Question 1 of 15
What technically distinguishes fog from mist?
Why: Fog is defined by visibility under 1 km (0.62 mi); mist is anything above.
Question 2 of 15
What is a fog?
Why: Fog is essentially a stratus cloud at ground level.
Question 3 of 15
What causes 'radiation fog'?
Why: On clear calm nights the surface cools, chilling the air above until it saturates.
Question 4 of 15
What causes 'advection fog'?
Why: Common over San Francisco Bay in summer.
Question 5 of 15
What is 'freezing fog'?
Why: Coats surfaces in rime; a major highway hazard.
Question 6 of 15
What is 'ice fog'?
Why: Ice fog forms at very cold temperatures (below -30°C).
Question 7 of 15
What is 'sea smoke'?
Why: Cold arctic air over relatively warm water produces steaming, wispy 'sea smoke'.
Question 8 of 15
Which US city is famous for its persistent summer fog?
Why: SF Bay area advection fog is a defining feature of its climate.
Question 9 of 15
What is 'valley fog'?
Why: Cold air drains downslope at night and condenses in low areas.
Question 10 of 15
What causes 'upslope fog'?
Why: Common on the eastern slopes of the Rockies.
Question 11 of 15
How much water is in a typical fog?
Why: Fog is actually quite thin — about 0.05 g of water per cubic meter.
Question 12 of 15
Which country installs 'fog fences' to harvest water?
Why: Chilean coastal communities collect drinking water from fog with mesh screens.
Question 13 of 15
What weather condition often produces valley fog?
Why: Radiational cooling with light wind concentrates humidity in low areas.
Question 14 of 15
What is 'flash fog'?
Why: Rapid dew point change can spawn fog in minutes.
Question 15 of 15
Which airport in the US has the most fog delays?
Why: San Francisco's marine layer is a leading cause of west-coast delays.