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

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

Let us limit ourselves to discussing the formation of clouds caused by a decrease in air temperature during upward movement. Obviously, such a process is significantly different from the formation of fog - after all, the fog practically does not rise upward, it remains directly at the earth's surface.

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

The process of cloud formation begins with the fact that some air mass rises upward. As you rise, the air will expand. This expansion can be considered adiabatic, since the air rises relatively quickly, and therefore, if its volume is sufficiently large (and a really large volume of air is involved in the formation of a cloud), heat exchange between the rising air and environment It just doesn’t have time to happen during the ascent. During adiabatic expansion, air, without receiving heat from the outside, does work only due to its own internal energy, and then cools. So, the air rising will cool.

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

H = 120(T 0 −T R),

Where H measured in meters.

The air that continues to flow from below crosses the condensation level, and the process of steam condensation occurs 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, a vaguely defined upper boundary of the cloud will form. 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 encounter mountains or other natural elevations along its path. Overcoming them, air masses are forced to rise upward. Formed in in this case clouds are called clouds of orographic origin (from Greek wordόρος, meaning "mountain"). It is clear that such clouds do not develop significantly in height (it is limited by the height of the elevation overcome by the air); in this case, stratus and nimbostratus clouds appear.

The third reason for the rise of air masses is the emergence of warm and cold atmospheric fronts. Cloud formation occurs especially intensely over a warm front - when a warm air mass, advancing on a cold air mass, is forced to slide up a wedge of retreating cold air. The frontal surface (the surface of the cold wedge) is very flat - the tangent of its angle of inclination to the horizontal surface is only 0.005–0.01. Therefore, the upward movement of warm air differs little from the horizontal movement; As a result, the cloudiness that appears above the cold wedge develops weakly in height, but has a significant horizontal extent. Such clouds are called ascending clouds. In the lower and middle tiers these are nimbostratus and altostratus clouds, and in the upper tier these are cirrostratus and cirrus (it is clear that the clouds of the upper tier are formed far behind the atmospheric front line). The horizontal extent of ascending 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 lifts it. In this case, along with ascending clouds, cumulus clouds may also appear.

The fourth reason for the rise of air masses is cyclones. Air masses, moving along the surface of the earth, swirl towards the center of the depression in the cyclone. Accumulating there, they create a vertical pressure difference and rush upward. The intense rise of air up to the boundary of the troposphere leads to powerful cloud formation - clouds of cyclonic origin appear. These can be nimbostratus, altostratus, or cumulonimbus clouds. Precipitation falls from all such clouds, creating the 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).

Cumulus clouds- dense, bright white clouds during the day with significant vertical development. Associated with the development of convection in the lower and partially middle troposphere.

Most often, cumulus clouds appear in cold air masses in the rear of a cyclone, but are often observed in warm air masses in cyclones and anticyclones (except for the central part of the latter).

In temperate and high latitudes they are observed mainly in the warm season (the second half of spring, summer and first half of autumn), and in the tropics all year round. As a rule, they appear in the middle of the day and disappear in the evening (although they can also be observed over the seas at night).

Kinds cumulus clouds:

Cumulus clouds are dense and well developed vertically. They have white dome-shaped or cumulus-shaped tops with a flat base that is grayish or bluish in color. The outlines are sharp, but with strong gusty wind edges may become torn.

Cumulus clouds are located in the sky in the form of individual rare or significant accumulations of clouds that cover almost the entire sky. Individual cumulus clouds are usually scattered randomly, but can form ridges and chains. Moreover, their bases are at the same level.

The height of the lower boundary of cumulus clouds strongly depends on the humidity of the surface air and most often ranges from 800 to 1500 m, and in dry air masses (especially in steppes and deserts) it can be 2-3 km, sometimes even 4-4.5 km.

Causes of cloud formation. Condensation level (dew point)

The atmospheric air always contains some amount of water vapor, which is formed as a result of the evaporation of water from the surface of land and ocean. The rate of evaporation depends primarily on temperature and wind. The higher the temperature and the greater the steam capacity, the greater the evaporation.

The air can accept water vapor to a certain extent, until it becomes rich. If saturated air is heated, it will again acquire the ability to accept water vapor, i.e. it will again become unsaturated. As unsaturated air cools, it approaches saturation. Thus, the ability of air to contain more or less water vapor depends on temperature

The amount of water vapor contained in the air at a given moment (in g per 1 m3) is called absolute humidity.

The ratio of the amount of water vapor contained in the air at a given moment to the amount that it can contain at a given temperature is called relative humidity and is measured as a percentage.

The moment of transition of air from an unsaturated state to a saturated state is called dew point(level of condensation). The lower the air temperature, the less water vapor it can contain and the higher the relative humidity. This means that when the air is cold, the dew point reaches the dew point faster.

