The lowest cloud height. How are clouds formed? Altostratus translucent clouds

Hello friends! Clouds, white-maned horses ... Oh, what am I talking about🙂Actually, I want to talk about how clouds form, where they form and what are the reasons for this, and what other types of clouds are ...

Masses of water vapor carried through the air are clouds. At any given time, about 50% of the earth's surface is covered by clouds. Clouds are also part of a process that provides fresh water all living things on .

When the vapor rises, it cools and again turns into a solid (ice) or liquid (water) state, forming clouds (invisible masses). In the form that is carried away by streams and rivers, moisture returns to Earth, and the cycle repeats.

How are clouds formed?

Clouds are made up of ice and/or water. Everywhere in there is water vapor, which evaporates from the oceans and seas. " Absolute humidity» air determines the amount of steam in given volume air. The higher the temperature, the more water vapor can be contained in the air.

If the air contains the maximum possible amount of water vapor for a given temperature, it is considered "saturated", and its " relative humidity» equals 100%. The "dew point" is the corresponding temperature. The process of changing water vapor into a solid or liquid state, which takes place when the air containing the vapor cools and becomes saturated, is called condensation.

Air cooling.

As a result of the rise, the air can cool, for example, when it flows over hills. At the same time, using part of its heat, it expands due to a pressure drop (“adiabatic expansion”). Clouds form when excess water vapor condenses into water droplets when the temperature drops to a certain point.

The main causes of air rise, which lead to its cooling, the formation of clouds and condensation: the first is caused by a sharp change in the speed and direction of the wind and creates everything the necessary conditions for cloud formation turbulence.

The second - when passing over the mountains and hills, the "spelling rise" of air. In this case, various types of clouds can form: a cloud cap, mountain fog, vortex, flag-like and lentil-shaped clouds.

When it cools down to the dew point wet air, before reaching the top, mountain fog appears. Everything is perceived as something that fell into such a cloud and clings to the top and windward side.

With rather dry air, which cools after rising above the top of the mountain to the dew point, a cloud cap forms. It seems that the cloud is hanging motionless over the top of the mountain, even despite the wind. This is not the same cloud, strictly speaking, it is constantly formed on the windward side and evaporates on the leeward side.

Pennant-like, flag-like clouds form over mountain peaks when air is forced to flow around the peak on both sides, creating turbulent lift sufficient to create clouds and eddies in the moist air currents on the lee side of the mountain.

The cloud that has formed behind the peak flows downwind and eventually evaporates. On the crests of undulating air currents that pass over rough terrain, lenticular undulating clouds often form.

A vortex cloud in the form of an elongated cylinder can form, located parallel to a mountain range on its leeward side in a turbulent vortex.

Convergence.

Inside huge weather systems - "cyclones" (areas low pressure), air masses can also rise.

When, "fighting" for free space, warm wet masses "converge" (converge) with cold air masses - large ridges of clouds form. Up displaces lighter and warmer air - denser and colder. Often such a "front" brings prolonged rains and heavy rainfall.

The nature of the upward movement of air masses determines the shape of the clouds. Slowly ascending air currents (5 - 10 cm/sec.) usually form stratus clouds, and warm air - cumulus clouds, which rise from the surface at least 100 times faster than stratus clouds.

Scientists have found that in these clouds, air currents can rise at speeds of up to 100 km/h, and how high they rise depends largely on the "instability" or "stability" of the air through which they pass.

The air in the cloud cools by 1°C for every 100 m of ascent. "Stable" conditions are when high speed the temperature of the surrounding air drops, while this flow continues to rise.

"Unstable Conditions" this is when the surrounding air cools more slowly, and the updrafts soon reach the same temperature and the rise stops.

Cloud classification.

Clouds, influenced by the many processes involved in their formation, are different shapes, colors and sizes. Ancient scientists, long before they began to understand the reasons for the formation of clouds, tried to classify and describe their diversity.

Jean Baptiste Lamarck (1744 - 1829), the French founder of the theory of evolution, as well as a naturalist, was one of the first among them.

He proposed to classify clouds into five types and three levels in 1802. Lamarck believed that clouds formed as a result of a series of circumstances (although he did not know exactly what), and not by chance.

The English chemist Luke Howard, in the same year 1802, developed a classification that included three main types of clouds, and also gave them Latin names: Stratus is stratiform, Cirrus is pinnate and Cumulus is cumulus.

