Why is the temperature of stratosphere increases with height?

The temperature of the stratosphere increases with height primarily due to the absorption of ultraviolet (UV) radiation from the sun by the ozone layer, which is concentrated in this atmospheric layer. As UV radiation is absorbed, it warms the surrounding air, leading to a temperature increase with altitude. This temperature inversion is in contrast to the troposphere below, where temperature decreases with height due to the decreasing pressure and density of the air.