What Would Make Air Cooler and Actually Rise Again

CLOUDS - HOW Do THEY FORM?

Air current is the horizontal movement of air, transporting energy transferred from the earth'due south surface as sensible and latent heat. Sensible rut is transferred past the processes of conduction and convection. Conduction transfers free energy within a substance, and convection transfers energy through the vertical movement of the heated substance. Latent oestrus is the transfer of energy by transforming the substance itself. As you recall, water has the ability to be as liquid, gas or solid. The transformation from liquid to gas is called evaporation; the reverse process, from gas to liquid, is called condensation; from liquid to solid is known as solidification (freezing); and from solid to liquid, fusion (melting). H2o tin besides be transformed directly from solid to gas (sublimation), or the reverse, through a procedure chosen degradation. We will encounter these various processes in the germination of clouds.

Clouds are formed when air contains as much water vapor (gas) as it can hold. This is called the saturation point, and it can be reached in 2 ways. Offset, wet accumulates until it reaches the maximum amount the volume of air tin can agree. The other method reduces the temperature of the moisture filled air, which in turn lowers the amount of wet it can contain. Saturation, therefore, is reached through evaporation and condensation, respectively. When saturation occurs, moisture becomes visible water aerosol in the form of fog and clouds.

It should exist noted that condensation past itself does not cause atmospheric precipitation (pelting, snowfall, sleet, hail). The moisture in clouds must become heavy enough to succumb to gravity and return to earth'southward surface. This occurs through two processes. In cold clouds ice crystals and water droplets be side past side. Due to an imbalance of water vapor pressure, the water droplets transfer to the ice crystals. The crystals eventually grow heavy plenty to fall to earth. In the second procedure, h2o droplets in warm clouds collide and change their electrical charge. Droplets of unlike charge attract 1 another and merge, thereby growing until they have sufficient weight to fall.

There is no divergence betwixt fog and clouds other than altitude. Fog is divers every bit a visible moisture that begins at a height lower than fifty anxiety. If the visible moisture begins at or above l feet, it is called a deject. Two mutual types of fog are chosen radiation fog and advection fog. Radiation fog forms during the night equally the earth's surface cools and the air immediately above it cools in turn past conduction. If the air is moist enough, the cooling causes it to reach saturation and visible water droplets form. We often call this blazon of fog ground fog because it lies so close to the surface. Advection fog forms when warm moist air moves over a colder surface (advection means to move horizontally). A perfect example is on the west coast of continents. Prevailing westerly winds motility moist air from over a warm ocean area to over the colder waters off the coast. Fog forms and is carried by the westerly over the land.

TOP

Although the formation of clouds and precipitation can be quite circuitous in full detail, nosotros tin can simplify the procedure into a simple recipe, good for the vast bulk of situations.

First, we need two basic ingredients: water and dust.

On Planet Earth, naturally occurring clouds are composed primarily of water in its liquid or solid state. (On other planets, clouds may form from other compounds such as the sulphuric acid clouds on Venus.) Thus, we brainstorm our recipe by collecting a sufficient quantity of h2o in the vapor state that we volition soon transform into the liquid or solid states. The h2o vapor content of the atmosphere varies from near zero to about 4 percent, depending on the wet on the surface below and the air temperature.

Next, nosotros need some grit. Non a large amount nor large particles and not all dusts will do. Without "dingy air" at that place would probable be no clouds at all or only high altitude ice clouds. Even the "cleanest" air institute on Earth contains most 1000 dust particles per cubic meter of air. Grit is needed for condensation nuclei, sites on which water vapor may condense or deposit as a liquid or solid. Certain types and shapes of dust and common salt particles, such every bit sea salts and clay, make the all-time condensation nuclei.

With proper quantities of h2o vapor and dust in an air parcel, the side by side step is for the air package mass to be cooled to a temperature at which cloud droplets or ice crystals can course. And, voila, we have clouds.

This simple recipe is a lot similar cooking craven -- you take a chicken and some spices, apply heat and later a time you have a cooked chicken. Merely just every bit there are many ways to cook craven, there are many unlike ways to course clouds.

