Cloud Types common cloud classifications Clouds are classified into a system that uses Latin words to describe the appearance of clouds as seen by an observer on the ground. The table below summarizes the four principal components of this classification system (Ahrens, 1994). LLaattiin RRoooott TTrraannssllaattiioonn EExxaammppllee fair weather cumulus cumulus heap stratus layer altostratus cirrus curl of hair cirrus nimbus rain cumulonimbus Further classification identifies clouds by height of cloud base. For example, cloud names containing the prefix "cirr-", as in cirrus clouds, are located at high levels while cloud names with the prefix "alto-", as in altostratus, are found at middle levels. This module introduces several cloud groups. The first three groups are identified based upon their height above the ground. The fourth group consists of vertically developed clouds, while the final group consists of a collection of miscellaneous cloud types. High-Level Clouds High-level clouds form above 20,000 feet (6,000 meters) and since the temperatures are so cold at such high elevations, these clouds are primarily composed of ice crystals. High-level clouds are typically thin and white in appearance, but can appear in a magnificent array of colors when the sun is low on the horizon. Photograph by: Knupp Mid-Level Clouds The bases of mid-level clouds typically appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Because of their lower altitudes, they are composed primarily of water droplets, however, they can also be composed of ice crystals when temperatures are cold enough. Photograph by: Holle Low-level Clouds Low clouds are of mostly composed of water droplets since their bases generally lie below 6,500 feet (2,000 meters). However, when temperatures are cold enough, these clouds may also contain ice particles and snow. Photograph by: Holle Vertically Developed Clouds Probably the most familiar of the classified clouds is the cumulus cloud. Generated most commonly through either thermal convection or or frontal lifting, these clouds can grow to heights in excess of 39,000 feet (12,000 meters), releasing incredible amounts of energy through the condensation of water vapor within the cloud itself. Photograph by: Holle Other Cloud Types Finally, we will introduce a collection of miscellaneous cloud types which do not fit into the previous four groups. Classifications High-Level Clouds Last Update: 07/09/97 Cloud types include: cirrus and cirrostratus.. Mid-Level Clouds Cloud types include: altocumulus,, altostratus. Low-Level Clouds Cloud types include: nimbostratus and stratocumulus.. Clouds with Vertical Development Cloud types include: fair weather cumulus and cumulonimbus.. Other Cloud Types Cloud types include: contrails,, billow clouds,, mammatus,, orographic and pileus clouds.. Cloud Classification The classification of clouds was first conceptualized by French naturalist Jean Lamarck in 1801. Two years later, in 1803, the English scientist Luke Howard created a classification which was later adopted by the International Meteorological Commission in 1929. The first scientific study of clouds began in 1803, when a method of cloud classification was devised by the British meteorologist Luke Howard. The next development was the publication in 1887 of a classification system that later formed the basis for the noted International Cloud Atlas (1896). This atlas, considerably revised and modified through the years (most recently in 1956), is now used throughout the world. Cloud types Clouds are generally classified according to genera in which Latin words are used to describe the appearance of clouds as seen by an observer on the ground. The table below summarizes the four principal components of this classification system. Latin Root ccuummuulluuss ssttrraattuuss cciirrrruuss nniimmbbuuss Translation hheeaapp llaayyeerr ccuurrl oof hhaaiirr rraaiinn Cloud altitude Clouds are further categorized according to their height above the ground (etages). These are: •• High-Level Clouds Forms above 20,000 feet (6,000 meters) and are primarily composed of ice crystals. Denoted by the prefix cirro- or or cirrus and includes cirrus, cirrocumulus, and cirrostratus. •• Mid-Level Clouds Their bases appear between 6,500 to 20,000 feet (2,000 to 6,000 meters). Composed primarily of water droplets although they can also be composed of ice crystals when temperatures are cold enough. Denoted by the prefix alto- and includes altostratus, altocumulus and nimbostratus. •• Low-level Clouds Their bases generally lie below 6,500 feet (2,000 meters). Mostly composed of water droplets but may also contain ice particles and snow. Includes