What best describes the cause of katabatic winds?

What best describes the cause of katabatic winds?

• A. Cooling air on mountain slopes becomes dense and flows downslope.
• B. Heating air at the surface creates upward convection.
• C. Jet streams aloft push air down into valleys.
• D. Moist air descends into valleys forming a stable layer.

Answer: (A)

Katabatic winds are caused by cooling air along mountain slopes becoming denser than the air nearby and then flowing downslope under gravity. After sunset or in clear, calm conditions, radiative cooling cools the air near the slopes. The denser air then drains downhill, creating a downslope wind that can accelerate as it moves into valleys. This matches the idea of cooling air on mountain slopes becoming dense and flowing downslope. The other ideas describe different processes: heating air at the surface drives upward convection (not a downslope drainage), jet streams aloft influence large-scale flow rather than a local slope drainage, and moist air descending to form a stable layer describes a subsidence situation not the gravity-driven downslope flow along terrain.

Katabatic winds are caused by cooling air along mountain slopes becoming denser than the air nearby and then flowing downslope under gravity. After sunset or in clear, calm conditions, radiative cooling cools the air near the slopes. The denser air then drains downhill, creating a downslope wind that can accelerate as it moves into valleys.

This matches the idea of cooling air on mountain slopes becoming dense and flowing downslope. The other ideas describe different processes: heating air at the surface drives upward convection (not a downslope drainage), jet streams aloft influence large-scale flow rather than a local slope drainage, and moist air descending to form a stable layer describes a subsidence situation not the gravity-driven downslope flow along terrain.