THE Atmospheric precipitation LADDER
xi. Precipitation
10. DROPLET GROWTH
9. BUOYANCY/CLOUDINESS
8. CONDENSATION
7. SATURATION
six. HUMIDIFICATION
5. COOLING
4. EXPANSION
three. ASCENT
two. Muddy AIR
1. WATER VAPOR

Let us now expand our recipe and add precipitation. Professor John Mean solar day, the Deject Human being, has taken the simple cloud recipe, added a few more details and connected information technology until it also makes precipitation. He calls this The Precipitation Ladder. Every bit with our simple recipe, he begins the process with the basic ingredients of dirty air and water vapor. In Rungs 3 through 8, he takes the ingredients through several processes to grade a cloud.

Ascent and Expansion are two of the master processes that consequence in the cooling of an air parcel in which clouds will form. Nosotros mostly think of moving air as wind flowing horizontally beyond the surface. But air moving vertically is extremely important in weather processes, particularly with respect to clouds and atmospheric precipitation. Ascending air currents take united states up the Precipitation Ladder. (Where descending currents are present, we come down the Ladder with processes reversing until we are finally left with water vapor and grit in an air mass.)

There are four main processes occurring at or near the earth'southward surface which give can rise to ascending air: convergence, convection, frontal lifting and physical lifting.

Convergence occurs when several surface air currents in the horizontal period move toward each other to run into in a mutual space. When they converge, there is only one fashion to go: Up. A surface low pressure cell is an case of an expanse of convergence and air at its centre must rise as a result.

Convection occurs when air is heated from beneath past sunlight or past contact with a warmer land or h2o surface until it becomes less dense than the air above it. The heated package of air will ascent until it has once again cooled to the temperature of the surrounding air.

Frontal lifting occurs when a warmer air mass meets a colder 1. Since warm air is less dumbo than cold, a warm air mass budgeted a common cold 1 will ascend over the cold air. This forms a warm front end. When a cold air mass approaches a warm one, information technology wedges under the warmer air, lifting information technology above the ground. This forms a common cold front end. In either case, in that location is ascending air at the frontal boundary.

Physical lifting, as well known as orographic lifting, occurs when horizontal winds are forced to rise in social club to cross topographical barriers such as hills and mountains.

Whatever the process causing an air parcel to arise, the result is that the rising air parcel must change its pressure to be in equilibrium with the surrounding air. Since atmospheric pressure decreases with altitude, so too must the pressure level of the ascending air packet. Every bit air ascends, it expands. And as information technology expands, information technology cools. And the higher the parcel rises, the libation it becomes.

At present that we have begun cooling the air packet, nosotros are nigh set up to form a cloud. We must continue to cool the parcel until condensation is reached. The adjacent several rungs of the Precipitation Ladder describe the processes through to the condensation of liquid water.

As the air cools, its relative humidity will increase - a process Day terms humidification (Rung 6). Although nothing has yet happened to modify the water vapor content of the air, the saturation threshold of the air bundle has decreased every bit the air cooled. By decreasing the saturation threshold, the relative humidity increases. Cooling is the most important method for increasing the relative humidity but it is non the only one. Another is to add more than h2o vapor through evaporation or mixing with a more humid air mass.

If nosotros are to form a cloud, humidification may eventually bring the air inside the parcel to saturation. At saturation the relative humidity is 100 percentage. Unremarkably a little more than humidification is required which brings the relative humidity to over 100 percent, a state known equally supersaturation, before a cloud volition class. When air becomes supersaturated, its water vapor looks for ways to condense out. If the quantity and limerick of the dust content is ideal, condensation may brainstorm at a relative humidity beneath 100 percent. If the air is very clean, it may have loftier levels of supersaturation to produce cloud droplets. But typically condensation begins at relative humidity a few tenths of a percentage above saturation.

