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Everey thing you need to know

Scott Leadley

on 5 February 2013

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Transcript of clouds

Cloud Formations What make clouds form 3. Frontal - Clouds are formed when a mass of warm air rises up over a mass of cold, dense air over large areas along fronts. A 'front' is the boundary between warm, moist air and cooler, drier air. There are many forms of clouds, the most common clouds are the ones shown to the left of the screen. Clouds will either be composed of ice or water droplets depending on the height of the cloud and the temperature of the atmosphere. Clouds are made of tiny drops of water or ice crystals that settle on dust particles in the atmosphere.

The droplets are so small they are approximately hundredth of a millimeter in dynamiter 1. The amount of water in the air has increased - for example through evaporation - to the point that the air cannot hold any more water. Clouds will either be composed of ice or water droplets depending on the height of the cloud and the temperature of the atmosphere. Because the droplets are so small, they can remain in liquid form in temperatures as low as -30 °C.

Clouds are continually changing and appear in an infinite variety of forms. The classification of clouds is based on a book written by Luke Howard. a London pharmacist and amateur meteorologist, in 1803.His book, The Modifications of Clouds, named the various cloud structures he had studied. 1. Surface heating - This happens when the ground is heated by the sun which heats the air in contact with it causing it to rise. The rising columns are often called thermals. Surface heating tends to produce cumulus clouds. THE END We hope you enjoyed the presentation. Created by Scott & Cameron Cirrus These clouds are thin and wispy and generally occur in fair weather, forming at high level. However, changes in the cloud may indicate that there will be heavy rain within 2 days. watch out for them joining together, thickening or moving lower in the sky. If however the cloud is not moving it means it will stay dry for the next couple of days. Nimbostratus Altocumulus Altocumulus clouds appear as parallel bands or in rounded masses. They can be distinguished from high-level Airrocumulus by the fact that they are often shaded. If you wake up to a warm and humid morning although the sky is covered with Altocumulus clouds , watch out thunderstorms are likely to occur later in the day. Even if it`s not warm and humid, although Altocumulus clouds are still present, expect a hard and heavy rain or hail storm later in the day. hkj These high level clouds can cover the entire sky. Although they can be thousands feet thick,they are fairly transparent. You can identify the cirrustratus from halo that appears around the sun or the moon. If this halo begins to shrink, the cloud is thickening and precipitation is likely within the next 12 hours. Cirrostratus Cirrostratus Cirrus Altocumulus What forms condensation
2. The air is cooled to its point - the point where the condensation occurs - and the air is unable to hold any more water Height of base:
Shape: Other features: 17,000 ft to 35,000 ft Composed of ice crystals, therefore white. Delicate filaments, or denser, entangled white Upper cumulonimbus is also cirrus. Cirrus is the highest of the ten main clouds and are composed entirely of ice crystals, typically forming above 24,000 ft in temperate regions of the world. cirrus rarely appear very thick. they are often seen with the other high clouds, cirrostratus and cirrocumulus and like them they can show a halo of phenomena around the sun or moon. Up at the top of the troposphere, winds will often be going at a speed of 100-150mph, forming gales that are constantly blowing cirrus to a different place. Not only are cirrus the highest clouds they are also the fastest clouds, although they look like the slowest clouds because they are so far away. Different species of Cirrus Fibratus: When the cloud is in the form of straight or curved filaments that are mostly distinct from each other and do not terminate in hooks or clumps. Floccus: When the cloud is in a form of independent small round tufts, which often show trails of ice crystals falling from them. Spissatus: The thickest cirrus. When it is in patches that appear grey in front of the sun which tends to originate from the anvil of a cumulonimbus. 2. Topography or orographic forcing - The topography - or shape and features of the area - can cause clouds to be formed. When air is forced to rise over a barrier of mountains or hills it cools as it rises. Layered clouds are often produced this way. Nimbostratus This cloud you will find low in the sky, its dark shade blocking the suns rays. Nimbostratus will provided persistent precipitation. It can be distinguished from Altostratus by the fact that the sun or moon is not visible beyond the cloud. Height of base:
Other features: 1,500 ft to 10,000 ft. Dark grey A thick, defused layer covering most of the sky Sun or moon not visible. Means rain or snow Nimbostratus are thick grey featureless clouds that cause prolonged heavy rain, snow or ice pellets. Nimbostratus are the deepest of all the layered clouds sometimes extending from 2,000 ft up to around 18,000 ft and generally extend over many square miles. As with over precipitating clouds, the falling precipitation can cause Stratus fractus to form in the air below Nimbostratus clouds. these are known as pannus and appear as shreds of cloud looking darker than the underside of Nimbostratus. Different species of Nimbostratus There are no species because the clouds appearance is so uniform. Hieght of base:
other features: 1,200 ft to 6,500 ft. White flakes with a grey tinge. Smooth silky streaks. They are transparent Cirrostratus are transparent high clouds covering large areas of the sky. They sometimes produce white or coloured rings, spots or arcs of light around the sun or moon that are known as halo phenomena. Different species of Cirrostratus Fibratus: is when the cloud veil has a fine or striated appearance. Nebulosus: is when the cloud shows no variation in tone 2. The air is cooled to its dew point - the point where condensation occurs and the air is unable to hold any more water. Here is an example of condensation on the in side of a window Height of base:
