What is above the clouds. What are clouds formed from and what types are they divided into? Clouds of vertical development

Based on their origin, clouds come in several genetic types. There are intramass clouds formed inside homogeneous air masses and frontal - at the boundaries of interaction of two air masses with different properties.

A. Clouds of intramass origin. As a result of convection, which develops when a non-uniform surface is heated in unstable air masses, convection clouds appear - cumulus clouds. The more intense the convection, the greater the power of cumulus clouds. They can form cumulus rain clouds. Downward currents are observed on the sides of the clouds. These clouds are most developed in the afternoon and disappear at night.

In stable air masses (warm), the leading one is the turbulent upward transport of water vapor and its adiabatic cooling.

B. Frontal type clouds. Occurs when warm and cold air masses meet at atmospheric front. Warm air rises along a wedge of cold air. The slow rise of warm air leads to its adiabatic cooling and condensation of water vapor. The result is a complex cloud system that spans all cloud tiers. The thickest part of the system (5-6 km high) is located near the front (nimbostratus Ns).

The inversion layer delays this transfer. Under the inversion layer, water vapor accumulates and is radiatively cooled. Clouds with a wavy structure appear (stratus, stratocumulus, altocumulus).

At high altitudes, where the temperature of the rising air drops below 0ºC, ice crystals appear in the clouds. Crystals can exist together with drops, so thick layers of water-glacial clouds are observed.

Clouds are divided into:

- water– consisting of water droplets;

- icy– consist of crystalline ice;

- mixed– containing both water droplets and ice crystals.

In the warm season, water clouds form mainly in the lower layers of the troposphere, mixed in the middle, and ice in the upper.

According to the international classification, clouds are divided according to their height and appearance.

Clouds are divided into four families based on their height:

1. I. upper level clouds located at altitudes above 6000 m (CH);
2. II. mid-level clouds located at altitudes from 2000 to 6000 m (CM);
3. III. low level clouds below 2000 m (CL);
4. IV. clouds of vertical development. The base of these clouds is at the level of the lower tier, and the tops can reach the position of the clouds of the upper tier.

Based on their appearance, clouds are divided into 10 genera. The genera are distributed among families as follows:

Upper tier:

1. CirrusCirrus(Ci) - look like separate threads, ridges or strips of fibrous structure;
2. Cirrocumulus Cirrocumulus(Cc) – ridges or layers having a structure of very small flakes, balls, curls (lambs);
3. CirrostratusCirrostratus(Cs) - a thin transparent whitish veil partially or completely covering the sky.

All upper level clouds are icy.

Middle tier:

1. AltocumulusAltocumulus(Ac) – cloud layers or ridges of white or gray. Consist of tiny droplets of water.
2. High-layeredAltostratus(As) - can penetrate into the upper tier, have greater thickness, milky gray cloud cover completely covering the sky. Refers to mixed clouds. They produce light drizzle or fine snow precipitation.

Lower tier:

1. StratocumulusStratocumulus(Sc) – ridges or layers of blocks and shafts of gray color. Water, give light precipitation in the form of drizzle, do not give precipitation when supercooled;
2. LayeredStratus(St) – the lowest clouds in the form of a uniform gray color. The clouds are watery, and precipitation falls in the form of drizzle, fine snow, and cereals.
3. NimbostratusNimbostratus(Ns) – shapeless, gray in color with great power. Mixed clouds produce continuous precipitation.
4. CumulusCumulus(Cu) - dense cloud puffs and heaps with sharply defined contours and an almost horizontal base. Water, do not give precipitation.

10. CumulonimbusCumulonimbus(Cb) - powerful cumulus-shaped masses, very strongly developed vertically in the form of mountains and towers. Their tops are flattened. In the upper part they are ice, in the lower part they are water. They produce showery precipitation, sometimes with hail. They are associated with thunderstorms, so they are often called thunderstorms or thunderstorms.

Types of clouds and the altitude at which they form in mid-latitudes

Cloud formation is also possible outside the troposphere, but they have been studied much less. For example, nacreous clouds can be observed in the stratosphere, and noctilucent clouds can be observed in the mesosphere.