When the dew point reaches, i.e. when the air is completely saturated with water vapor, when the relative humidity approaches 100%, water vapor condensation– the transition of water from a gaseous state to a liquid state.

When water vapor condenses in the atmosphere at an altitude of several tens to hundreds of meters and even kilometers, clouds.

This occurs as a result of the evaporation of water vapor from the Earth's surface and its lifting by rising currents of warm air. Depending on their temperature, clouds consist of water droplets or ice and snow crystals. These droplets and crystals are so small that they are retained in the atmosphere even by weak rising air currents. Clouds that are supersaturated with water vapor and have a dark purple or almost black tint are called clouds.

Structure of a cumulus cloud crowning an active TVP

Air currents in cumulus clouds

The thermal flow is a column of rising air. The rising warm air is replaced by cold air from above and zones of downward air movement are formed along the edges of the air flow. The stronger the flow, i.e. the faster warm air rises, the faster it is replaced and the faster it descends at the edges cold air.

These processes naturally continue in the clouds. Warm air rises, cools and condenses. Droplets of water, together with cold air from above, fall down, replacing warm air. The result is a vortex movement of air with a strong rise in the center and an equally strong downward movement at the edges.

Formation of thunderclouds. Life cycle of a thundercloud

The necessary conditions for the emergence of a thundercloud are the presence of conditions for the development of convection or another mechanism that creates upward flows, a supply of moisture sufficient for the formation of precipitation, and the presence of a structure in which some of the cloud particles are in a liquid state, and some are in an icy state. There are frontal and local thunderstorms: in the first case, the development of convection is caused by the passage of a front, and in the second, by uneven heating of the underlying surface within one air mass.

You can break the life cycle of a thundercloud into several stages:

• the formation of cumulonimbus clouds and its development due to the instability of the local air mass and convection: the formation of cumulonimbus clouds;
• the maximum phase of development of a cumulonimbus cloud, when the most intense precipitation, squally winds during the passage of a thunderstorm front, and the most severe thunderstorm are observed. This phase is also characterized by intense downward air movements;
• destruction of a thunderstorm (destruction of cumulonimbus clouds), reduction in the intensity of precipitation and thunderstorms until they cease).

So, let's look in more detail at each stage of thunderstorm development.

Cumulus cloud formation

Let’s say that as a result of the passage of a front or intense heating of the underlying surface by the sun’s rays, convection air movement occurs. When the atmosphere is unstable, warm air rises. Rising upward, the air cools adiabatically, reaching a certain temperature at which condensation of the moisture contained in it begins. Clouds begin to form. During condensation, there is a release of thermal energy sufficient for further rise of air. In this case, a cumulus cloud develops vertically. The speed of vertical development can range from 5 to 20 m/s, so the upper limit of the formed cumulonimbus cloud, even in the local air mass, can reach 8 or more kilometers above the earth's surface. Those. within about 7 minutes, a cumulus cloud can grow to altitudes of about 8 km and turn into a cumulonimbus cloud. As soon as a cumulus cloud growing vertically has passed the zero isotherm (freezing temperature) at a certain altitude, ice crystals begin to appear in its composition, although the total number of droplets (already supercooled) dominates. It should be noted that even at temperatures of minus 40 degrees, supercooled drops of water can occur. At the same moment, the process of precipitation formation begins. As soon as precipitation begins to fall from the cloud, the second stage of the evolution of a lightning storm begins.

Maximum phase of thunderstorm development

At this stage, the cumulonimbus cloud has already reached its maximum vertical development, i.e. reached the “locking” layer of more stable air - the tropopause. Therefore, instead of vertical development, the top of the cloud begins to develop in the horizontal direction. A so-called “anvil” appears, which is cirrus clouds consisting of ice crystals. In the cloud itself, convective currents form upward flows of air (from the base to the top of the cloud), and precipitation causes downward flows (directed from the top of the cloud to its base, and then even to the earth’s surface). Precipitation cools the air adjacent to it, sometimes by 10 degrees. The air becomes denser, and its fall to the surface of the earth intensifies and becomes more rapid. At such a moment, usually in the first minutes of a rainstorm, squally winds may be observed near the ground, dangerous for aviation and capable of causing significant destruction. They are sometimes mistakenly called “tornadoes” in the absence of a real tornado. The most intense thunderstorms are observed at this time. Precipitation leads to the predominance of downward air currents in a thundercloud. The third one is coming The final stage evolution of a thunderstorm - destruction of a thunderstorm.

Lightning storm destruction

The ascending air flows in a cumulonimbus cloud are replaced by downward flows, thereby blocking the access of warm and moist air responsible for the vertical development of the cloud. The thundercloud is completely destroyed, and in the sky there remains only an “anvil” consisting of cirrus clouds, which is absolutely unpromising from the point of view of the formation of a thunderstorm.

