Explanation: The amount of water vapour in the atmosphere is added or withdrawn due to evaporation and condensation respectively.

• Evaporation is a process by which water is transformed from liquid to gaseous state. Heat is the main cause for evaporation.
• The temperature at which the water starts evaporating is referred to as the latent heat of vapourisation. The transformation of water vapour into water is called condensation.
• Condensation is caused by the loss of heat. When moist air is cooled, it may reach a level where its capacity to hold water vapour ceases.
• Then, the excess water vapour condenses into liquid form. If it directly condenses into solid form, it is known as sublimation.

Source: NCERT – India Physical Environment