And these basic terms are also used today. The first "international cloud atlas" was published in 1896. At that time, clouds were still considered to be non-developing, constant masses. But the fact that each cloud has its own life cycle became clear by the 1930s.

Today, the World Meteorological Organization (WMO) distinguishes 10 main types of clouds according to their shape and height. Each type has a common abbreviation.

Soaring above.

To upper clouds include cirrostratus (Cs), cirrocumulus (Cc) and cirrocumulus (Ci). They are composed of ice crystals, occur at altitudes of 6 to 18 km, and are not a source of precipitation that falls on Earth.

Cirrus clouds have the shape of individual thin white hairs. Wavy plates or white patches resemble cirrocumulus clouds. And on the transparent veil thrown to the sky, cirrostratus clouds look like.

Middle clouds - Altostratus (As) and Altocumulus (Ac) - consist of a mixture of ice crystals and water droplets, and are located at an altitude of 3 - 6 km. Altocumulus clouds look like white-gray broken plates, and altostratus clouds look like gray-blue whole sheets. Very little precipitation falls from mid-tier clouds.

Lower clouds (up to 3 km high) include Stratocumulus (Cs), Cumulus (Cu), Stratocumulus (Ns), Stratus (St), and Cumulonimbus (Cb). Cumulus, stratocumulus and stratus are made up of droplets, while stratonimbus and cumulonimbus are made up of a mixture of ice and water.

Stratus and stratocumulus clouds look like a gray canvas, but the former are a homogeneous layer, while the latter are more fragmented. They may come in drizzle or light rain. Nimbostratus clouds look like a dark gray layer, they carry snow or heavy rains.

Vertically rising cumulus clouds have clear outlines and a dense structure. They may be accompanied by showers. Cumulonimbus are dark, large and dense clouds (sometimes with an anvil-flat top) associated with thunderstorms and heavy rain.

Now, looking at the sky, you can understand what kind of clouds are there and what weather should be expected...

The question "What is a cloud?" people asked back in those distant times when only the birds and the clouds themselves flew across the sky. Wikipedia did not yet exist then, and no one had yet invented or published the Children's Encyclopedia. Therefore, some dreamers just didn’t come up with to explain this phenomenon of nature.

Because clouds look so soft and fluffy from below, there was a time when people thought they were made of fluff.

There were also more amusing assumptions about what these heavenly formations are made of. They even said that building material white hulks floating across the sky is cotton candy.

Of course, these are inventions. What the cloud consists of, scientists learned at the end of the 18th century. It happened when mankind found a way to rise into the sky. It was then that it was possible to answer the question: what does the cloud consist of? It turned out that the clouds that seem white and dense from below are actually ordinary fog. So walking in foggy weather is like traveling through a cloud.
In those same years, people learned what clouds are made of. After all, before that, their nature was also explained in different ways. But all this will be discussed a little later.

In general, clouds can consist not only of water droplets, like ordinary fog, but also of ice crystals. It all depends on how high they are.

Most often, clouds appear at an altitude of 6 to 20 km from the surface of our planet. This part of the atmosphere is called the troposphere. It is here that clouds are formed, consisting of water droplets. The temperature inside such formations is usually above -10 0 C. The clouds that form at this height can have a different structure and shape.

There are also clouds that are born much higher. For example, the so-called mother-of-pearl clouds are born 20-25 km from the Earth. However, the champions are almost invisible noctilucent clouds without special equipment. Their cradle is located at an altitude of 70 to 80 km above sea level.

Why and how do clouds appear?

But how are clouds formed? For children, this is a very important issue. To answer it, you need to get acquainted with another interesting physical phenomenon- condensation. What is it?

We have all seen more than once how steam comes out of the spout of a boiling kettle. If you substitute a cold saucer under this stream, then droplets of water will appear on its surface. This phenomenon is called condensation.

Approximately the same processes take place in the upper layers of the atmosphere. Water vapor, rising higher and higher, cools and begins to condense into liquid droplets, from which clouds form. The size of these droplets is incredibly small - 100, and sometimes 1000 times less than 1 mm. If the steam manages to rise very high, then it will turn not into a liquid, but into a solid state. Therefore, in the uppermost layers of the atmosphere, clouds consist of tiny pieces of ice.

But in order for the steam to begin to condense, only lowering the temperature is not enough. The center of each droplet or crystal is the smallest speck of dust, around which moisture has collected.

By the way, it is for this reason that very large clouds can often be observed over cities where there are a lot of cars or large factories. Indeed, in such places there are much more different air polluting particles in the atmosphere than in sparsely populated areas of our planet.

