Air masses can extend up to...

• A. Only a few kilometers above the surface.
• B. The lower troposphere.
• C. The top of the troposphere.
• D. Into the stratosphere.

Answer: (C)

Air masses are large, horizontally uniform bodies of air that form over regions with relatively stable surface conditions, and they mix well throughout the troposphere where weather happens. The boundary between the troposphere and the stratosphere is the tropopause, which acts like a ceiling that limits vertical mixing. Because of that, an air mass typically extends through the entire troposphere up to its top, rather than just a shallow layer or reaching into the stratosphere. The exact height of the troposphere varies with latitude and season (roughly about 8 km at the poles to 16–18 km near the equator), but the top of the troposphere is the general vertical limit for an air mass.