Clouds and Fog
 Clouds are obvious indicators of weather and weather systems.
 Clouds are formed by very small droplets of condensed water.
 Precipitation does not fall from all clouds because the droplets need to be
somewhat large for gravity to pull the drops toward the earth. Thousands of
these tiny droplets would have to join together.
3 Types of Cloud Formations
Convective Clouds – produced when air near the ground warms up due to heated
surfaces (oceans, lakes, asphalt, concrete, dirt), becomes warmer
and less dense, and rises in the atmosphere, taking the water
vapour with it.
Frontal Clouds – form when two masses of air, with different temperatures, meet one
another.
Orographic Clouds – form when air moves up a mountain, expands at low pressure and
cools.
Fog
 Fog is a cloud that forms near the ground.
 It is produced when the air near the ground cools, allowing water vapour to
condense into fog.
Classifying Clouds
There are two general shapes of clouds:
Cumulus Clouds – heaping rounded shape. Grow vertically and usually indicate unstable
weather.
Stratus Clouds– have a spread out, flattened, layered shape. Grow horizontally and
tend to indicate stable weather.
Cloud Group
Cloud Base Height
Cloud Types
High Clouds
tropics: 6000-18000m
mid-latitudes: 5000-13000m
polar region: 3000-8000m
Cirrus
Cirrocumulus
Cirrostratus
Middle Clouds
tropics: 2000-8000m
mid-latitudes: 2000-7000m
polar region: 2000-4000m
Altostratus
Altocumulus
Low Clouds
tropics: surface-2000m
mid-latitudes: surface-2000m
polar region: surface-2000m
Stratus
Stratocumulus
Nimbostratus
Clouds with Vertical
Growth
tropics: up to 12000m
mid-latitudes: up to 12000m
polar region: up to 12000m
Cumulus
Cumulonimbus
Cirrus Cloud
Stratus Clouds
Cirrostratus Clouds
Cirrocumulus Clouds
Altostratus Cloud
Altocumulus Clouds
Stratocumulus Cloud
Nimbostratus Cloud
Cumulus Cloud
Cumulonimbus Clouds