Why do clouds fly?

From the surface of the Earth, clouds seem so light and airy. In fact, they can weigh many tons. How can a whole cloud of water, consisting of a huge accumulation of water droplets, stay in the air? Everything is very simple. The size of each droplet is so small that even a small stream of air rising from the Earth stops them from falling.

Scientists have calculated that the updraft speed to hold the cloud could be as low as 50 cm per second. If we translate this number into a more understandable form, we get a very small value - 1.8 km / h. And this is much less than the speed of a pedestrian.

What are clouds?

Beautiful white mountains floating in a bright blue sky are always a delight to the eye. But why do they seem like this?
It turns out that the more sunlight passes through the clouds, the whiter they appear to us from Earth. A gray overcast sky only means that the cloud layer is very dense and the sun's rays practically do not pass through it. But black clouds most often just contain a lot of dust. Cloud formations of this color often appear again over industrial areas, where air pollution is most severe.

But clouds differ not only in color, but also in shape. The common name for clouds usually describes their appearance. Although scientists have come up with a very complex classification of clouds, only three types of clouds can be clearly distinguished.

It is this type of accumulation of water vapor in the sky that we most often call clouds. These are the very dazzling white giants, smoothly changing their shape. It is for them that people like to watch, imagining who they look like. Such cloudiness does not bother at all. And this is not surprising, because cumulus clouds are the companions of good weather.

Stratus clouds are not so beautiful anymore. Most often they gray color a variety of shades. Such clouds are quite dense and consist exclusively of droplets ready to fall to the Earth. They swim not so high above the surface. In this case, the height of the clouds above the ground is about 1-2 km.

If the sky is covered with stratus clouds interspersed with cumulus clouds, then it's okay - the weather is unlikely to deteriorate. This type of cloudiness is often also called stratocumulus clouds. By the way, exactly similar view clouds appears before the mind's eye when you need to answer the question: "What is cloudiness?". But a solid gray blanket always suggests a long and tedious rain.

And this kind of clouds is located quite high. They can be observed at about seven kilometers altitude. They look like lambs or strokes of oil paint smeared in the sky.

Such cloudiness indicates an imminent change in weather not in better side. By the way, cirrus clouds are the most photogenic. The photos in which they are present look incredibly impressive.

The clouds are very heavy. On average, their weight is about 10 tons. In addition, they also have huge size. A single cloud can extend over 10 km, and thunderclouds can extend the same distance in height.

The duration of the "life" of clouds depends on the humidity of the air. With normal humidity, a cloud can exist for a very long time. But at low temperatures, the droplets of water that make up the cloud will begin to evaporate quickly and it can live no more than 15 minutes.

It is hard to imagine, looking at the clouds floating across the sky, that this miracle of nature can be created at home. Although in fact a real cloud can be made artificially. True, this requires special equipment. I came up with how to make clouds by the Dutch artist Berndnaut Smilde. His homemade clouds do not last long, about 10 seconds. But during this time they can be photographed or filmed at the moment of the birth of a small cloud.

Such a phenomenon as cloudiness is observed not only on Earth, but also on several other planets. solar system. Clouds have been detected in the atmosphere of Venus and Mars, as well as on the satellites of Saturn - Titan and Neptune - Triton.

In 2004, several meteorologists and physicists came together to form international organization Society of Cloud Lovers. They not only admire these bizarre creatures themselves earth's atmosphere, but also encourage everyone to raise their eyes to the sky to admire the beautiful and diverse clouds.

Surprisingly, even scientists do not know everything about clouds. Their study is still ongoing. Both in Russia and in the USA, programs are still working to find out all the properties of these beautiful, snow-white, airy islands.

The concept of "cloudiness" refers to the number of clouds observed in one place. Clouds, in turn, are called atmospheric phenomena formed by a suspension of water vapor. The classification of clouds includes many of their types, divided by size, shape, nature of formation and altitude.

In everyday life, special terms are used to measure cloudiness. Expanded scales for measuring this indicator are used in meteorology, maritime affairs and aviation.

Meteorologists use a ten-point cloud scale, which is sometimes expressed as a percentage of coverage of the observable sky (1 point - 10% coverage). In addition, the height of cloud formation is divided into upper and lower tiers. The same system is used in maritime affairs. Aviation meteorologists use a system of eight octants (parts of the visible sky) with a more detailed indication of the height of the clouds.