Literature

1. Zubaschenko E.M. Regional Physiography. Earth's climates: teaching aid. Part 1. / E.M. Zubaschenko, V.I. Shmykov, A.Ya. Nemykin, N.V. Polyakova. – Voronezh: VSPU, 2007. – 183 p.

Another foray into our favorite global network puzzled me. The more I read, the more I understand how interesting the simplest and most banal things can be.

Take the clouds, for example. Who didn’t dream of riding them as a child? We believed it was possible. After all, they are probably soft and pleasant to the touch.

Later, while studying physics, each of us was disappointed when we learned the nature of clouds. It turned out that clouds are not soft, fluffy and pleasant. These are water droplets or ice crystals in the atmosphere. They are also often called cloud elements. What does it have to do with it, it turns out? different temperatures cloud composition may vary. Clouds consist of water droplets if the air temperature exceeds?10 °C. These are ordinary rain clouds. If it is lower than that, but higher than 15 °C, then the clouds include both droplets and small crystals. By the way, these are the clouds that send us sleet or sleet. When the temperature in the cloud is below?15 °C, the cloud consists entirely of crystals, which turn into snowflakes.

However, the crystals and droplets in the cloud are very small. Where do the huge flakes of snow and large drops come from? spring rain? Everything is quite simple. Gradually the number of elements in the cloud increases. The elements merge with each other, forming droplets and snowflakes. The clouds increase and when they reach a critical mass, precipitation begins to fall.

Precipitation usually does not fall from homogeneous clouds, but from those that have a mixed composition of at least one layer. These are, for example, cumulonimbus, nimbostratus, and altostratus. Although light precipitation in the form of drizzle or light fine snow can also fall from homogeneous clouds, for example, from stratus clouds.

Most often, clouds form and are observed in the lower layer of the atmosphere, called the troposphere. Less commonly, clouds are observed at an altitude of 20-25 kilometers. Such clouds received a special name - mother-of-pearl clouds. Very rarely clouds climb to a height of 70-80 kilometers. They also have their own name - silver.

Despite the huge number of various bizarre forms of clouds in the traposphere, classifying them is quite simple. Even in appearance.

Cirrus clouds (Cirrus, Ci).

In appearance, these are perhaps the lightest and most fragile clouds. They consist of thin white threads or shreds. Such clouds always have the shape of elongated ridges. These are perhaps the highest altitude trapospheric clouds. Usually seen in upper layers traposphere (from 3 to 18 km above the earth, depending on latitude). These clouds are notable for the fact that they can have a fairly large vertical extent (from hundreds of meters to several kilometers). Visibility inside the clouds is not very high: only 150-500 meters. The reason for this is that such clouds consist of fairly large ice crystals. Because of this, they have a noticeable fall rate. However, due to the wind, we see not vertical stripes, but shifted and bizarrely curved filaments of cirrus clouds.

Interestingly, such clouds often move ahead of a warm air mass. They also often accompany anticyclones. And sometimes they are even banal remnants of cumulonimbus clouds.

It is very interesting that the appearance of such clouds may indicate the upcoming heavy rain in about a day.

Cirrus clouds are also divided into several subspecies.

Cirrocumulus (Cirrocumulus, Cc).

These clouds are located as high as the previous view. We will never see precipitation from such clouds. It is interesting that when such clouds appear, one can safely say that in a few hours a thunderstorm with showers is possible. And sometimes there is a storm.

Such clouds are nicknamed “lamb” for their intricate shapes in the form of small groups or rows of balls. Very often observed with cirrostratus and cirrus.

The height of the lower border is slightly higher than that of the previous view. It extends approximately 6-8 kilometers from the earth. The vertical length reaches a kilometer. However, visibility inside is much higher than cirrus clouds - from 5.5 to 10 kilometers.

In such clouds a very interesting phenomenon is observed - iridization. It lies in the fact that the edges of the clouds acquire a rainbow color, which in itself is very beautiful.

Cirrostratus clouds (Cirrostratus, Cs).

