Observing Cloud Height
Some tips for determining the height of clouds.
You may also find a Dichotomous
Key for Cloud Identification (developed by Dr. Tina Cartwright) helpful for this.
An excellent web resource for background on observing clouds is
These are generally clouds made of water droplets whose base is below 2 km
altitude (they can be made of ice when the temperature is cold enough, for
example at high latitudes in the winter-time). Cloud types include
stratocumulus, cumulus, stratus, cumulonimbus and nimbostratus. Fog can also
be put in this class.
If you think these type of clouds are present there are some
measurements you can make to estimate the altitude
of the cloud base.
For the CERES project, we define mid-level clouds as those whose base is
between 2 and 6 km altitude. Cloud types are altostratus or altocumulus, and
are generally but not always water clouds, depending on the atmosphere's
temperature and other conditions at the cloud altitude.
High clouds are those whose base is above 6 km. Types include cirrus,
cirrocumulus and cirrostratus. These clouds can be either ice or water
particles, but are more often ice. Water clouds tend to have definite edges,
while ice clouds are more wispy. Persistent contrails (airplane tracks
that don't just disappear as the airplane passes) are high clouds as well,
and should be included as part of the observation. When you see contrails,
please note their presence by checking the box on the report form.
Multiple cloud layers
There is often more than one cloud layer present, and if the lower layer is
broken this can be observed from the ground. When this is the case, we would
like to know what combination was present: low+mid, low+high, mid+high, or
low+mid+high. It is understood that when solid cloud is present, a layer
above it will not be observable from the ground.
Comment from the Field
Typically there are no points of reference in the sky's blue background to
determine cloud height and we depend on identifying the cloud type to
determine the altitude of the clouds observed.
This comment from the Cliffs of Dover, UK, on December 3, 2001, provides an
example of a location with some unique points of reference in determining
low level cloud altitudes fairly accurately.
"...Very gloomy day - lights needed on all day in the classroom. Cloud base no
higher than about 600 feet above sea level. By the time of the second pass of
the satellite at 1227UTC the cloud base was down to about 200 feet above sea
level and visibility was down to about 2km. We are able to judge cloud base
as we are about 300 feet above sea level, and can also see Dover Castle on
the next hill, about a mile away. It is slightly higher than us and by it
there are three tall radio masts - as they all gradually disappear
from view we can judge the altitude of the cloud base!..."
View this and other reported cloud observations on the
Select Date - December 3, 2001 to view this observation along with the others
made at various sites that day.
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