Other features: 7,000 ft to 17,000 ft. The High Clouds Grey or white, generally with some shading. Either patches or sheet of rounded elements. May produce slight rain or snow. Altocumulus is a mid-level cloud usually appearing in a patch or layer of more or less regularly spaced out cloud clumps, which are often given the name cloudlets. the cloud forms about halfway between the ground and the top of the troposphere. Altocumulus can be in the shape of rounded clumps, rolls or almonds. these are white or grey. Altocumulus are usually composed of droplets, although they may also contain ice crystals Different species of Altocumulus Stratiformis: Most common, when the cloudlets extend over large area. Castellanus: when the cloudlets have crennalled tops. Lenticularis: when the cloud is in the form of one or more individual almonds or lens shaped masses that appear dense, with pronounced shading. Altostratus This medium level cloud type can be distinguished from the Cirrostratus by the contrasting lack of halo around the sun or moon. Looking at the sun or moon through this cloud is like looking through frosted glass. Watch out for the cloud darkening in colour, as this can suggest that rain will occur within two days. Altostratus Height of base:
Other features: 8,000 ft to 17,000 A sheet totally or partly covering the sky. Objects on ground do not cast shadows. Grey and blue with tinge. Altostratus are mid level layers of grey cloud, which are either featureless or fibrous in appearance and typically extend over an area of several thousand square miles. They are usually composed of both water droplets and ice crystals thay are often thin enough in parts to reveal the position of the sun, which through like ground glass. Altostratus can cause a white or coloured corona around the sun or moon. The Clouds in the middle Different species of Altostratus There are no species as the cloud is so uniform Cumulus Cumulus Appearing in the sky for 5 or 40 minutes, these clouds look like floating cotton and are distinctive for there flat bases and noticeable outlines. Expanses of clear sky often appear between them. Usually appearing in fair weather, be warned that sometimes these clouds can grow into towering Cumulonimbus clouds suggesting heavy rain or thunderstorms. height of base:
Other features: 1,000 ft to 1,200 ft. White with dark undersides. Detached heaps in a shape of a cauliflower May produce small rain fall Cumulus are low detached puffy clouds that develop vertically in rising mounds, domes or towers and have generally flat bases. there upper parts often resemble cauliflowers and they appear brilliant white when reflecting high sunlight, although they can look dark when the sun is behind them. Different species of Cumulus Fractus: Raged edges and broken up. Can form in the moist air below rain clouds. Congestus: Maximum vertical extend. The tops are like cauliflower. Appear taller than they are wide because of brief downpours. Humulis: Minimal vertical extend. They look fattened and appear wider than they are tall. They do not cause precipitation. Cumulonimbus Cumulonimbus These clouds are larger and more vertically developed than the Cumulus cloud. These clouds typically develop in the afternoon or evening when the effects of the suns heat are most powerful. they may develop into individual towers, or develop as a line of towers Height of base:
Other features: 1,000 ft to 5,000 ft. White with dark threatening undersides. A tall Cumulus type cloud. Accompanied by heavy rain. Cumulonimbus are thunderstorm clouds characterised by their enormous height. They are typically tall enough to reach the top of the troposphere. Where they spread out in plumes of ice particals that can appear smooth fibrous or striated. They have dark bases and produce heavy showers and often hail which can be accompanied by thunder and lightning. Different species of Cumulonimbus Calvus: When the upper region is of soft indistinct flattened mounds with out any fibrous or striated appearance. Capillatus: When the upper region is like Cirrus and fibrous or striated, often in the shape of an anvil, plume or a disorderly mass of white hair. Stratus Stratus clouds are very low level grey layers or patches of clouds with fuzzy edges. They are the lowest clouds and sometimes appear at ground level in the form of mist or fog. Stratus clouds are a fairly uniform grey or white colour and may be accompanied by drizzle, snow or snow grains. If there are no other clouds above the layer of Stratus cloud, the sun or moon may shine through. Stratus Height of base:
Other features: Usually grey. Surface to 1,500 ft. May appear with a fairly uniform base. If thin, sun or moon will be visible. Stratus are grey layers or patches of cloud with very diffused edges. they are the lowest forming of all the cloud genera, sometimes appearing at ground level, thats when they are called fog or mist. Different species of Stratus Nebulusos: By far the most common, when it is in a grey and generally featureless layer. Fractus: When it is in a separate, raged shreds of grey cloud. this can appear in the region below precipitating clouds, when it is called pannus.though not particularly thick, these shreds can look quite dark against the base of the cloud above Stratocumulus Stratocumulus clouds appear in low lumpy layers.They are rounded in a shape with breaks of sky in between. You can find differentiate between the Stratocumulus and the Altocumulus by extending your arm towards the sky.
Look at the size of the clouds elements if they are approximately the size of your thumbnail it's a Altocumulus cloud. Stratocumulus If they are about the size of your fist it's a Stratocumulus cloud. Dark grey to light grey in colour, look out for these clouds beginning to merge. If they start to look like a Stratus cloud it's a sign of constant rain for the next twelve hours. Height of base:
Other features: 1,200 ft to 7,000 ft. Grey or white generally with shading. Patches or a sheet of rounded elements. May produce light rain or snow.
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