These clouds are made of ice crystals. They are very easy to recognize: they represent a uniform whitish veil covering the sky. They usually appear almost immediately after their feathery counterparts. Although their height is the same as that of previous species, vertically they are much longer than their counterparts. Their length ranges from 2 to 6 kilometers. Visibility inside the cloud is very low: from 50 to 200 meters. Like the previous two types, the appearance of such clouds promises a quick change in the weather. They are followed by rain and thunderstorms. Why, you ask? It's simple. All of the above types of clouds move ahead of a warm air mass that contains a lot of moisture. And she, in turn, is the source of rain.

Despite the fact that the clouds cover the sky with a veil, the light of the Sun and Moon can pass through them. In this case, the rays are often distorted and such an interesting phenomenon as a halo is formed. It is a luminous ring around the Sun or Moon. But, unfortunately, this beautiful phenomenon is very short-lived, since the clouds very quickly begin to thicken.

An interesting fact is that the halo circle was popularly an omen of imminent rain. People believed that it was the Moon or the Sun that washed itself. And after the water procedures, the luminaries, according to legend, poured soda onto the ground.

Altostratus clouds (Altostratus, As).

Outwardly, they appear as a gloomy grayish or blue-gray veil, through which the sun sometimes peeks through, albeit in the form of a shapeless blurry spot.

These clouds live, so to speak, lower than their counterparts already discussed, at approximately 3-5 kilometers above sea level. But they are also quite long vertically - from 1 to 4 kilometers. Visibility in them is very low - 25-40 meters. The composition of these clouds is heterogeneous. It contains both crystals and droplets of water, albeit supercooled.

Unlike all of the above types, precipitation always falls from these clouds in the form of rain or snow at any time of the year. Interestingly, rain from such clouds does not reach the ground, but evaporates during the flight.

These clouds are followed by the appearance of their rain stratus counterparts.

Altocumulus clouds (Altocumulus, Ac).

These clouds are harbingers of imminent showers. They have the shape of small balls or sheets, which are arranged in rows or collected in separate groups. Their colors are very different: from white to blue. Their length is small - only a few hundred meters. Apparently the visibility is also rather weak: only 50-70 meters. They are located in the middle layers of the stratosphere, approximately 2 to 6 kilometers above the earth. In addition to rain, such clouds bring with them cold temperatures.

Nimbostratus clouds (Nimbostratus, Ns).

These are gloomy dark gray clouds that are a continuous layer. It seems that there is no end to it. Everywhere there is a cloudy sky from which rain is constantly pouring. This goes on for quite some time.

They are much darker than their layered counterparts. Unlike all the clouds described above, these are located in the lower layers of the stratosphere. They hover almost above the ground at a distance of 100 meters, although their thickness can be up to several kilometers.

The movements of these clouds are accompanied by strong and cold wind, the temperature drops.

Stratus clouds (Stratus, St).

This type of cloud is very similar to fog. They are located very low above the ground. The lower limit does not exceed hundreds of meters. Sometimes, when clouds fly very low, they can merge with ordinary fog.

Their maximum thickness is hundreds of meters. These clouds don't always bring rain. As soon as they thicken and become stronger, they will shed precious moisture onto the ground. In this case, the rain will not be very heavy and much shorter than the rain of nimbostratus clouds.

Stratocumulus clouds (Stratocumulus, Sc).

Such clouds do not always bring precipitation with them. They are formed when cold air replaces warm air. In this case, moisture is not released, but rather absorbed. And there is no rain. They are predominantly gray in color and are presented in the form of large waves and ridges, between which there are small gaps. They have an average width of 200-800 meters.

Cumulus clouds (Cumulus, Cu).

They are sometimes called good weather harbingers. This is the type of cloud we see most often. White, bright, in the form of all kinds of figures, they amaze and develop our imagination. They have the shape of a dome with a flat base or towers with rounded outlines. It is noteworthy that they are very wide - up to 5 kilometers or more.

Cumulonimbus clouds (Cumulonimbus, Cu).

