Clouds form the lowest in the troposphere. Why do clouds form? Geography. Modern Illustrated Encyclopedia

Droplets of water or ice crystals located at a considerable height above the earth's surface. The formation of clouds occurs as follows: air heated from the Earth expands, becomes light and rises. It is known that it decreases with height, so the rising air gradually cools, and the water from the vapor state passes into the liquid state, forming an accumulation of water droplets. The reason for cloud formation is also the forced rise of water saturated on mountain barriers, while the air rising along the mountain slope meets with increasingly cold layers of the atmosphere. The water vapor turns into water droplets and clouds form. Most often, the formation of clouds is associated with the onset of warm or cold weather.

Depending on the predominance of certain elements, clouds are divided into water, ice, mixed. Water clouds consist of very small droplets with a diameter of 0.01 mm - 0.001 mm. There are several hundred of them in 1 cm3 of a water cloud. Ice clouds are made up of ice crystals. Such clouds usually form over a very high altitude where the air temperature is below 0°C. Mixed clouds contain simultaneously supercooled water droplets of different sizes and ice crystals. There is no sharp boundary between the location of liquid and solid elements in the cloud, since there are powerful transitional layers.

The clouds have different shape, which depends on the conditions of their formation, height, . By international agreement clouds according to the shape of the cluster are divided into 10 genera.

This is the degree of cloud cover in the sky. Evaluate it on a 10-point scale or in%. The height and speed of clouds are measured by a special device - a nefoscope. Based on the analysis of the clouds, it is possible to determine the upcoming one: the appearance of cirrus and then stratus clouds in the sky portends rain; when the clouds increase, thicken, descend, move rapidly, becoming heavier and lowering, cloudy, inclement weather must be expected.

In winter and at night, clouds prevent the temperature from dropping earth's surface and the ground layer of air, as they prevent the outflow of heat from lower layers atmosphere, and in summer and during the day, clouds weaken the heating of the earth's surface, since water drops in them, like lenses, reflect part of the sun's rays. The clouds soften

Clouds fly across the sky, high above our heads. They often attract the attention of adults and children. There is nothing surprising in the fact that you may have many questions about how clouds appear, what they are made of, how they float in the sky, what they are, etc. In this article, you will get answers to all these questions and be able to satisfy your curiosity.

What are clouds made of?

Clouds are made up of many tiny water droplets or ice crystals floating in the sky at different heights.

How are clouds formed?

As the sun heats the water, it turns into a gas called water vapour. This process is called evaporation. As water vapor rises towards the sky, it cools. The higher, the cooler the air. Eventually, the vapor becomes cool enough to condense into water droplets, forming the clouds we see in the sky.

How do clouds float across the sky?

Clouds are lighter than the surrounding air. This means that they can literally float across the sky. At the same time, air flows can increase their speed.

When the clouds accumulate a lot of moisture and become heavy, it starts to rain, hail or snow.

Where do clouds meet?

Diagram of the main layers of the Earth's atmosphere

All major cloud types float in the troposphere; it is the lowest part closest to the earth. Above the troposphere is the stratosphere, and above are the mesosphere, thermosphere, and exosphere.

Why are clouds different?

There are 10 main types of clouds:

Cumulus clouds

They look like fluffy cotton balls. As a rule, cumulus clouds occur on calm, clear days and indicate good weather. However, under certain conditions, they can become thunderstorms.

stratus clouds

These are flat, grey, featureless layers that are often close to the Earth's surface, hiding the clouds above. Sometimes they can cause light rain. Fog is simply a stratus cloud that has descended to ground level. And when you walk in foggy weather, you are actually walking through the clouds.

Stratocumulus clouds

Stratus clouds can break up to form cumulus clouds. Or several cumulus clouds are able to join together, forming layers. The distance between them characterizes this type as stratocumulus clouds.

Altostratus clouds

Altostratus clouds are found in the middle of the troposphere. They are usually thinner and lighter than layered ones. If you look closely at the sky, you can see the sun's rays through such a cloud.

Altocumulus clouds

Like Altostratus, Altocumulus clouds are found in the middle of the troposphere. However, there is a difference, altocumulus clouds are much smaller than cumulus clouds and consist of both ice crystals and water droplets.

