Which type of frost is driven by cold air moving in from very cold regions?

• A. Radiative frost
• B. Advective frost
• C. Hail frost
• D. Smog frost

Answer: (B)

This item tests how frost forms when the cause is cold air movement versus surface heat loss. Advective frost happens when a mass of very cold air moves horizontally into an area from polar or high-latitude regions. That cold air blankets the surface, and the near-surface temperatures fall below freezing, so frost forms on exposed surfaces as the air mass sits over the area. It’s driven by the movement of the air itself, not by the ground losing heat to the sky.

In contrast, radiative frost forms on clear, calm nights when the ground loses heat directly to the night sky. The surface cools even if the air isn’t being brought in from elsewhere. Hail frost and smog frost describe frost occurring under different, less typical circumstances (hail-related weather events or polluted air trapping heat and altering cooling), but they don’t define frost formation through the horizontal movement of an extremely cold air mass.