These are very powerful clouds. Sometimes their width reaches 14 kilometers. These are clouds of thunderstorms, showers, hail and heavy winds. The word most often used for these clouds is “clouds.” Sometimes they line up in what is called a squall line. Interestingly, cloud composition varies depending on altitude. If the lower layers consist mainly of water droplets, then the upper ones consist of ice crystals. They develop from powerful cumulus clouds, and their appearance does not bode well.

By the way, clouds exist not only on our planet. It turns out that wherever there is a gas shell, there are clouds. But they do not consist of water, but, for example, of sulfuric acid.

Here's a video showing the different clouds: (amazingly beautiful!)

Well, that’s probably all I wanted to write about these white-maned horses this time.

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 also what types of clouds there are...

Masses of water vapor transported 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 the process that provides fresh water everything alive on .

As the steam rises, it cools and turns back 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 the Earth, and the cycle repeats.

How are clouds formed?

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

If the air contains the maximum amount of water vapor possible for a given temperature, it is considered “saturated”, and its “ relative humidity" is equal to 100%. The "dew point" is the corresponding temperature. The process of water vapor changing into a solid or liquid state that occurs when 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 flowing over hills. At the same time, using part of its heat, it expands due to a drop in pressure (“adiabatic expansion”). Clouds form when excess water vapor condenses into water droplets when the temperature drops to a certain point.

The main reasons for rising air, which lead to its cooling, the formation of clouds and condensation: the first is caused abrupt change wind speed and direction and creating everything the necessary conditions for cloud formation turbulence.

The second is an “orthographic rise” of air when passing over mountains and hills. In this case, there may be various types clouds: cloud cap, mountain fog, vortex, flag-like and lenticular clouds.

When moist air cools to its dew point before reaching the summit, mountain fog appears. Everything is perceived as something that has fallen into such a cloud and clings to the top and windward side.

When the air is fairly dry and cools after rising above the mountain top to the dew point, a cloud cap forms. It seems as if the cloud is hanging motionless over the top of the mountain, even despite the wind. This is not the same cloud, strictly speaking, it constantly forms 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 that is enough to cause a cloud and vortices to form in the moist air currents on the leeward side of the mountain.

The cloud that appeared behind the peak flows with the wind and eventually evaporates. Lenticular wavy clouds often form on the crests of undulating air currents that pass over rough terrain.

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

Convergence.

Inside huge weather systems - “cyclones” (areas low pressure) a rise in air masses can also occur.

When, “fighting” for free space, warm moist masses “converge” (converge) with cold air masses - large ridges of clouds are formed. Lighter and warmer air is displaced upward - denser and colder. Often such a “front” brings prolonged rains and heavy precipitation.

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

Scientists have discovered 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 rise. “Stable” conditions are when with high speed The ambient air temperature drops, but 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.

Classification of clouds.

Clouds, influenced by the many processes involved in their formation, come in 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 classifying clouds into five types and three tiers in 1802. Lamarck believed that clouds form as a result of a number of circumstances (although he did not know exactly which ones), and not by chance.

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

And today these basic terms are also used. The first "international cloud atlas" was published in 1896. At that time, clouds were still considered to be non-evolving, permanent masses. But about the fact that every 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 generally accepted abbreviation.

Soaring in the heights.

TO upper clouds include cirrostratus (Cs), cirrocumulus (Cc) and cirrus (Ci). They consist of ice crystals, are found at altitudes of 6 to 18 km, and are not a source of precipitation falling on the Earth.

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

Mid-level 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 torn plates, and altostratus clouds look like gray-blue solid sheets. Very little precipitation falls from mid-level clouds.

Low clouds (up to 3 km altitude) include stratocumulus (Cs), cumulus (Cu), nimbostratus (Ns), stratus (St) and cumulonimbus (Cb). Cumulus, stratocumulus and stratus are made up of droplets, while nimbostratus and cumulonimbus are made up of a mixture of ice and water.

Stratus and stratocumulus clouds are similar to the gray sheet, but the former are a homogeneous layer, while the latter are more fragmented. They may fall with drizzle or light rain. Nimbostratus clouds look like a dark gray layer; they carry snow or continuous rain.

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

Now, by looking at the sky, you can understand what kind of clouds are there and what weather to expect...