Spindrift clouds

Cirrus clouds are the clouds of the high level composed entirely of ice crystals. These are thin clouds that look like a horse's tail.

cirrocumulus clouds

These are cumulus clouds at cirrus altitude. Cirrocumulus clouds are made up entirely of ice crystals. They are like small fish scales in the sky.

Cirrostratus clouds

Cirrostratus clouds are high in the sky. They can cause beautiful optical phenomena such as halo. The sun still shines brightly through these layers, even though the sky may be completely covered in them.

Nimbostratus clouds

Nimbostratus clouds produce prolonged rain or snow, which can be light to moderate. These tall stratus clouds exist at the low and middle levels of the troposphere.

Cumulonimbus clouds

Also known as "cloud kings", cumulonimbus clouds are responsible for very heavy rain and hail. Precipitation falls in a short period of time.

They are also the only clouds that can generate lightning and thunder. Cumulonimbus clouds are very high and often spread over different layers of the sky.

How to distinguish between cumulus, altocumulus and cirrocumulus clouds in the sky?

You can distinguish between these types of clouds with your hand. Extend your hand towards the cloud and close your fingers into a fist. If the cloud is larger than a fist, it is a cumulus cloud.

If the cloud is smaller than a fist, move it aside thumb. When the cloud is larger than a finger, it is altocumulus, and if it is smaller, it is most likely cirrocumulus.

Why are clouds white?

Clouds are white because the droplets inside them are larger than the particles around them. This makes the cloud droplets able to scatter and break the light into different colors, which then combine to form white.

Clouds look gray when they are thick enough to block out sunlight.

What is an airplane contrail?

A contrail forms when planes pass through cool air. The release of warm humid air from the exhaust pipe of the aircraft causes a cloud trail in its path.

How to determine weather by clouds?

It is difficult to accurately predict the weather using clouds, but there are some indications that it can be done! If the clouds are high, dark and cover the entire sky, it will rain for a long time. When most of the sky is blue, you can expect some rain.

If the cumulus clouds get higher and higher, you may experience heavy showers in the evening or even thunder and lightning. However, this often happens on hot and humid days.

I remember how as a child, looking at the clouds in the sky, I always fantasized different figures for myself. It seemed to me that one cloud looked like a bear, and the other like an apple. At that time, I had no idea what a cloud is, how and from what it is formed. Now, together with my daughter, I also like to watch floating clouds, but now, of course, I know much more about them. I am happy to share this information with you.

Where do clouds appear in the sky?

Air contains water vapor. When the temperature rises, it can hold a lot of water vapor, but when the temperature drops, it becomes more and more difficult to retain moisture. At this time, her excess are released from the air in the form of very fine water droplets. Such a process occurs when the thermometer rises above 0. If it is minus outside the window, then from the air ice crystals are released.

In other words, a substance, in this case water, changes from a gas state to a liquid state. This process is called condensation. So, if air condensation has occurred near the earth's surface, then we will observe fog. But if high from the ground, then clouds form at this moment. All this is due to a decrease in air temperature at altitude. In other words, clouds are accumulations of water droplets or ice crystals in the troposphere.

What are the clouds

I think, looking up at the sky, many paid attention to the fact that the clouds are all different. So there are different classifications of clouds. I'll tell you what they are depending on height location. So, they are divided into clouds:

• upper tier;
• middle tier;
• lower tier;
• clouds of vertical development.

Upper clouds soar at an altitude of 6 km from the earth's surface. mid-tier clouds meet at an altitude of 2 to 6 km. They are much larger in size than the clouds from the first group. They are very dense, so you can see the shadow of such a cloud on the ground. Lower clouds float across the sky at an altitude of up to 2 km. They are dark in color, it is these clouds that are the messengers of precipitation. The bases of vertical clouds are at a height of about 2 km, and the rest of it rises up and can reach 6-8 km.

The clouds are actually quite high, and when you look up into the sky, it seems that they seem to be floating overhead and you can easily touch them.

L. Tarasov

Like fogs, clouds are formed by the condensation of water vapor into liquid and solid states. Condensation occurs either as a result of an increase in the absolute humidity of the air, or as a result of a decrease in air temperature. In practice, both factors are involved in cloud formation.

