Water vapor in the atmosphere...?

Question

What is its purpose?

Answer 1

Water vapour in the atmosphere plays an important role in Meteorology.Not only that it affects the temperature of a place,aiding as a trap for radiation,and moderating the climate of a place but it is also responsible for the formation of a number of meteorological elements, known as hydrometers and photometers.Hydrometers include falling particles like rain and snow, suspended particles like cloud,fog etc,and particles deposited on the earth like dew, hoar-frost etc.Photometers include halo,carona,rainbow etc.The presence of water vapour in the atmosphere imparts a different nature to it -known as humidity.Therefore when the water vapour is present,the air is said to be humid,- otherwise it is dry.The water vapour mixed with air behaves like a gas.It contributes its own pressure to the total pressure of the atmosphere.It aids in the formation of thunder clouds and cyclones also.Water vapour is powerful absorber of heat radiation that is emitted by the earth's surface.Hence it traps the radiation when there is a cloud cover and leads to what is known as 'Greenhouse Effect".

Answer 2

What do you mean? Why did God put it there?

Water evaporates and exists as water vapor in the atmosphere. There is no purpose, it just is.

Water vapor in the atmosphere has many effects on the weather, if that is what you are getting at. It serves as a greenhouse gas, thus keeping the planet warmer. Obviously without water vapor there would be no clouds or rain. The latent heat released by water vapor when it condenses contributes to the immense power of thunderstorms, tornadoes, and hurricanes.

Answer 3

the water vapour in the atmasphere is due to the evapouration of the water from various sources.
its main use is to maintain the water cycle of earth.

and also to cause rains.