Why does fog form?
Show answer & explanation
Answer: Air cools and water condenses
Smoke mixes with moisture — Wrong. Fog is pure water droplets, not smoke. While pollution can make fog appear dirtier (smog), fog itself forms when water vapor condenses in cool air.
Air cools and water condenses ✓ — Correct! Fog forms when air cools to its dew point - the temperature where water vapor condenses into tiny droplets. This often happens at night when the ground cools, chilling the air above it. Millions of suspended water droplets scatter light, reducing visibility. Fog is basically a cloud at ground level!
Ice crystals float near surface — Wrong. Fog is made of liquid water droplets, not ice crystals. Ice fog can form in extremely cold conditions (below -30°C), but regular fog is liquid water suspended in air.
More Weather & Climate questions
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- Hail has clear and cloudy bands. Why not just 'up-down elevator rides'?
- Why is the coldest storm top not the best place for hail to grow?
- Why do supercells make 5-cm hail when ordinary storms usually cannot?