What causes the temperature to increase with height through the stratosphere and decrease with height through the mesosphere?

In the stratosphere, temperature increases with height due to the absorption of ultraviolet (UV) radiation by the ozone layer, which warms this region. In contrast, the mesosphere sees a decrease in temperature with height because it is farther from the Earth’s surface and lacks significant heat sources, leading to less absorption of solar energy. As a result, the mesosphere is cooler, especially at its upper levels.