the warmer air above.

3. Stable Atmospheric Conditions:
- Temperature inversions are more likely to occur when the atmosphere is stable.
- In stable atmospheric conditions, there is little vertical mixing of air masses, allowing the inversion layer to persist.
- Mountain valleys often experience stable atmospheric conditions, especially during calm and clear nights when radiative cooling is most effective.

4. Local Climate:
- Mountain valleys tend to have specific climatic conditions that favor the formation of temperature inversions.
- The cool air trapped in the valley can lead to the accumulation of pollutants, such as smoke or fog, which further enhance the inversion layer.
- This can result in poor air quality and reduced visibility in these areas.

In conclusion, temperature inversions are most common in mountain valleys due to the geographic features, cold air drainage, stable atmospheric conditions, and local climate characteristics associated with these regions.