What is it called when temperature first increases with height and then begins to decrease?

The situation described, where temperature first increases with height and then begins to decrease, is referred to as a temperature inversion. This atmospheric phenomenon occurs when the temperature gradient deviates from the usual decrease in temperature with elevation. During a temperature inversion, warm air traps cooler air near the ground, which can have significant impacts on weather and air quality.

This knowledge is essential in meteorology because inversions can lead to the formation of fog and smog, and they can also affect the dispersion of pollutants. Additionally, temperature inversions can impact aviation by influencing local weather conditions.

In contrast, the other terms listed describe different atmospheric phenomena. Subrefraction and superrefraction pertain to the bending of light rays in the atmosphere, while atmospheric refraction refers to the change in the direction of waves due to a change in their speed in different mediums, neither of which directly relates to the concept of temperature gradients. Understanding temperature inversions is crucial for studying how temperature changes affect various atmospheric processes.