Clouds
Jessica Pixley
Weather and Climate
Robert Morris University

Clouds are an astonishing part of nature and help give us an idea of the current state of the weather. Clouds can vary dramatically in shape, size, color and position. Early in the nineteenth century French naturalist Jean-Baptitse Lamarck had started the first system to classify clouds which was polished by a naturalist named Luke Howard shortly after. Not until 1887 was Howards system finalized by Ralph Abercromby and Hugo Hildebrandson into the system we use today. This system entails four major cloud groups and ten basic types of clouds based on their appearance and position in the sky. The four groups are high clouds, middle clouds, low clouds, and clouds with vertical development.
The first cloud in the high cloud group is the Cirrus cloud. Cirrus clouds are formed by the freezing of water droplets. They can be found normally above twenty thousand feet. These clouds generally appear white or light grey in color. Strong western winds blow these clouds into thin wispy strands known as “mares’ tails”. In my opinion, these clouds look like they are painted into the sky. When cirrus clouds are present expect a nice pleasant day ahead.
The cirrocumulus is next in the high cloud group. These clouds generally are seen less than the cirrus cloud. These clouds are formed by ice crystals as well. They are also found above twenty thousand feet. If you hold you hand out and up at the sky these clouds will be about the size of the tip your pinky finger. They can also appear in rows which makes them easy to distinguish from the cirrus cloud. If these clouds cover the whole sky it is know as a “mackerel sky.” A mackerel is a type of fish and when the cirrocumulus clouds cover the whole sky it looks like a bunch of mackerel fish scales. When you see these clouds it is usually a fair, but cold day.
Last in the high clouds is the cirrostratus cloud. These clouds are the thinnest of the high clouds and are also made of ice crystals. If the sun or moon shines through these clouds it creates a “halo” around them. Sometimes this halo is the only indicator that the cloud is even there. If middle type clouds follow the cirrostratus clouds it usually indicates that precipitation will be occurring in the next day. The cirrostratus can also form before mid-latitude cyclone storm, yikes!
The next group of clouds is the middle clouds. Clouds in the middle group occur between sixty five hundred and twenty three thousand feet. If middle clouds form to be thick enough they can precipitate. The first cloud in this group is the altocumulus. The altocumulus can appear as round and puffy or more band like. These clouds appear to be grayish white and generally one part of the cloud is darker than the others. The presence of these clouds on a humid warm day usually is a warning for thunderstorms.
Next is the altostratus. These clouds are easily distinguished from the altocumulus because they appear more blueish gray in color, they are typically higher and the sum is dimly visible. Altostratus clouds usually cover the whole sky and appear before cyclonic storms having steady and ubiquitous precipitation.
Low clouds are the next group of clouds. Low clouds have bases lying below sixty five hundred feet. The nimbostratus cloud is the first in this group. The nimbostratus clouds are dark low level clouds that usually generate light to moderate, continuous precipitation. These clouds drift quickly with the wind and appear in a sheet like fashion. The sun and moon is not visible through these types of clouds.
The stratocumulus are next in the low level clouds. These clouds tend to be low and lumpy which are larger than the altocumulus. Stratocumulus clouds can appear light to dark gray and the sun is usually visible through the spaces between these clouds. These clouds can mean a light drizzle or flurries and, if you hold your arm out to the sky they are typically the size of a fist.
Last in the low clouds is the stratus which is the typically gray cloud that covers the whole sky. These clouds can make for a gloomy day and possibly some precipitation. These clouds can be mistaken for fog but they can be distinguished because they do not touch the ground as fog does.
The last of the four groups is clouds with vertical development. The first in this groups is the cumulus cloud. In my opinion this is the picture perfect cloud. These clouds look like pillow stuffing floating in the sky. These picture perfect clouds are usually the ”fair weather cumulus” which usually calls for fair weather. They can take many different shapes and sizes but usually appears white to light gray in color. These clouds can grow in size and become vertically developed and potentially turn into cummulus congetus or towering cumulus. Cummulus congestus are bascially a bunch of cummulus clouds merged together to form a line with a taller top. These clouds usually mean the rain is coming. If these clouds continue to develop vertically the become the cumulonimbus which is next in the the group. Cumulonimbus is a giant thunderstorm cloud. These clouds can develop up and down drafts that can become violent. The cumulonibus can sometimes reach up to tropopause and produce dangerous storms. These clouds can produce anything from rain to hail and can sometimes even develop into tornados. There are a few other clouds that are not generally seen and fall outside of the ten groups named above. There is a new cloud that has yet to be accepted by the WMO, and if it is accepted in will be the newest cloud since 1951. This just shows that meteorology continues to expand and continues to add to its exploration and studies.

References
Ahrens, D. (2015). Humidiy, Condensation, and CLouds. In Essentials of Meteorology (7th ed., pp. 105-114). Cengage Learning.

Cirrocumulus. (2012, January 1). Retrieved January 26, 2015, from http://www.windows2universe.org/earth/Atmosphere/clouds/cirrocumulus.html

Stratocumulus Clouds: Low, lumpy layer of clouds. (2010, January 1). Retrieved January 26, 2015, from http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/lw/strcu.rxml