|SAT: DETERMINING CLOUD HEIGHT AND TYPE
METEOROLOGIST JEFF HABY
On satellite, it can be easy to find the clouds and clear regions but more difficult to determine
cloud height and type.
Cloud height can be inferred by the cloud temperature on infrared imagery. A good idea is to divide the
troposphere up in your mind into three layers: low levels (surface to 700 mb), middle levels
(700 mb to 500 mb) and upper levels (above 500 mb). Low clouds on Infrared imagery will have a darker
shade since they are relatively warm. In fact, clouds that are about the same temperature as the surface can be
very difficult to detect. Thus, low clouds are pretty easy to determine by looking at infrared imagery if they
have a different temperature as compared to the ground surface.
The middle level clouds will be colder and thus more white on infrared imagery. Sometimes it can
be difficult to distinguish between a middle and upper level cloud, with the exception of thunderstorms. When the
cloud is a thunderstorm or thunderstorm complex it is very noticeable since the cloud tops are very
cold with overshooting tops and cirrus blow-off. Thus, the tops of thunderstorm clouds are easy to
notice on satellite.
Here are how the different cloud types look on satellite imagery:
Fair Weather Cumulus: A darker shade on infrared imagery since they are close to surface. On visible they
look like a field on white bubbles with space between each white blob. Since this clouds have plenty of
moisture they are usually fairly white on visible.
Low level Stratus: Dark on infrared since these clouds are relatively warm. They often spread over a
wide area. On visible they are fairly reflective and thus fairly white. Since they are stratus clouds
they have a much smoother appearance as compared to thunderstorm clouds.
Altostratus / Nimbostratus: They are colder than low level stratus thus they are whiter on infrared imagery. They are
fairly white on visible imagery.
Altocumulus: Look similar to altostratus but are more globular.
Thunderstorm Clouds: Very bright white on infrared and visible imagery since the cloud tops are
very cold and the clouds are very thick. They are texture on visible due to the shadows being
cast. Overshooting tops show up very cold on infrared. Often an anvil with anvil blow off from the
upper level winds can be seen.
Cirrus: Just like they look wispy in person from the ground they can look thin and wispy on
visible imagery also. If the cirrus are thin enough they might not be seen at all on satellite
imagery. Cirrus clouds are very cold. However, since they are often thin also they sometimes do
not show up on infrared as well as one might think. If they are thick though they will show up
very well on infrared as bright white clouds.
Fog: Often has edges along elevated surfaces on visible imagery and often forms over
wet areas. Fog likes to develop in valleys. On infrared it can be difficult to see since the
temperature is about the same as the surface. On visible though they will be white like any