Clouds and determining the weather from them. By the shape of the clouds floating across the sky, you can guess with a fair degree of confidence what weather will prevail during the day.

There are the following types of clouds.

Cirrus

Thin, light, haze-like white clouds, transparent to the sun. They are variable in shape, often appearing in the form of stripes, arcs or veins collected in bunches. At night, these clouds can scatter starlight. Mostly indicate changes in the weather. Combined with low cumulus and subsequent cirrostratus may herald the approach of a cyclone with rain.

Cirrocumulus

They are located lower than the feathery ones. They are visible in the sky as ordered clusters of ragged small clubs or stripes and have a spotted or pockmarked texture. At night, dim stars can be eclipsed. Mainly associated with dry weather. However, if they thicken, become gray and sink lower, we must wait for rain.

Cirrostratus

Milky white thin veil of clouds.

Can mix with cirrus and form parallel stripes on the sky. The sun or moon, shining through these clouds, acquires the hue of a halo. Weather changes expected. As with cirrocumulus, if they dip and thicken, you can expect rain within 24 hours.

Altocumulus

Small flattened, rounded clusters, gray on the underside. They gather in loose, unorganized formations, with blue skies often visible between them. Sometimes they look like rushing groups of clouds, rolling like waves. They can be thick enough to blot out the sun. At dawn and sunset they create colorful patterns in the sky. If the clouds thicken and lower, expect short thundershowers. If the altocumulus clouds are higher up, taking on the shape of towers, the thunderstorm can be even more severe.

Altostratified

A veiny and denser variant of cirrostratus clouds.

They scatter the light of stars and, when particularly dense, can blur the disk of the sun or moon. If they descend, thicken and darken, or if low, gray, ragged clouds form beneath them, heavy and persistent rain or snow is likely to begin within a few hours.

Layered

Very low clouds, similar to fog, but raised above the ground by 150-600 m. They form a continuous layer. Usually foreshadowed rainy weather, especially in combination with strong winds.

Nimbostratus

A homogeneous, dark gray layer of clouds covering sunlight. Typically part of a major low pressure area. Usually brings long, steady rain or snow.

Stratocumulus

Soft, round white clouds collected in orderly layers, lines, waves or elongated puffs. Often gray underneath. Stratocumulus clouds usually dissipate at night, leaving behind good weather.

Cumulus

Classic white, "puffy" clouds with a curled surface, accentuated by shadows, and a dome-shaped top. May be part of an anticyclone bringing clear weather. But if it starts to get dark, then this may portend strong wind and rain.

Cumulonimbus

Cumulus clouds, which have the appearance of mountains, are dark, menacing in color and have a flat base. The forecast is for heavy, heavy rain and thunderstorm conditions are possible.

Sometimes they cover the sky in the form of a continuous veil, sometimes they appear in the form of isolated cloud masses, sometimes developing very powerfully in height, sometimes they have a relatively delicate structure, sometimes in the form of stripes or feathers of a fibrous structure, sometimes in the form of small white lambs, or scales, etc. n. The density of clouds largely depends on their height. The thickest and most powerful clouds usually float at low altitudes - below two kilometers. The higher the clouds float, the thinner and more transparent their structure becomes. All the clouds that we observe in the sky usually float in a layer from the surface to a height of 10-12 kilometers.

Our idea of ​​the weather is usually closely related to the picture of the sky, that is, to the shapes and number of clouds observed in the sky.

Low clouds

Fog

When the process of condensation of water vapor occurs in the lowest layers, the resulting cloud is located near the surface of the earth. It immediately surrounds us and appears to us in the form of fog. In general, any cloud, if you are inside it, for example, on a mountain or when flying on an airplane, appears to the observer in the form of fog.

Stratus clouds

Everyone knows the picture of clouds in gloomy gray weather, when the sky is covered with a continuous, completely homogeneous gray cloud cover, located relatively low above the ground. It gives the impression of a lifted fog. usually does not shine through this veil at all. Sometimes a light drizzle falls from it in the form of fine water dust, and in winter sometimes tiny, rare snowflakes. These are the so-called stratus clouds (international name Stratus or abbreviated St). Essentially, these clouds are fog raised above the surface of the earth. They usually swim not high - sometimes at an altitude of a hundred or several hundred meters, usually not higher than a kilometer.

