The layer in the atmosphere that contains the most water vapor and gases is the troposphere.
The troposphere is the lowest layer of Earth’s atmosphere, extending from the surface up to about 8 to 15 kilometers (5 to 9 miles) in altitude, depending on the geographical location and weather conditions. This layer is where most of our weather occurs and holds approximately 75% of the atmosphere’s total mass, including the majority of its water vapor.
As you ascend through the troposphere, the temperature generally decreases, leading to the formation of clouds and precipitation. Since temperature plays a significant role in the capacity of air to hold moisture, the troposphere’s warmer conditions near the surface allow it to accommodate a higher concentration of water vapor and various gases compared to the layers above.
In summary, the troposphere is not only vital for weather patterns but also serves as the reservoir for most of the water vapor and gases present in the atmosphere.