CL O U D CL A S S I F I C AT I O N
Your group will be provided with two or three polar-orbiting satellite
images and a corresponding number of US outline maps. If you
have a ground station, your teacher will help you locate images
stored on the computer. Use the following criteria to help you in
your classification of clouds.
HIGH CLOUDS
Th ese clouds are generally found between 6 and 12 km. Th ey are composed primarily of ice, and
appear bright white on infrared imagery. Two examples are towering cumulonimbus and cirrus.
Cumulonimbus appear as bright white splotches, and are often associated with thunderstorm activity.
Cirrus clouds appear as bright white streaks - as if they had been painted by a brush.
MIDDLE CLOUDS
Heights are generally between 2 and 6 km. These appear as a lighter shade of gray than the surface
or low-level clouds on infrared images. Two examples are altocumulus and altostratus. Th e former
will have a mottled texture while the latter will appear more sheet-like. Be aware that the middle level
clo uds are usually the hardest to determine since they areoften shielded by higher level clouds.
LOW CLOUDS
Heights generally do not exceed 2 km. Two of the lowest clouds are stratus and fog. On the infrared
ima ge, they appear in a uniform dark gray shade and lack any texture. Often they are hard to
distinguish from the ground because of similarities in temperature.
12 km
6 km
2 km
- In this activity, clouds are classified according to height (low, me dium, high). Why is this classification method used
instead of another?
- Are there any areas on your maps where precipitation may be occurring? Which map, and in what states?
Ho w do you know?
- Sometimes the images can be processed by computer software. One of many possible enhancements of an image is
called stretching (increasing pixel contrast). You have probably seen stretched cloud images by a weather forecaster
on television. To illustrate the process of stretching, choose a colored pencil which has not been used in your color
code, such as blue or green. On one of your maps, color over all of the mid-level clouds with your blue or green pencil.
Using the graph you made yesterday, what temperatures correspond to the areas that you have stretched?
a. At the top of one of your outline maps, write the name of the satellite and its pass date - information
shown on the computer screen or provided by your teacher.
b. Work with your group members to determine the positions of low, medium, and high clouds on the image.
c. Use a color code and color in portions of your three maps as follows:
d. Repeat this process with each map and image.
dark color low level clouds, identify them by name on your map
gray mid level clouds, identify them by name on your map
red or yellow high level clouds, identify them by name on your map