To determine the lower boundary of the clouds is used special device. But only aviation weather stations are in dire need of it. In other cases, a visual assessment of the height is made.

Cloud types

Cloudiness plays an important role in the formation weather conditions. Cloud cover prevents the Earth's surface from heating and prolongs the process of its cooling. Cloud cover significantly reduces daily temperature fluctuations. Depending on the amount of clouds at a certain time, several types of cloudiness are distinguished:

1. "Clear or partly cloudy" corresponds to cloudiness of 3 points in the lower (up to 2 km) and middle tiers (2 - 6 km) or any amount of clouds in the upper (above 6 km).
2. "Changing or variable" - 1-3/4-7 points in the lower or middle tier.
3. "With clearings" - up to 7 points of total cloudiness of the lower and middle tiers.
4. "Overcast, cloudy" - 8-10 points in the lower tier or not translucent clouds on average, as well as with precipitation in the form of rain or snow.

Types of clouds

The world classification of clouds distinguishes many types, each of which has its own Latin name. It takes into account the shape, origin, height of education and a number of other factors. The classification is based on several types of clouds:

• Cirrus clouds are thin filaments of white. They are located at an altitude of 3 to 18 km, depending on the latitude. Consist of falling ice crystals, to which they owe their appearance. Among the cirrus at a height of over 7 km, clouds are divided into cirrocumulus, altostratus, which have a low density. Below, at an altitude of about 5 km, there are altocumulus clouds.
• Cumulus clouds are dense formations of white color and a considerable height (sometimes more than 5 km). They are located most often in the lower tier with vertical development in the middle. Cumulus clouds at the upper boundary of the middle tier are called altocumulus.
• Cumulonimbus, shower and thunderclouds, as a rule, are located low above the Earth's surface 500-2000 meters, are characterized by precipitation precipitation in the form of rain, snow.
• Stratus clouds are a layer of low-density suspended matter. They let in the light of the sun and moon and are at an altitude of between 30 and 400 meters.

Cirrus, cumulus and stratus types, mixing, form other types: cirrocumulus, stratocumulus, cirrostratus. In addition to the main types of clouds, there are other, less common ones: silvery and mother-of-pearl, lenticular and vymeform. And clouds formed by fires or volcanoes are called pyrocumulative.

Deformed cirrocumulus clouds.

Sometimes rounded breaks can be observed in cirrocumulus clouds. Such a gap is formed when the temperature in the cloud is below zero, but the water has not yet had time to freeze. When water begins to freeze in one place, the nearby water vapor quickly evaporates and condenses on ice crystals. Ice crystals become heavy and under their own weight can settle to the ground. Thus, deformed cirrocumulus clouds are obtained.

Cirrostratus clouds (Cirrostratus, Cs) - a type of clouds of the upper tier.
Color: whitish, translucent.
Description and shape of the cloud . Cirrostratus clouds are in the form of a continuous veil high in the sky. In the presence of these clouds, the sun and moon float as if in a haze. The transparency of clouds can vary depending on the density of the cloud. At low density, the halo effect is also observed. The thickness of cirrostratus clouds can reach 2-6 kilometers.
Visibility inside the cloud : 50-200 meters.
Composition and education. The source of material for the formation of cirrostratus clouds is entire layers of air rising upward as a result of multilevel convergence. The cloud element is ice crystals.
Precipitation does not fall out of them, but thickening of cirrostratus clouds can serve as a harbinger of bad weather.

What are the middle tier clouds in shape:

• altocumulus clouds,

• altostratus clouds,

• Altostratus translucent clouds.

Altocumulus (Altocumulus, Ac
Color : white, gray or bluish white.
Description and shape of the cloud . Altocumulus clouds are usually summer time. They are arranged in waves or in ridges in the form of flakes or plates. There are gaps between individual elements. Sometimes around these clouds there is a beautiful phenomenon called "iridization" . This is the iridescent coloration of the edge of the cloud.
Visibility inside the cloud : 50-80 meters.
Composition and education. Formed when warm air rises. The rise can be provoked by the onset of a cold front, which displaces air heated near the surface of the earth upward.
Cloud weather prediction. Appear after a thunderstorm or storm. They predict clear weather.

Altostratus clouds (Altostratus, As) - a type of middle tier clouds.
Color : gray or bluish.
Description and shape of the cloud . Altostratus clouds are in the form of a uniform or slightly wavy veil through which the sun and moon faintly shine through. Cloud height varies from one to four kilometers.
Visibility inside the cloud : 25-40 meters.
Composition and education. The main cloud elements are ice crystals, snowflakes, supercooled water.
Cloud weather prediction. Precipitation falls from altostratus clouds. This is heavy rain or snow.

