What is the difference between fog and clouds?

Clouds and fog both form when water vapor condenses. So what's the difference between them?

Transcript

00:00 Is there a difference between clouds and fog?

00:05 Physically speaking, no, because fog is nothing more than a cloud above the ground,

00:11 and both consist of tiny water droplets floating in the air.

00:16 These droplets are formed when water evaporates from lakes, rivers or oceans.

00:23 The water vapour cools as it rises and condenses.

00:28 The main difference between fog and clouds is how high they are.

00:34 If it's cold enough near the ground for water vapour to condense, it forms a visible mass.

00:40 This happens most in autumn and winter.

00:44 As soon as that mass of water vapour obstructs our ability to see beyond a kilometre away, we call it fog.

00:51 All other visible accumulations of water vapour are called clouds.

00:56 Scientists differentiate between a total of ten types, according to their altitude.

01:03 High-level clouds, also known as cirrus clouds, form at an altitude of 5 to 13 kilometres.

01:11 As it's very cold there, they're made up entirely of ice.

01:17 Middle clouds form between 2 and 7 kilometres above the ground.

01:22 These include a type of cloud known as altocumulus.

01:28 Low-level clouds occur below a height of 2 kilometres.

01:31 Some, like the stratus cloud, are so close to the ground that they're often referred to as high fog.

01:41 Vertical clouds extend over several layers, like for example the cumulus cloud,

01:46 which often looks like a cauliflower at the top.

01:52 More than half of the Earth's surface is typically covered by clouds.

01:57 And both clouds and fog play an important role in meteorology.

02:01 They regulate the Earth's water balance and have a big impact on the climate.

02:06 [Music]