The lowest layer of the atmosphere is called the troposphere. The boundary layer between the troposphere and the stratosphere is called the tropopause.
The troposphere is the layer where we live, where all weather is found. It has water vapor and clouds. The thickness of the troposphere depends upon a number of atmospheric variables at latitude. The troposphere ranges from a thickness of approximately 5.5 mi (9 km) in the polar regions, to a thickness of approximately 10 mi (16 km) in equatorial regions
The tropopause is the boundary layer in the Earth's atmosphere between the troposphere and the stratosphere. It is a thermodynamic gradient stratification layer, marking the end of the troposphere. It lies, on average, at 17 kilometers (11 mi) above equatorial regions, and about 9 kilometers (5.6 mi) over the polar regions.