Condensation of water onto condensation nuclei (or degradation of water vapor equally ice on freezing nuclei) begins at a particular altitude known as the cloud base or lifting condensation level. Water molecules attach to the particles and form cloud aerosol which have a radius of about xx micrometers (0.02 mm) or less. The droplet volume is more often than not a million times greater than the typical condensation nuclei.

Clouds are composed of large numbers of cloud droplets, or ice crystals, or both. Because of their small size and relatively high air resistance, they can remain suspended in the air for a long time, particularly if they remain in ascending air currents. The boilerplate cloud droplet has a terminal autumn velocity of 1.three cm per 2nd in even so air. To put this into perspective, the average deject droplet falling from a typical low deject base of 500 meters/1,650 feet would take more than 10 hours to accomplish the ground.

We at present know that cirrus clouds in their various forms are composed of ice crystals, and the upper levels of tall cumulus may also have ice in them even in the summertime.

While clouds in their varied forms and appearances (See Deject Atlas) are a source of much interest, we volition leave them now and go along up the Atmospheric precipitation Ladder toward the top rung: Precipitation. Forming Precipitation Light Pelting

We know that not all clouds produce rain that strikes the ground. Some may produce rain or snow that evaporates earlier reaching the basis, and most clouds produce no atmospheric precipitation at all. When pelting falls, we know from measurements that the drops are larger than 1 millimeter. A raindrop of diameter 2 mm contains the h2o equivalent of a 1000000 deject aerosol (0.02 mm diameter). So if we are to get some atmospheric precipitation from a cloud, there must be additional process within the cloud to class raindrops from cloud droplets.

The next rung of the Atmospheric precipitation Ladder is Buoyancy or Cloudiness which signifies that we must increase the deject h2o content earlier nosotros can expect any precipitation.

This requires a continuation of the lifting process. Information technology is assisted past the holding of h2o of giving off rut when changing from vapor to liquid and solid states, the latent heats of condensation and of deposition, respectively. (If the vapor first changes to a liquid before freezing, then nosotros also take the latent heat of condensation released and followed by the release of the latent oestrus of freezing.) This additional rut release warms the air parcel. In doing so, the buoyancy of the packet relative to the surrounding air increases, and this contributes to the bundle's further rise. We can see the continued rising of these parcels in cumulus clouds that accomplish great vertical growth.

Now in the deject, there must be Growth of cloud droplets to sizes that can fall to the ground as rain (we will await at snowfall in a minute) without evaporating. Cloud aerosol can abound to a larger size in three ways.

The first is by the continued condensation of water vapor into cloud droplets and thus increasing their volume/ size until they become droplets. While the outset condensation of h2o onto condensation nuclei to class cloud aerosol occurs rather chop-chop, continued growth of cloud droplets in this manner will proceed very slowly.

2nd, growth by collision and coalescence of deject aerosol (so the collision of rain drops with cloud droplets and other drops) is a much quicker process. Turbulent currents in the clouds provide the first collisions between droplets. The combination forms a larger drop which can further collide with other aerosol, thus growing speedily in size.

As the drops grow, their autumn velocity also increases, and thus they can collide with slower falling aerosol. A 0.five mm-radius drop falling at a charge per unit of 4 g/due south can quickly overtake a 0.05 mm (50 micrometer) drop falling at 0.27 m/s. When drops are besides big, however, their collection efficiency for the smallest drops and droplets is not as not bad every bit when the drops are nearer in size. Small droplets may bounce off or flow effectually much larger drops and therefore do not coalesce. A drop about 60% smaller in diameter is most probable to be collected by a large drop.

Clouds with potent updraft areas take the best drop growth because the drops and aerosol stay in the deject longer and thus have many more collision opportunities.

Finally, it may seem odd, merely the best conditions for drop growth occur when ice crystals are present in a cloud. When in small droplet form, liquid water must be cooled well below 0 ° C (32 °F) before freezing. In fact, under optimal conditions, a pure droplet may reach -xl °C before freezing. Therefore, there are areas inside a cloud were ice crystals and water droplets co-exist.

