The troposphere contains about three quarters of the mass of the entire atmosphere. The troposphere is only 12 km thick while the whole atmosphere is about 120 km thick. Explain why the troposphere contains such a large fraction of the total mass.

Key Concepts

Atmospheric Composition

The atmosphere is composed of various gases, primarily nitrogen (78%) and oxygen (21%), with trace amounts of other gases. The distribution of these gases is not uniform; most of the mass is concentrated in the lower layers, particularly the troposphere, due to gravitational forces that hold denser gases closer to the Earth's surface.

Pressure and Density

Atmospheric pressure decreases with altitude, leading to a corresponding decrease in gas density. In the troposphere, the pressure is highest, resulting in greater density and, consequently, a larger mass of air. This phenomenon explains why the troposphere, despite its relatively small thickness, contains a significant portion of the atmosphere's total mass.

Temperature Gradient

The troposphere experiences a temperature decrease with altitude, which affects the behavior of air molecules. Warmer air at lower altitudes is less dense and can hold more moisture, contributing to the mass of the troposphere. This temperature gradient helps maintain a stable layer of air that retains most of the atmosphere's mass.