Formation of clouds as a result of convection.

Cloud formation over warm atmospheric front.

Cloud formation over a cold atmospheric front.

The decrease in air temperature is due, firstly, to the rise (ascending movement) of air masses and, secondly, to the advection of air masses - their movement in a horizontal direction, due to which warm air can be above the cold earth's surface.

We confine ourselves to discussing the formation of clouds caused by a decrease in air temperature during an upward movement. It is obvious that such a process differs significantly from the formation of fog - after all, the fog practically does not rise up, it remains directly at the earth's surface.

What makes air rise up? There are four reasons for the upward movement of air masses. The first reason is the convection of air in the atmosphere. On a hot day, the sun's rays strongly warm the earth's surface, it transfers heat to the ground air masses - and their rise begins. Cumulus and cumulonimbus clouds are most often of convective origin.

The process of cloud formation begins with the fact that some air mass rises. As you rise, the air will expand. This expansion can be considered adiabatic, since the air rises relatively quickly, and therefore, with a sufficiently large volume (and a really large volume of air is involved in the formation of a cloud), the heat exchange between the rising air and environment simply does not have time to occur during the ascent. With adiabatic expansion, air, without receiving heat from the outside, does work only due to its own internal energy and then cools down. So, the air rising up will be cooled.

When the initial temperature T 0 of the rising air drops to the dew point T p, corresponding to the elasticity of the vapor contained in it, the process of condensation of this vapor will become possible. In the presence of condensation nuclei in the atmosphere (and they are almost always present), this process really begins. The height H, at which vapor condensation begins, determines the lower boundary of the forming cloud. It is called the level of condensation. In meteorology, an approximate formula for the height H is used (the so-called Ferrel formula):

H \u003d 120 (T 0 -T p),

where H is measured in meters.

The air that continues to flow from below crosses the condensation level, and the process of steam condensation occurs already above this level - the cloud begins to develop in height. The vertical development of the cloud will stop when the air, having cooled, stops rising. In this case, an indistinctly expressed upper bound clouds. It is called the level of free convection. It is located slightly above the level at which the temperature of the rising air becomes equal to the temperature of the surrounding air.

The second reason for the rise of air masses is due to the terrain. The wind blowing along the earth's surface may meet mountains or other natural elevations on its way. Overcoming them, the air masses are forced to rise up. The clouds formed in this case are called clouds of orographic origin (from Greek word oros meaning "mountain"). It is clear that such clouds do not receive a significant development in height (it is limited by the height of the elevation overcome by the air); in this case, stratus and nimbostratus clouds arise.

The third reason for the rise of air masses is the occurrence of warm and cold atmospheric fronts. Cloud formation is particularly intense over warm front- when a warm air mass, advancing on a cold air mass, is forced to slide up the wedge of receding cold air. The frontal surface (the surface of the cold wedge) is very gentle - the tangent of its inclination to the horizontal surface is only 0.005-0.01. So the upward movement warm air differs little from horizontal movement; as a consequence, the cloudiness that arises above the cold wedge develops weakly in height, but has a significant horizontal extent. Such clouds are called upslip clouds. In the lower and middle tiers, these are nimbostratus and altostratus clouds, and in the upper tier - cirrostratus and cirrus (it is clear that the clouds of the upper tier are already formed far behind the atmospheric front line). The horizontal extent of upward slip clouds can be measured in hundreds of kilometers.

Cloud formation also occurs above a cold atmospheric front - when an advancing cold air mass moves under a mass of warm air and thereby raises it. In this case, cumulus clouds may also form in addition to upslip clouds.

The fourth reason for the rise of air masses is cyclones. air masses, moving along the surface of the earth, twist towards the center of the depression in the cyclone. Accumulating there, they create a pressure drop along the vertical and rush upward. Intense rise of air up to the border of the troposphere leads to powerful cloud formation - clouds of cyclonic origin appear. It can be stratified-nimbus, altostratus, cumulonimbus clouds. Precipitation falls from all such clouds, creating rainy weather characteristic of a cyclone.