When ice crystals and supercooled droplets are well-nigh each other, there is a movement of water molecules from the droplet to the crystal. This increases the size of the ice crystal at the expense of the droplet. When the crystals grow at temperatures around -ten °C (14 °F), they brainstorm to develop arms and branches, the stereotypical snow crystal. Such crystals non only are efficient at growing at the expense of water droplets, they also easily stick to one another forming big aggregates we call snowflakes.

Finally, the drops have grown to a size that they tin can autumn in a reasonable fourth dimension to the surface without evaporating, and we have reached the elevation rung Atmospheric precipitation. (For more on raindrops, click here.)The post-obit table gives some typical drop diameters for various rain types, using cloud droplets equally a reference size. Most rain falls in the range of 0.2 to 5 mm (0.008 to 0.20 inch).

Of course, not all precipitation falls as pelting. A fair amount of the world'due south atmospheric precipitation falls as snow or some other solid h2o form. Actually, exterior the tropical regions, it is likely that the much of the atmospheric precipitation begins in the solid form and only becomes liquid rain when information technology melts while falling through air with temperatures above freezing.

Most people telephone call almost any frozen course of precipitation, other than hail or ice pellets, a snowflake. But meteorologists are a bit more fussy. Technically the term snowflake refers to an aggregation of individual snow crystals that have bumped together and remain joined during their fall. Snowflakes typically fall when air temperatures near the world'southward surface are not far from the freezing mark. Snow crystals attach to each other better at these temperatures. At very common cold temperatures, snowflakes are uncommon and we encounter mostly snow crystals during a snow fall.

Snow crystals are typically 0.5 to 5 millimeters ( 0.02 to 0.20 inches) in size whereas snowflakes are about 10 mm in size (0.4 inches) and may be equally large every bit 200 to 400 mm (0.79 to one.57 inches).

Other common forms of solid precipitation are: hail, sleet or ice pellets, graupel or soft hail or snow grains, and a special grade: freezing pelting, likewise known as coat or rime. The latter falls as a liquid merely freezes on contact with an object. When articulate ice forms, freezing pelting is called glaze. When the water ice is milky, information technology is called rime.

Hail is a phenomenon of severe thunderstorms, requiring strong updrafts to form hailstones by passing the hailstone seed many times through air laden with drops and ice crystals.

Elevation

OUTLINE - CAUSES OF CLOUDINESS

1) Formation over area
A) Cooling of air to dew point
one) Lifting
a) Convection
1) Heating from below
A) Advection over warmer surface
B) Insolation
C) Advection of warm air in the lowest layers
ii) Cooling from above
A) Radiations from top of deject deck
B) Advection of cold air aloft
b) Mechanical lifting along a surface
1) Orographic
two) Overrunning along a potential temperature surface
3) Upglide along a frontal surface
c) Convergence
1) Depression pressure center of trough
2) Air current shear (speed and/or directional convergence)
3) Latitudinal alter (northward moving current)
4) Vorticity increment (due south moving electric current)
ii) Radiation (fog)
iii) Conduction from cooler surface (fog)
4) Mixing with cooler air mass
B) Increase in wet (warming dew bespeak to temperature)
1) Mixing
a) Caused past convection
b) Acquired by strong winds
2) Contact with moist surface
3) Evaporation from falling precipitation
ii) Advection from elsewhere
A) Formation in other expanse covered above
B) Changes during advection equally indicated to a higher place for the various operating processes

TOP

What causes clouds?
What influences the colour of clouds?
Why practise clouds stop growing upwards?
Why are there no clouds on some days?
Types of clouds
Depression clouds
Medium clouds
High clouds
Measuring clouds
The formation of precipitation

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What causes clouds?

A deject is defined as 'a visible aggregate of minute aerosol of water or particles of ice or a mixture of both floating in the gratis air'. Each droplet has a bore of about a hundredth of a millimeter and each cubic meter of air volition contain 100 million aerosol. Considering the aerosol are and then small, they tin remain in liquid form in temperatures of -xxx °C. If so, they are chosen supercooled droplets.

Clouds at college and extremely cold levels in the atmosphere are equanimous of ice crystals - these can be nigh a tenth of a millimeter long.