stratus, stratocumulus, cumulus and cumulonimbus. When cloud particles become too heavy to remain suspended in the air, they fall to the earth as precipitation. Precipitation occurs in a variety of forms; hail, rain, freezing rain, sleet or snow. This portion of the Clouds and Precipitation module focuses on precipitation and has been organized into the following sections. Sections Rain and Hail Latest Update: 07/21/97 Atmospheric conditions that lead to the development of rain and hail. Freezing Rain A detailed look at freezing rain, associated dangers and the conditions that lead to its development. Sleet Atmospheric conditions that lead to the development of sleet. Snow Atmospheric conditions that lead to the development of snow. Acknowledgments Those who contributed to the Precipitation sections of the Clouds and Precipitation module. The navigation menu (left) for this section is called "Precipitation" and the menu items are arranged in a recommended sequence, beginning with this introduction. In addition, this entire web server is accessible in both "graphics" and "text"-based modes, a feature controlled from the blue "User Interface" menu (located beneath the black navigation menus). More information about the user interface options, the navigation system,, or WW2010 in general is accessible from About This Server .. InIn meteorology,, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena) is any product of the condensation of atmospheric water vapor that is pulled down by gravity and deposited on the Earth's surface.[1] The main forms of precipitation include rain,, snow,, ice pellets,, and graupel. It occurs when the atmosphere, a large gaseous solution, becomes saturated with water vapour and the water condenses, falling out of solution (i.e., precipitates).).[2] Two processes, possibly acting together, can lead to air becoming saturated: cooling the air or adding water vapour to the air. Virga is precipitation that begins falling to the earth but evaporates before reaching the surface; it is one of the ways air can become saturated. Precipitation forms via collision with other rain drops or ice crystals within a cloud.. Moisture overriding associated with weather fronts is an overall major method of precipitation production. If enough moisture and upward motion is present, precipitation falls from convective clouds such as cumulonimbus and can organize into narrow rainbands.. Where relatively warm water bodies are present, for example due to water evaporation from lakes, lake-effect snowfall becomes a concern downwind of the warm lakes within the cold cyclonic flow around the backside of extratropical cyclones. Lake-effect snowfall can be locally heavy. Thundersnow isis possible within a cyclone's comma head and within lake effect precipitation bands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized within windward sides of the terrain at elevation. On the leeward side of mountains, desert climates can exist due to the dry air caused by compressional heating. The movement of themonsoon trough,, or or intertropical convergence zone, brings rainy seasons toto savannah climes.. Rain drops range in size from oblate, pancake-like shapes for larger drops, to small spheres for smaller drops. Precipitation that reaches the surface of the earth can occur in many different forms, including rain,, freezing rain,, drizzle,, ice needles,, snow,, ice pellets or sleet, graupel and hail. Hail is formed within cumulonimbus clouds when strong updrafts of air cause the stones to cycle back and forth through the cloud, causing the hailstone to form in layers until it becomes heavy enough to fall from the cloud. Unlike raindrops, snowflakes grow in a variety of different shapes and patterns, determined by the temperature and humidity characteristics of the air the snowflake moves through on its way to the ground. While snow and ice pellets require temperatures close to the ground to be near or below freezing, hail can occur during much warmer temperature regimes due to the process of its formation. Precipitation may occur on other celestial bodies, e.g. when it gets cold, Mars has precipitation which most likely takes the form of ice needles, rather than rain or snow.[3] The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. Global warming is also causing changes in the precipitation pattern globally, including wetter conditions across eastern North America and drier conditions in the tropics. Precipitation is a major component of the water cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 cubic kilometres (121,000 cu mi) of water falls as precipitation each year; 398,000 cubic kilometres (95,000 cu mi) of it over the oceans.[4]