Question

Water vapour condenses to form drops of water higher up in the atmosphere. Why is the atmosphere cooler higher up?

Answer 1

The density of air decreases as we go higher up in the atmosphere. As the air becomes thinner, the temperature decreases. Moreover, the sun heats the surface of the earth due to which the lower atmosphere of the earth is also heated up. As we go up, the temperature decreases.
Hence, the atmosphere higher up is cooler as compared to the upper atmosphere.