What is a cold front?

What is a cold front?

• A. A front formed by warm air rising over cold air
• B. The surface expression when cold air displaces warm air
• C. A warm air pocket advancing over cold air
• D. A high-pressure boundary

Answer: (B)

A cold front is the boundary where a mass of cold air advances into and displaces warmer air at the surface, causing the warmer air to rise. This surface interaction—cold air moving in and pushing the warm air out of the way—best describes what a cold front is. The other scenarios describe warm-front dynamics (warm air rising over cold air) or a boundary not defined by a temperature contrast (a high-pressure boundary), which is why they don’t fit a cold front.

A cold front is the boundary where a mass of cold air advances into and displaces warmer air at the surface, causing the warmer air to rise. This surface interaction—cold air moving in and pushing the warm air out of the way—best describes what a cold front is. The other scenarios describe warm-front dynamics (warm air rising over cold air) or a boundary not defined by a temperature contrast (a high-pressure boundary), which is why they don’t fit a cold front.