How does temperature change with altitude in the troposphere?

In the troposphere, temperature generally decreases with altitude. This trend occurs because the Earth's surface absorbs sunlight and warms up, which in turn warms the air above it through conduction. As one moves higher in the troposphere, the air is less densely packed and further from the heat source of the Earth's surface, leading to a decline in temperature. This decrease occurs at an average rate of about 6.5 degrees Celsius for every kilometer of ascent, known as the environmental lapse rate.

This behavior is foundational in meteorology, as it influences weather patterns, cloud formation, and atmospheric stability. In contrast, the other options do not accurately represent the behavior of air temperature in the troposphere: it does not remain constant, it does not increase with altitude, and while temperature can indeed exhibit short-term variations, the overall trend is a decrease with height. Thus, understanding this temperature profile is crucial for predicting weather and atmospheric phenomena.