Altostratus translucent clouds (Altostratus translucidus, As trans) - a type of middle tier clouds .
Color : white-bluish.
Description and shape of the cloud . Clearly visible translucent wavy stripes. The solar and lunar disks are quite distinct. Despite this, they cast a faint shadow on the ground. The lower boundary of these clouds is at an altitude of 3-5 km. The height of the cloud array is 1-2 km. Gradually cover the entire sky with a continuous veil.
Cloud weather prediction. Precipitation also falls from altostratus translucent clouds, but in summer period rarely reach the earth's surface.

What are the clouds of the lower tier in shape:

• layered clouds,

• stratocumulus clouds,

• Cumulus clouds.

Stratus clouds (Stratus, St) - a type of clouds of the lower tier.
Color : dark gray or light gray.
Description and shape of the cloud . Layered clouds are in the form of a homogeneous whitish veil that covers the entire sky and looks like fog. The height of the cloud is small - from several tens to hundreds of meters. The lower part can drop very low, and then the cloud merges with the fog. Formed in the lower troposphere.
: 100-400 meters, sometimes drops to 30-90.
Cloud weather prediction. Stratus clouds occasionally produce precipitation. It's drizzle or snow grains, depending on the season.

Stratocumulus clouds (Stratocumulus, Sc) - a type of clouds of the lower tier.
Color : grey.
Description and shape of the cloud . Stratocumulus clouds are in the form of massive ridges, waves, plates. They can be both with gaps, and tighten the sky with a continuous wavy veil. The height of the cloud layer is from 200 to 800 meters. Quite dense, the sun shines through only at the edges of the clouds.
Height above ground : 500 to 1800 meters.
Compound . The main cloud element is water drops.
Cloud weather prediction. Precipitation is possible only occasionally, and even then short.

Striped stratocumulus clouds.
Color : grey.
Description and shape of the cloud . A variety of stratocumulus clouds. They are notable for the fact that they are located in the sky in the form of regular rows or waves separated by gaps.
Height above ground : 500 to 1800 meters.
Compound . The cloud element is water drops.
Cloud weather prediction. Most often they portend good weather.

Cumulus clouds (Cumulus, Cu) - a type of clouds of the lower tier.
Color : bright white.
Description and shape of the cloud . Dense, elongated clouds. The upper part of cumulus clouds is rounded or in the form of round turrets.
Height above ground : from 800 to 1500 meters, occasionally more than two kilometers.
Cloud weather prediction. If they are located separately, far from each other, then to good weather. But if the cumulus clouds are large and multi-storey, then there may be a heavy downpour.

What are the clouds of vertical development in shape:

• nimbostratus clouds,

• Cumulonimbus clouds.

Nimbostratus clouds (Nimbostratus, Ns) - a type of clouds of vertical development.
Color : dark gray, with a bluish tint.
Description and shape of the cloud . Clouds cover the earth in a continuous veil. Nimbostratus clouds are heterogeneous structure, sometimes wavy. The thickness of the layer is up to several kilometers. They differ from stratus clouds in their heterogeneous structure, which becomes blurred during rain or snow. But in the intervals between precipitation, the heterogeneity again becomes discernible.
Height above ground : 100 to 1900 meters.
Cloud weather prediction. They produce heavy rainfall.

Cumulonimbus (Cumulonimbus, Cb) - type of clouds of vertical development .
Color : thick dark grey.
Description and shape of the cloud . Powerful dense clouds reaching a height of more than 10 km. Clouds are preceded by a squally wind, a hurricane. They are distinguished by a flat top - an "anvil", consisting of ice crystals.
Height above ground : up to 2000 meters.
Compound . At the base - water drops, and at the top, where the temperature is much lower - ice crystals.
Cloud weather prediction. Cumulonimbus clouds are the harbinger of bad weather. They bring heavy rain, thunderstorms, hail is possible.

This completes the enumeration of the main types and the shape of the clouds, but there are other, rarer types. They cannot be assigned to any of the above categories, therefore they are considered separately. In the next article, we will answer the question: What other clouds are there?