In some cases, stratus clouds are torn into separate pieces with ragged edges. Then they are called fractostratus clouds (international name Fracto-Stratus or abbreviated as FrSt).

Nimbostratus clouds

Let's remember another picture of the sky. Inclement weather. It's raining, but not the kind that breaks out quickly in the form of a downpour and passes quickly, but rain (snow in winter), which, as they say, “charges for a long time” and over a large area (it is called continuous rain). It may happen that there is no rain yet, but the very appearance of the clouds makes us expect it soon. The clouds have the appearance of a low, dark gray layer, almost uniform, so that only in some places this layer appears darker, but in other places it is a little lighter. These typical clouds inclement weather are called nimbostratus or colloquially rain (international name Nimbo-Stratus or abbreviated NbSt).

Stratocumulus clouds

The latter form of clouds should not be confused with stratocumulus clouds (international name Strato-Cumulus, abbreviated StCu), which appear as stretching dark cloud banks or spherical masses that give the sky a wavy appearance. Typically, the cover of stratocumulus clouds is not continuous, but with gaps between individual shafts. These clouds are usually not accompanied by precipitation. They are most often found in the winter season, although they also occur in the summer. In their form, they are, as it were, transitional from the stratus clouds described above to cumulus, which we will focus on.

Cumulus clouds

Let us now consider the shape of the clouds, usual for good summer day. In the morning the sky is completely clear; but around 8-10 o'clock light, white clouds begin to appear in the sky in some places. They grow quickly both to the sides and mainly upwards. Their base is almost horizontal, while the tops have a dome-shaped appearance with separate, usually sharply defined convexities at the top. Illuminated by the sun, they appear dazzling white to the observer. If they are between the observer and the sun, they appear dark in the middle part.

These clouds grow during the day, but in the evening they usually begin to melt and gradually disappear. They are called cumulus (international name Cumulus, abbreviated Cu).

Thunderclouds

Sometimes clouds, which initially look like cumulus clouds, grow so intensely that they reach huge size(often up to several kilometers), take the form of mountains or huge towers. The very top of the cloud often begins to take on a fibrous structure instead of the shape of bulges, and sometimes looks like an anvil. Such clouds usually bring with them thunderstorms, showers and hail, and in winter heavy snowfalls. They are called cumulonimbus clouds (international name Cumulo-Nimbus, abbreviated CuNb); when they are accompanied by thunderstorms, they are usually called thunderstorms in common parlance.

The five forms of clouds we have considered—stratus, nimbostratus, stratocumulus, cumulus, and cumulonimbus—are called “lower clouds.” They float relatively low above the surface of the earth, so that their base is no higher than 2000 meters. For stratus clouds, the limiting level of the lower base is approximately two times less (they usually float no higher than 1000 meters). Low level clouds differ from other cloud forms (middle and upper levels) described below in their density and power, noticeably shading the sun. In addition, swimming at a relatively low altitude, they often create a certain difficulty when flying. Flight in cumulonimbus clouds is further complicated by the fact that these clouds are often accompanied by vortices and generally restless air movements.

Mid-level clouds

Let us now turn to the consideration of higher clouds, the so-called “middle tier” clouds.

Altostratus clouds

A continuous cloud cover of the sky in the form of a grayish or bluish veil can be located significantly above 1000 meters, that is, above the maximum level at which ordinary stratus clouds float. This veil is usually so transparent that the sun or moon can be seen as a more or less blurry spot. Such cloud cover is called altostratus clouds (international name Alto-Stratus, abbreviated AlSt). Altostratus clouds, becoming denser, can gradually turn into nimbostratus clouds, which have more dark color completely covering the sun or moon. Covered rain or snow sometimes falls from the layer of altostratus clouds.

