Explanation for the variation of temperature with altitude

The upper reaches of the atmosphere (the thermosphere) are very hot due to absorbtion of short wavelength ultra violet radiation by oxygen molecules and subsequent reactions.

This photochemical cycle effectively transforms light into heat.

No significant build up of ozone occurs because the short wavelength ultra violet radiation present in this region of the atmosphere destroys ozone almost immediately.

The mesosphere is comparatively cool because it does not contain much material to absorb light and because most of the very high energy radiation from the Sun has been absorbed in the thermosphere.

The stratosphere is warmer than the mesosphere because it contains a higher density of particles and these are more effective at absorbing ultra violet radiation than the low pressure gas in the mesosphere.

The resulting photochemical cycle leads to the generation of ozone and the transformation of light into heat.

Ozone is also destroyed by sunlight, but this process is slow enough to allow a reasonable concentration of ozone (10 ppmv) to accumulate.

The upper troposphere is cooler than the stratosphere because most of the ultra violet radiation has already been absorbed in the stratosphere.

The remaining ultra violet radiation together with visible and infra red radiation arrives at the Earth's surface and is absorbed causing warming of the surface layer of rock and water. The warm surface layer re-radiates warmth and convection currents carry this heat energy up into the troposphere. Consequently, the temperature of the troposphere decreases with altitude.

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