Explanation:
Water vapour is important for a number of different reasons, but its presence in the atmosphere is one of the most important. Water vapour is present within the atmosphere in varying amounts but is a vital component of the hydrologic cycle. In the atmosphere, water vapour can exist in trace amounts or even make up as much as 4% of the atmosphere. This concentration depends largely on where the water vapour levels are measured. On average, the value of water vapour in the atmosphere is 2-3%. In arid or very cold locations - such as polar regions - the amount of water vapour in the air is much lower.[4]
Even on a clear day, water vapour exists in the atmosphere as an invisible gas - unlike clouds which are droplets of liquid water that can be seen. If the conditions are right, water vapour in the air can collect on small particles of dust, salt, or smoke in the air to form small droplets. These droplets gradually increase in size and over time become various forms of precipitation. Since water vapour is so prominent in the atmosphere and forms precipitation, water vapour is a major component of the hydrologic cycle. When water holding areas are heated by the Sun, some of the water being held evaporates and becomes vapour, powering the cycle.[5]
In addition to being created by evaporating water, plants are capable of producing water vapour through a process of transpiration.