It was the article "Types and forms of clouds. What are clouds?" Read further:

1. Classification of clouds.

2. Microphysics of clouds.

3. Light phenomena in clouds.

4. Electricity of clouds and precipitation.

5. Daily and annual course of cloud cover.

1. Cloud classification

Clouds are one of most interesting phenomena nature. In that complex complex of elements and phenomena, which is united by the concept of weather, clouds play a decisive role. They change the thermal and radiation regime of the atmosphere and thus have a great influence on many aspects of human activity. First of all, for agriculture, forestry, different kinds transport (especially aviation). Until now, clouds and fogs significantly affect the takeoff, landing and flight of the aircraft. The flight of an aircraft in the clouds is accompanied by:

severe deterioration in visibility;

the occurrence of glaciation;

"chatter" (a consequence of developed turbulence).

Cloud - a visible set of suspended drops of water or ice crystals located at a certain height above the earth's surface.

Cloud - fog in height (V.I. Dal).

From the point of view of the microphysical structure, there is no fundamental difference between clouds and fogs. But they differ significantly in the conditions for the formation of vertical power, water content and other parameters.

Clouds - systems suspended in the atmosphere (not at the very surface of the earth) products of condensation (condensation) of water vapor - drops of water, ice crystals, both of them. They are called cloud elements (Meteorological Dictionary, 1974).

Clouds form as a result of the condensation of water vapor in the atmosphere. They are formed either as a result of a general increase in the moisture content in the atmosphere, or under the influence of a decrease in air temperature. And in real conditions, both of these factors play a role. The decrease in temperature can occur as a result of adiabatic cooling, radiation, and turbulent mixing.

The lifetime of a cloud can vary widely. A cumulus cloud can exist for 10–15 minutes, another for several hours. As long as the cloud exists, a continuous process of cloud formation takes place in it: some elements evaporate, others fall out, and still others reappear.

The variety of cloud forms observed in nature in all possible combinations is the result of complex processes developing in the atmosphere.

The structure of clouds and the precipitation associated with them can be used to judge the state of the atmosphere on this moment and (more importantly) about its upcoming changes. By the way, before the beginning of systematic aerological sounding, clouds were an important element of the so-called indirect aerology, since clouds were used to judge processes in the lower half of the troposphere.

Clouds are classified according to several criteria:

by the phase state of cloud elements;

according to the shape and height of the location;

by origin.

By phase state Cloud cloud elements are divided into classes:

water (drip);

mixed;

ice (crystalline).

Water (drip) clouds are made up of drops only. They can exist both at positive and at negative (down to -10°C and below) temperatures. These are altocumulus, stratus, cumulus.

mixed Clouds are made up of a mixture of supercooled droplets and ice crystals. They can exist, as a rule, at temperatures from -10 to -40°C. They are formed as a result of the appearance of crystals in a water cloud, or as a result of crystals entering a water cloud from outside. Mixed clouds give precipitation. These are highly stratified, nimbostratus, cumulonimbus; at low temperatures sometimes also Altocumulus, Stratocumulus, Stratocumulus.

Ice (crystalline) clouds are composed of ice crystals only. They can only exist at temperatures below -40°C. These are all clouds of the upper tier: cirrus, cirrostratus, cirrocumulus, as well as the tops of cumulonimbus clouds.

Shape and height cloud forms in the troposphere are diverse and changeable. But they can be reduced to a relatively small number of types. The first and most successful classification of clouds was proposed in 1803 by the English pharmacologist Luke Howard. Until now, it is considered unsurpassed. It turned out to be so simple and accurate that it is still used by meteorologists. At the end of the 19th century, an international classification of clouds was adopted. Since the 80s of the 19th century, photographs have been used in compiling the classification of clouds. They are currently combined in the International Cloud Atlas. In the modern version of the international classification, clouds are divided into

Three types: pinnate, stratus, cumulus;

Ten genera (forms) - a combination of three types;

In each form, types, varieties and additional features are distinguished.

Top 10 Cloud Shapes

According to the location height: clouds are conventionally divided into three tiers: upper, middle and lower (Table 8). They also distinguish clouds of vertical development: the base of these clouds lies in the lower tier, and the top lies in the middle or upper tier.

Table 8 - Height of clouds of different tiers depending on latitude, km

a brief description of various forms clouds

Upper tier - icy, white, not obscuring the Sun.

Spindrift clouds(Ci) consist of separate pinnate elements in the form of thin white threads or white tufts and elongated ridges. They have a fibrous structure and a silky sheen. because of strong winds they have a characteristic shape of elongated, disheveled "mare's tails". They have a significant vertical extent (on the order of hundreds of meters).

Types: filiform, claw-like, tower-shaped, dense, flaky.