Based on the book by L. V. Tarasov "Winds and thunderstorms in the Earth's atmosphere." - Dolgoprudny:Publishing House "Intellect", 2011.
Information about the books of the publishing house "Intellect" - on the website

Everyone has seen clouds. They are large and small, almost transparent and very thick, white or dark, pre-stormy. Taking various forms, they resemble animals and objects. But why do they look like that? We will talk about this below.

What is a cloud

Anyone who has flown in an airplane has probably "passed" through the cloud and noticed that it looks like fog, only it is not directly above the ground, but high in the sky. The comparison is quite logical, because both of them are ordinary steam. And it, in turn, consists of microscopic droplets of water. Where do they come from?

This water rises into the air as a result of evaporation from the surface of the earth and water bodies. That's why largest cluster clouds observed over the seas. During the year, about 400 thousand cubic kilometers evaporate from their surface, which is 4 times higher than that of land.

What are there? It all depends on the state of the water that forms them. It can be gaseous, liquid or solid. It may seem surprising, but some clouds are actually made of ice.

We have already found out that clouds are formed as a result of accumulation a large number particles of water. But to complete the process, a link is needed, to which the drops will "stick" and come together. Often this role is played by dust, smoke or salt.

Classification

The height of the location largely determines what clouds are formed from and how they will look. As a rule, the white masses that we are used to seeing in the sky appear in the troposphere. Its upper limit varies depending on geographical location. The closer an area is to the equator, the higher standard clouds can form. For example, over an area with tropical climate the boundary of the troposphere is located at an altitude of about 18 km, and beyond the Arctic Circle - 10 km.

Cloud formation is also possible high altitudes, but they are currently little studied. For example, mother-of-pearl appear in the stratosphere, and silver ones appear in the mesosphere.

Clouds of the troposphere are conditionally divided into types depending on the height at which they are located - in the upper, middle or lower tiers of the troposphere. Air movement also has big influence for cloud formation. In a calm environment, cirrus and stratus clouds form, but if the tropospheres move unevenly, cumulus clouds are more likely to appear.

Upper tier

This gap covers the area of ​​the sky at an altitude of more than 6 km and up to the edge of the troposphere. Considering that the air temperature here does not rise above 0 degrees, it is easy to guess what clouds form in the upper tier. It can only be ice.

By appearance clouds located here are divided into 3 types:

1. Cirrus. They have a wavy structure and can look like individual threads, stripes or whole ridges.
2. cirrocumulus consist of small balls, curls or flakes.
3. Cirrostratus are a translucent likeness of a fabric that "covers" the sky. Clouds of this type can stretch over the entire sky or occupy only a small area.

The height of a cloud located in the upper tier can vary greatly depending on various factors. It can be several hundred meters or tens of kilometers.

Middle and lower tier

The middle tier is a part of the troposphere, usually located between 2 and 6 km. Here there are altocumulus clouds, which are three-dimensional gray or white masses. They consist of water in the warm season and, accordingly, of ice in the cold. The second type of clouds are altostratus. They have and often completely cover the sky. Such clouds carry precipitation in the form of drizzle or light snow, but they rarely reach the surface of the earth.

The lower tier represents the sky directly above us. Clouds here can be of 4 types:

1. Stratocumulus in the form of blocks or shafts of gray color. Can carry precipitation, except when the temperature is too low.
2. layered. They are located below all the others, have a gray color.
3. Layered rain. As you can understand by the name, they carry precipitation, and, as a rule, they are of a continuous nature. These are gray clouds that do not have a specific shape.
4. Cumulus. One of the most recognizable clouds. They look like powerful heaps and clubs with an almost flat base. Such clouds do not bring precipitation.

There is another species that is not included in common list. These are cumulonimbus clouds. They develop vertically and are present in each of the three tiers. Such clouds bring showers, thunderstorms and hail, so they are often called thunderclouds or showers.

Cloud Lifespan

For those who know what clouds form from, the question of their lifespan may also be of interest. Here great importance plays the humidity level. It is a kind of source of vitality for the clouds. If the air in the troposphere is dry enough, then the cloud cannot survive for long. If the humidity is high, it may hover in the sky longer until it becomes more powerful in order to produce precipitation.

As for the shape of the cloud, its life span is very short. Water particles tend to constantly move, evaporate and reappear. Therefore, the same cloud shape cannot be preserved even for 5 minutes.