Which layer of the atmosphere contains most of the atmospheric water vapor?

The troposphere is the layer of the atmosphere that contains the majority of atmospheric water vapor. This layer extends from the Earth's surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on geographic location and weather conditions.

Water vapor is essential for cloud formation, weather patterns, and the Earth's hydrological cycle. The density of air decreases with altitude, and since most of the air's mass, including water vapor, is concentrated in the troposphere, this is why it holds the greatest amount of water vapor compared to the other layers.

In the stratosphere, which sits above the troposphere, the air is much drier and contains very little water vapor. The exosphere, being the outermost layer, mainly consists of thinly dispersed hydrogen and helium, while the thermosphere, located above the mesosphere, experiences high temperatures but is also not a significant reservoir of water vapor. This atmospheric layering and the characteristics of each layer play a crucial role in climate science and meteorology.