Varieties: mixed, radial, spinal, double.

cirrocumulus clouds(SS) - high and fluffy, consisting of separate formations (very small grains, flakes, balls, curls). They resemble ripples on the surface of water or sand. Often they form beautiful regular waves: "the sky in the lambs".

Varieties: wavy, perforated.

Sometimes they give falling streaks.

Cirrostratus clouds(Cs) : ice veil, thin, milky white, transparent. The sun shines through them so brightly that rings (halos) appear around it, and sometimes false suns. The thickness of the layer is from hundreds of meters to a kilometer.

Species: filamentous, foggy.

Varieties: double, wavy.

middle tier

Altocumulus clouds(Aс) at medium heights they look like flakes or ridges of white or gray color. Unlike cirrocumulus clouds, which are higher up, they always have darker edges. These are fairly thin clouds. Altocumulus clouds are characterized by such optical phenomena as iridescence and crowns.

Species: layered, lenticular, turret-shaped, flaky.

Varieties: translucent, with gaps, double, wavy, radial, perforated.

Features: streaks of fall, vymeobrazny character.

Highly layered(As) cover the firmament in whole or in part. Through separate clouds, less dense, the Sun or the Moon can shine through. In this case, they are visible as if through glass, in the form of blurry spots. These are typical mixed clouds. They give light rainfall. The halo is not observed.

The types are not different.

Varieties: translucent, non-translucent, double, wavy, radial.

Features: the lower surface sometimes has a vyme-like appearance; patches of lower clouds are often observed under the As layer.

lower tier

Nimbostratus(Ns): gray cloud cover, often gloomy in appearance, appearing washed out. The layer of clouds is more powerful than that of high-stratus, so the Sun and Moon do not shine through them. These clouds are in the lower and middle, and often in the upper tiers. These are mixed clouds: in the lower part they consist of large drops and snowflakes, and in the upper part they consist of small drops and small snowflakes (like As).

Species and varieties are not distinguished.

Features: fall streaks, cloud wisps.

Stratocumulus(sc) often formed from upper cumulus clouds as they rise and spread outward. When viewed from an airplane, they look like a wavy blanket of ridges and ledges with gaps. Rolls, discs, slabs are white in color but always with darker areas, are longer than Ac (> 5°). These are water (droplet) clouds, so they do not give precipitation.

Species: layered, lenticular, turret-shaped.

Varieties: translucent, with gaps, non-translucent, double, wavy, radial, perforated.

Features: vymeiform, structure of the lower surface.

layered(St) are aqueous or mixed, appearing as a uniform gray layer. At low density, the Sun shines through them, while it has a clear outline. Drizzle can fall from stratus clouds, and in winter - ice needles, fine snow, snow grains. The thickness of the layer is up to several hundred meters.

Species: foggy, broken.

Varieties: non-translucent translucent, wavy.

Clouds of vertical development

Cumulus(cu) dense clouds with sharply defined contours. They develop upwards, forming dense white tops, similar to cauliflower, the bases of the clouds are relatively dark. Vertical power varies widely:

for flat ones - tens and hundreds of meters;

powerful ones - more than 5 km.

These are water clouds (consisting of drops), so they do not give precipitation (with the exception of the tropics, where small rains can fall from powerful cumulus clouds).

Types: flat, medium, powerful, broken.

Varieties: radiating.

Features: hat, fall stripes.

Cumulonimbus(CB) larger and darker, the result of further development of cumulus vertically. The vertical thickness of cumulonimbus clouds can vary from 3 to 15 km. They greatly change the illumination (reduce) as they cover the Sun. These are mixed clouds: in the lower part there are drops, in the middle - drops and crystals, in the upper part - crystals. It is with Cb that showers, thunderstorms, squalls, and tornadoes are associated. Rare in polar latitudes.

Species: bald, hairy.

Peculiarities: fall stripes, tatters, anvil, protrusions, hat, veil, collar, occasionally trunk.

Origin allocate genetic types of clouds:

Intramass

a) convection clouds, b) clouds of stable masses.

Frontal

a) upward sliding clouds, b) orographic clouds.

In the first genetic type (intramass), they distinguish convection clouds and clouds of stable air masses.

clouds of convection arise as a result of air cooling in vertical ascending currents. In the first stage of development of thermal convection, when it is only a kind of turbulent motion, these are flat cumulus clouds, as well as fractocumulus; when well-formed ascending currents of significant speed (3.6 m/s or more) arise, powerful cumulus and cumulonimbus clouds appear. In the middle tier, some varieties of altocumulus clouds are associated with convection: tower-shaped and flaky.