Clouds form when the invisible water vapor in the air condenses into visible h2o aerosol or water ice crystals. For this to happen, the package of air must be saturated, i.due east. unable to concur all the water information technology contains in vapor form, so information technology starts to condense into a liquid or solid form. In that location are 2 means past which saturation is reached.

(a) By increasing the water content in the air, east.g. through evaporation, to a point where the air tin can hold no more than.

(b) Past cooling the air so that information technology reaches its dew point - this is the temperature at which condensation occurs, and is unable to 'hold' whatsoever more water. Effigy 1 shows how there is a maximum amount of water vapor the air, at a given temperature, can hold. In full general, the warmer the air, the more water vapor it tin can concur. Therefore, reducing its temperature decreases its ability to concur water vapor and so that condensation occurs.

Method (b) is the usual way that clouds are produced, and it is associated with air rising in the lower office of the atmosphere. Every bit the air rises information technology expands due to lower atmospheric pressure, and the free energy used in expansion causes the air to cool. Generally speaking, for each 100 meters/330 anxiety which the air rises, it will absurd by 1 °C, as shown in Figure 2 . The charge per unit of cooling will vary depending on the h2o content, or humidity, of the air. Moist parcels of air may cool more than slowly, at a rate of 0.5 ° C per 100 meters/330 feet.

Therefore, the vertical rising of air will reduce its ability to concord water vapor, then that condensation occurs. The peak at which dew indicate is reached and clouds course is called the condensation level.

There are five factors which tin pb to air rising and cooling:

1. Surface heating. The ground is heated past the sun which heats the air in contact with it causing it to rise. The rising columns are often called thermals.
2. Topography. Air forced to rise over a bulwark of mountains or hills. This is known as orographic uplift.
3. Frontal. A mass of warm air rising up over a mass of cold, dense air. The boundary is called a 'front'.
iv. Convergence. Streams of air flowing from different directions are forced to rise where they run into.
5. Turbulence. A sudden alter in wind speed with summit creating turbulent eddies in the air.

Some other important factor to consider is that h2o vapor needs something to condense onto. Floating in the air are millions of infinitesimal common salt, dust and fume particles known as condensation nuclei which enable condensation to accept identify when the air is just saturated.

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What influences the color of clouds?

Low-cal from both the sky and from clouds is sunlight which has been scattered. In the case of the sky, the molecules of air (nitrogen and oxygen) undertake the handful, merely the molecules are so small that the blue part of the spectrum is scattered more than strongly than other colors.

The water droplets in the cloud are much larger, and these larger particles scatter all of the colors of the spectrum by near the same corporeality, so white low-cal from the sunday emerges from the clouds still white.

Sometimes, clouds accept a yellowish or brownish tinge - this is a sign of air pollution.

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Why do clouds stop growing upwards?

Condensation involves the release of latent heat. This is the 'invisible' oestrus which a water droplet 'stores' when it changes from a liquid into a vapor. Its subsequent change of form again releases enough latent oestrus to make the damp packet of air warmer than the air surrounding it. This allows the parcel of air to rise until all of the 'surplus' water vapor has condensed and all the latent heat has been released.

Therefore, the main reason which stops clouds growing upwards is the end of the release of latent heat through the condensation procedure. In that location are two other factors which likewise play a role. Faster upper atmospheric winds can plane off the tops of tall clouds, whilst in very high clouds, the deject might cross the tropopause, and enter the stratosphere where temperatures rising, rather than decrease, with altitude. This thermal modify will prevent further condensation.

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Why are in that location no clouds on some days?

Even when information technology is very warm and sunny, there might not be any clouds and the sky is a clear blueish. The usual reason for the absence of clouds volition be the type of pressure, with the area existence nether the influence of a high pressure level or anticyclone. Air would be sinking slowly, rather than rising and cooling. As the air sinks into the lower part of the atmosphere, the force per unit area rises, information technology becomes compressed and warms up, then that no condensation takes place. In simple terms, there are no mechanisms for clouds to class under these pressure conditions.