Altocumulus clouds

These clouds have an international name - Aito-Cumuius, abbreviated as A-Cu. In appearance, they correspond to the cumulus clouds of the lower tier, although they differ from them by much less power, a more delicate structure and float much higher. To the observer, altocumulus clouds appear as winged clouds, sometimes as small flakes of snow, or small rounded flakes of cotton wool, often approaching a spherical shape, with fairly distinct edges, or as scales. Their thickness is so insignificant that they almost do not shade the sun, due to which they appear evenly in the sky white no shadows. These winglets, flakes or scales are usually found on the palate in connected groups or rows. Sometimes they are presented in the form of parallel stripes or waves that seem (due to “perspective”) to converge on each other at the horizon. Altocumulus clouds also belong to the so-called “middle” layer clouds. They usually swim at altitudes between 2000 and 6000 meters.

Upper clouds

The highest forms of clouds, or upper level clouds, include three forms: cirrocumulus, cirrostratus, and cirrus.

Cirrocumulus clouds

These clouds have the international name Cirro-Cumulus, abbreviated CiCu. They're in transitional forms sometimes they resemble in miniature high cumulus clouds, with which they can be confused. To an observer, cirrocumulus clouds appear as very small white flakes or miniature lumps of snow, arranged in regular groups or rows, or as ripples in the sand. Sometimes they form from cirrostratus or cirrus clouds, described below, and have a fibrous structure. They are of such a delicate structure that they do not provide any shadow on their lower side.

Cirrostratus clouds

Similar to stratus clouds in lower tier and altostratus in the middle, in the upper tier there is also a cloud form in the form of a continuous homogeneous veil, the so-called cirrostratus clouds (international name Cirro-Stratus or abbreviated CiSt). These clouds cover the sky with a continuous whitish veil, completely blurred and giving the sky a whitish tint. Through this veil the sun is visible so clearly that the edges of their disks have completely distinct outlines and are not blurred. A characteristic feature Cirrostratus clouds are caused by the appearance of circles in the sky near the sun or moon.

Spindrift clouds

Sometimes very delicate individual clouds of a fibrous or thread-like structure are observed in the sky at high altitudes. They happen the most various shapes, sometimes in the form of feathers or horse tails, sometimes in the form of thin flakes of cotton wool with a fibrous structure, sometimes in the form of threads or light, transparent strokes of white paint on blue sky. Sometimes individual clouds are scattered randomly across the sky, sometimes they are intricately mixed up with each other or arranged in the form of parallel stripes crossing the entire sky or part of it, and, due to perspective, such stripes seem to converge with each other. Such clouds are called cirrus (international name Cirrus or abbreviated Ci).

Cirrus clouds are the highest of the upper level clouds.

In general, upper clouds are usually located at levels above 6,000 meters.

In our latitudes, the upper limit of the layer of air where the highest “cirrus” clouds form extends to approximately 11-12 kilometers. Less often they are observed slightly higher.

The highest clouds

The layer of the atmosphere from the surface of the earth to a height of about 11 kilometers (in our latitudes), called the “troposphere,” is characterized by the fact that it decreases with increasing altitude. In the overlying layer, called the “stratosphere,” the temperature drop with height stops. Thus, all clouds observed in the sky float in the troposphere. In higher layers of the atmosphere, clouds of the usual type are not observed at all.

noctilucent clouds

However, in rare cases, sometimes faintly luminous, so-called “noctilucent clouds” appear at enormous altitudes, the origin of which is still largely mysterious. They are observed in the sky after sunset, when its rays continue to obliquely illuminate the upper layers of the atmosphere in which these clouds float, which is why they seem to glow against the dark background of the sky after sunset.

These clouds were discovered in 1885, shortly after the huge eruption of the Krakatoa volcano (between the islands of Java and Sumatra) in 1883. They floated at an exceptionally high altitude: about 70-80 kilometers. Some scientists have expressed the idea that these clouds are products of a volcanic eruption thrown to enormous heights, consisting mainly of ice crystals formed from water vapor released during the eruption. Reflecting Sun rays, they seem to glow to us. However, in the last century (since 1926), noctilucent clouds began to be observed again in the sky, but at a much lower altitude, namely about 28 kilometers.

Observations of the appearance of noctilucent clouds are important in that they may help resolve the still mysterious question of the reasons for their origin.