Cumulus, or convective, clouds look like isolated cloud masses. They are strongly developed vertically and have a small (medium) extent horizontally.

As a result of uneven heating of the earth's surface by the Sun, "bubbles" of warm air are formed in some places, which rise up and fall into layers of colder air (thermals). There they cool down, the water vapor in them condenses, and clouds form (Figure 30). These bubbles, or convection cells, live no more than 20 minutes, with rare exceptions. Often several cells form in one place, then the cloud can last for about an hour.

According to studies by photogrammetry from the ground and during observations in flights, a convective cloud consists of separate flows that have the form of a jet or thermal (bubble). On average, the diameter of the jets at the earth's surface (and up to a height of about 3000 meters) is 60 meters, and the average concentration of streams is 40 jets per 1 km 2. The sizes of convective flows in powerful cumulus clouds are much larger than outside them (in the cloud d ~ 90 m, under it - 50 m).

Figure 30 - Scheme of the occurrence of thermal convection (Clouds, 2007)

In connection with the development of a convective cloud in the troposphere, the following levels are distinguished:

a) the level of condensation, practically coincides with the lower boundary of the cloud; Zk

b) the level of the zero isotherm separating the supercooled (upper) part of the cloud from the non-supercooled one; Zo

c) the level of free convection, which practically coincides with the upper boundary of the cloud.

Layers with temperature inversions delay convection and prevent further development of cumulus tops.

Dynamic convection is caused by the forced rise of warm air when flowing around an obstacle. The role of an obstacle can be performed by a mountain range (Figure 31) or a frontal surface with a steep angle of inclination.

Convection clouds develop in unstable air masses (in cold high altitudes moving over a warm surface; local high altitudes over land in summer) are called cumulus (not cumulus).

Clouds of persistent air masses arise in connection with the cooling of air from the underlying surface, dynamic turbulence and wave motions in the atmosphere. This cloud subtype includes stratus, stratocumulus, and altocumulus. They have a pronounced wavy structure, therefore they are called wavy.

Figure 31 - Scheme of the occurrence of dynamic convection when the air flows over the ridge (Oblaka, 2007)

In the atmosphere, wave motions of very different amplitudes and wavelengths are observed. Under the influence of such movements, under certain conditions, wavy clouds can form, which have the form of a horizontally distributed (tens and hundreds of kilometers) layer consisting of disks, plates, shafts (Figure 32). These clouds have, on average, a small vertical thickness (several tens or hundreds of meters), but in some cases up to 2–3 km.

Figure 32 - Scheme of the formation of wavy clouds under the inversion layer

(Clouds, 2007)

According to modern data, wavy clouds are formed as a result of the transfer of clouds of other forms from areas of low pressure to areas of increased pressure and their further transformation. Under the existing clouds, an inversion layer is formed as a result of downward air movements. In addition to free waves, forced standing waves can occur in the atmosphere over mountains through which air flows. In this case, clouds of obstacles are formed.

frontal clouds . In connection with the fronts, huge cloud systems arise, stretched along the front line for thousands of kilometers and a width of hundreds of kilometers. Such clouds are called upslip clouds. The front separates a gentle wedge of cold air from a layer of warm air lying next to it and above it. Warm air slowly rises along the cold wedge, which leads to adiabatic cooling of thick layers and condensation of water vapor (Figure 33). The result is a powerful cloud layer. Such clouds are called layered. The largest thickness (several kilometers) are nimbostratus clouds. Farther from the front line, they are replaced by highly stratified, pinnately stratified. At a distance of many hundreds of kilometers from the front line, ridges of cirrus clouds are observed. Frontal clouds can intensify as the front approaches a mountain range.

Figure 33 - Scheme of the formation of clouds of upward sliding (Clouds, 2007)

In addition, there are:

Volcanic eruption clouds are cumulus-shaped clouds that form over volcanoes during eruption. They are characterized by rapid development, abundant clubs. They consist of dust (ash) and water droplets, sometimes they give precipitation. Electrical phenomena may be associated with them.

Damping clouds (deceleration of horizontal air transfer when moving it to the underlying surface with increased friction, especially in front of mountain ranges and massifs).

Clouds of fires - are formed due to the formation of strong upward convection currents over large (forest) fires. Contain products of combustion (smoke, soot, ash). They often look gloomy.