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Types of clouds

In 1803 a retail chemist and amateur meteorologist called Luke Howard proposed a system which has subsequently get the basis of the present international classification. Howard also become known by some people as "the male parent of British meteorology", and his pioneering work stemmed from his marvel into the vivid sunsets in the belatedly 18th century following a serial of violent volcanic eruptions. They had ejected dust loftier upwards into the atmosphere, thereby increasing the amount of condensation nuclei, and producing spectacular cloud formations and sunsets.

Howard recognised four types of deject and gave them the following Latin names:

Cumulus - heaped or in a pile
Stratus - in a sheet or layer
Cirrus - thread-like, hairy or curled
Nimbus - a rain bearer

If nosotros include another Latin word altum meaning pinnacle, the names of the x main cloud types are all derived from these five words and based upon their advent from basis level and visual characteristics.

The cloud types are split into iii groups co-ordinate to the height of their base above mean sea level. Note that 'medium' level clouds are prefixed by the discussion alto and 'high' clouds by the discussion cirro (see Table one). All heights given are approximate above sea level in mid-latitudes. If observing from a hill superlative or mountain site, the range of bases will accordingly be lower.

Low clouds Surface - vii,000 ft
Medium clouds 7,000 - 17,000 ft
High clouds 17,000 - 35,000 ft

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LOW CLOUDS

Cumulus (Cu)
Peak of base: 1,200-6,000 ft
Colour: White on its sunlit parts merely with darker undersides.
Shape: This cloud appears in the form of detached heaps. Shallow cumulus may appear quite ragged, peculiarly in potent winds, but well formed clouds take flattened bases and sharp outlines. Large cumulus clouds have a distinctive "cauliflower" shape.
Other features: Well developed cumulus may produce showers.

Cumulonimbus (Cb)
Height of base of operations: 1,000-five,000 ft
Color: White upper parts with dark, threatening undersides.
Shape: A cumulus-blazon cloud of considerable vertical extent. When the acme of a cumulus reaches dandy heights, the water droplets are transformed into water ice crystals and it loses its articulate, precipitous outline. At this stage the cloud has become a cumulonimbus. Oft, the fibrous cloud top spreads out into a distinctive wedge or anvil shape.
Other features: Accompanied by heavy showers, perhaps with hail and thunder. By convention Cb is normally reported if hail or thunder occur, fifty-fifty if the observer does not immediately recognise the deject as Cb; (it may exist embedded inside layers of other deject types).

Stratus (St)
Pinnacle of base of operations: surface-1,500 ft
Color: Usually grey.
Shape: May announced equally a layer with a fairly uniform base of operations or in ragged patches, specially during precipitation falling from a cloud layer above. Fog will often lift into a layer of stratus due to an increment in current of air or ascension in temperature. As the sun heats the footing the base of operations of stratus cloud may ascension and intermission becoming shallow cumulus cloud equally its edges take on a more distinctive class.
Other features: If thin, the disc of the sunday or moon will be visible (providing there are no other deject layers above). If thick, information technology may produce drizzle or snow grains.

Stratocumulus (Sc)
Height of base: 1,200-vii,000 ft
Color: Grey or white, generally with shading.
Shape: Either patches or a canvass of rounded elements just may also appear equally an undulating layer. When viewed from the ground, the size of individual elements volition have an apparent width of more than 5degree when at an tiptop greater than 30degree (the width of 3 fingers at arm's length).
Other features: May produce light rain or snow. Sometimes the cloud may result from the spreading out of cumulus, giving a light shower.

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MEDIUM CLOUDS

Altocumulus (Ac)
Superlative of base of operations: 7,000-17,000 ft
Color: Gray or white, more often than not with some shading.
Shape: Several different types, the most common being either patches or a sheet of rounded elements but may besides appear as a layer without much grade. When viewed from the basis, the size of private elements will accept an apparent width of ane to 5degree when at an elevation greater than 30degree (the width of 1 to three fingers at arm's length). Fifty-fifty if the elements appear smaller than this the deject is still classified altocumulus if it shows shading.
Other features: Occasionally some slight rain or snow, possibly in the grade of a shower may achieve the ground. On rare occasions, a thunderstorm may occur from i type of Air conditioning known every bit altocumulus castellanus — so called because in outline, the cloud tops expect like a serial of turrets and towers along a castle wall.

