Adiabatic heating occurs when air is compressed as it moves in which direction?

• A. Up a slope
• B. Down a slope
• C. Lateral flow
• D. Horizontally

Answer: (B)

Adiabatic heating happens when an air parcel is compressed, so its temperature rises without adding external heat. When air moves down a slope, it descends into higher ambient pressure, gets squeezed, and warms. This is the classic case of compression causing warming—the dry adiabatic heating rate is about 9.8 C per kilometer of descent. Conversely, rising air expands as pressure drops and cools, which is adiabatic cooling. Horizontal or lateral flow doesn’t inherently involve the vertical compression needed for adiabatic heating. So moving down a slope is the direction that produces adiabatic heating.