Altostratus (As)
Meridian of base: 8,000-17,000 ft
Color: Greyish or bluish.
Shape: A canvas of uniform advent totally or partly covering the sky.
Other features: Sometimes thin enough to reveal the sun or moon vaguely, as through ground glass. Objects on the ground exercise not cast shadows. May give generally calorie-free rain or snowfall, occasionally ice pellets, if the cloud base is no higher than nigh 10,000 ft.

Nimbostratus (Ns)
Height of base: i,500-ten,000 ft
Colour: Dark grey.
Shape: A thick, diffuse layer covering all or most of the sky. Other features: Sun or moon always blotted out. Accompanied by moderate or heavy rain or snow, occasionally ice pellets. Although classed every bit a medium cloud, its base of operations oftentimes descends to low cloud levels. May exist partly or fifty-fifty totally obscured by stratus forming underneath in precipitation.

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High CLOUDS

Cirrus (Ci)
Height of base: 17,000-35,000 ft
Color: Composed of water ice crystals, therefore white.
Shape: Delicate hair-like filaments, sometimes hooked at the end; or in denser, entangled patches; or occasionally in parallel bands which appear to converge towards the horizon. Other features: The remains of the upper portion of a cumulonimbus is also classified as cirrus.

Cirrocumulus (Cc) Height of base: 17,000-35,000 ft
Color: Composed of ice crystals, therefore white.
Shape: Patches or sail of very pocket-size elements in the form of grains or ripples or a honeycomb. When viewed from the footing, the size of individual elements will have an apparent width of less than 1degree when at an elevation greater than 30degree (no greater than the width of a little finger at arm's length).
Other features: Sometimes its appearance in a regular pattern of 'waves' and minor gaps may resemble the scales of a fish, thus giving rise to the pop name 'mackerel sky'. (this name may as well exist attributed to loftier altocumulus clouds).

Cirrostratus (Cs) Superlative of base: 17,000-35,000 ft
Color: Composed of ice crystals, therefore white.
Shape: A transparent veil of gristly or polish appearance totally or partly covering the sky.
Other features: Thin plenty to allow the sun to cast shadows on the ground unless it is depression in the sky. Produces halo phenomena, the most frequent beingness the small (22degree ) halo around the sun or moon — a little more than the distance between the top of the thumb and the piddling finger spread broad apart at arm's length.

Condensation trails (contrails)
These are thin trails of condensation, formed by the water vapor rushing out from the engines of jet aircraft flying at loftier altitudes. They are not truthful clouds, but tin can remain in the sky for a long time, and abound into cirrus clouds.

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Measuring clouds

The cloud amount is defined as 'the proportion of the celestial dome which is covered past deject. The calibration used is eighths, or oktas, with observers standing in an open up space or on a rooftop to get a adept view or panorama of the heaven.

Complete deject cover is reported every bit 8 oktas, half cover as iv oktas, and a completely clear heaven as zero oktas. If in that location is low-lying mist or fog, the observer will report sky obscured.

The reporter volition also report the amount of each cloud level — two oktas of cumulus and 3 oktas of cirrus, etc.

The frequent passage of depressions beyond the Uk means that the most commonly reported cloud amount is, non surprisingly, 8 oktas. A clear blueish sky, i.due east. zero oktas, is less common, as often on hot, sunny days, in that location are small wispy layers of cirrostratus or fine tufts of thin cirrus at loftier altitudes.

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The germination of atmospheric precipitation

Cooling, condensation and deject formation is the start of the process which results in precipitation. Just non all clouds will produce raindrops or snowflakes — many are so short-lived and small that there are no opportunities for atmospheric precipitation mechanisms to starting time.

At that place are two theories that explain how minute cloud droplets develop into atmospheric precipitation.

1. The Bergeron-Findeisen ice-crystal mechanism

If parcels of air are uplifted to a sufficient height in the troposphere, the dew point temperature volition be very depression, and minute water ice crystals volition starting time to grade. The supercooled water aerosol will too freeze on contact with these ice nuclei.

The ice crystals after combine to form larger flakes which attract more supercooled aerosol. This process continues until the flakes fall back towards the footing. As they autumn through the warmer layers of air, the ice particles cook to form raindrops. However, some ice pellets or snowflakes might be carried downward to footing level by cold downdraughts.

2. Longmuir'southward standoff and coalescence theory

This applies to 'warm' clouds i.e. those without large numbers of water ice crystals. Instead they comprise water droplets of many differing sizes, which are swept upward at dissimilar velocities and so that they collide and combine with other droplets.

It is idea that when the droplets have a radius of 3 mm, their movement causes them to splinter and atomize, forming a fresh supply of h2o droplets.

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Man-made rain

In recent years, experiments have taken place, importantly in the U.s.a. and the former USSR, adding particles into clouds that human action equally condensation or freezing nuclei. This cloud seeding involves the add-on into the temper from aircraft of dry ice, silver iodide or other hygroscopic substances. These experiments take largely taken identify on the margins of farming areas where rainfall is needed for crop growth.

TOP

Clouds tin can form anywhere in the troposphere, and although condensed liquid, they are light plenty to bladder in the air and move from place to place by the wind. Clouds are classified according to appearance and tiptop. Based on appearance, at that place are two major types: Clouds of vertical development, formed by the condensation of rising air; and clouds that are layered, formed by condensation of air without vertical movement. When clouds are classified by superlative, there are four classes: high, center, depression, and vertical development.

Cloud names, of which at that place are twelve, combine advent and height. A cursory description of the root proper noun will betoken this combination of features.

Stratus, strato....Layered or sheetlike
Cumulus, cumulo....Puffy, heaped (vertical)
Nimbus, nimbo......Night and rainy
Cirrus, cirro......Curly, featherlike (high cloud)
Alto...............Loftier (but used to describe a center cloud)
Fracto.............Cleaved

Permit's describe a few familiar cloud formations. The opposite of fog, in terms of altitude, are cirrus clouds. These clouds develop at an average height of 20,000 anxiety. Cirrus clouds look like a person'south pilus, or feathers blowing in the wind. At this altitude, the air is so cold that the cloud is composed of ice crystals rather than water aerosol found at lower altitudes. The strong wind at this high distance accident the clouds in long streamers across the heaven.

Another cloud that is formed looks similar sheets across the sky. These are stratus clouds. Stratus clouds course when condensation happens at the same level at which the air stops rising. Nosotros notice this on days when the stratus clouds are spread across the heaven and it becomes overcast. The skies may take these stratus clouds for days and it too brings rain.

Cumulus clouds are the clouds that seem to make pictures in the sky. Ane can make many shapes and designs by watching the clouds pass by overhead. These clouds have a flat bottom and a billowy elevation. The base of the cloud forms at the altitude at which the rising air cools and condensation starts. However, ascent air remains warmer than the surrounding air and continues to ascension. As it rises, more vapor condenses, forming the billowing columns.

The remaining clouds accept been named by combining terms. For example, clouds that are sheet-similar yet accept vertical structure are called stratocumulus. The table beneath shows all 12 cloud names. While almost rain clouds are in the depression deject range, because most moisture is nearer to the earth's surface, special mention should be made of those clouds in the vertical development category. We mentioned before hurricanes and tornadoes earlier. These thunderstorms arise from cumulonimbus clouds, which can attain heights of 65,000 feet and builds through all the layers. When the cloud reaches the top of the troposphere it is virtually lopped off past the chapeau which the stratosphere creates, and the cumulonimbus deject resembles a giant anvil.

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Source: https://www.weather.gov/source/zhu/ZHU_Training_Page/clouds/cloud_development/clouds.htm

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