Dangers associated with flying near cumulus clouds

As mentioned above, clouds are formed due to the condensation of rising warm air. Near the lower edge of cumulus clouds, warm air accelerates because The ambient temperature drops and replacement occurs faster. A hang glider, picking up in this warm air flow, may miss the moment when its horizontal speed is even higher than the ascent speed, and end up being pulled along with the rising air into the cloud.

In a cloud, due to the high concentration of water droplets, visibility is practically zero; accordingly, the hang glider instantly loses orientation in space and can no longer tell where and how he is flying.

In the worst case scenario, if warm air rises very quickly (for example, in a thundercloud), the hang glider can accidentally fall into an adjacent zone of rising and falling air, which will lead to a somersault and, most likely, destruction of the device. Or the pilot will be raised to heights with severe subzero temperatures and thin air.

Analysis and short-term weather forecasting. Atmospheric fronts. External signs of approaching cold and warm fronts

In previous lectures, I talked about the possibility of predicting flying and non-flying weather, the approach of one or another atmospheric front.

I remind you that atmospheric front is a transition zone in the troposphere between adjacent air masses with different physical properties.

When replacing and mixing one mass of air with another with different physical properties - temperature, pressure, humidity - various natural phenomena, which can be used to analyze and predict the movement of these air masses.

So, when a warm front approaches within a day, its harbingers appear - cirrus clouds. They float like feathers at an altitude of 7-10 km. At that time Atmosphere pressure goes down. The arrival of a warm front is usually associated with warming and heavy, drizzling precipitation.

On the contrary, the onset of a cold front is associated with stratocumulus rain clouds, piling up like mountains or towers, and precipitation from them falls in the form of showers with squalls and thunderstorms. The passage of a cold front is associated with colder temperatures and stronger winds.

Cyclones and anticyclones

The earth rotates and moving air masses are also involved in this circular motion, twisting in a spiral. These huge atmospheric eddies are called cyclones and anticyclones.

Cyclone- an atmospheric vortex of huge diameter with reduced air pressure in the center.

Anticyclone– an atmospheric vortex with increased air pressure in the center, with a gradual decrease from the central part to the periphery.

We can also predict the onset of a cyclone or anticyclone based on weather changes. Thus, a cyclone brings with it cloudy weather with rain in the summer and snowfall in the winter. And an anticyclone means clear or partly cloudy weather, calm wind and lack of precipitation. The weather is stable, i.e. it does not change noticeably over time. From the point of view of flights, of course, anticyclones are more interesting to us.

Cold front. Cloud structure in a cold front

Let's return to the fronts again. When we say that a cold front is “coming”, we mean that a large mass of cold air is moving towards warmer air. Cold air is heavier, warm air is lighter, so the advancing cold mass seems to creep under the warm one, pushing it upward. This creates a strong upward air movement.

The rapidly rising warm air cools in the upper layers of the atmosphere and condenses, causing clouds to appear. As I already said, there is a steady upward movement of air, so the clouds, having a constant supply of warm, moist air, grow upward. Those. The cold front brings cumulus, stratocumulus and nimbus clouds with good vertical development.

The cold front moves, the warm front is pushed upward, and the clouds become oversaturated with condensed moisture. At some point, it pours down in showers, as if dumping the excess until the force of the upward movement of warm air again exceeds the gravity of the water drops.

Warm front. Cloud structure in a warm front

Now imagine the opposite picture: warm air moves towards cold air. Warm air is lighter and when moving it creeps onto cold air, atmospheric pressure drops, because. again, the column of lighter air presses less.

As the warm air rises through the cold air, it cools and condenses. Cloudiness appears. But the upward movement of air does not occur: the cold air has already spread below, there is nothing for it to push out, the warm air is already at the top. Because There is no upward movement of air, warm air is cooled evenly. The cloud cover is continuous, without any vertical development - cirrus clouds.

Hazards associated with the advance of cold and warm fronts

As I said earlier, the onset of a cold front is characterized by a powerful upward movement of warm air and, as a result, the redevelopment of cumulus clouds and thunderstorm formation. In addition, a sharp change in the upward movement of warm air and the adjacent downward movement of cold air, trying to replace it, leads to severe turbulence. The pilot feels this as a strong bump with sharp sudden rolls and lowering/raising of the nose of the aircraft.

In the worst case, turbulence can lead to a somersault; in addition, the processes of takeoff and landing of the device are complicated; flying near slopes requires greater concentration.

Frequent and severe thunderstorms can drag in an inattentive or carried away pilot, and a somersault will occur already in the cloud, being thrown to a great height, where it is cold and there is no oxygen - and possible death.

A warm front is unsuitable for good soaring flights and does not pose any danger, except perhaps the danger of getting wet.

Secondary fronts

The division within the same air mass, but between regions of air of different temperatures, is called secondary front. Secondary cold fronts are found near the Earth's surface in pressure troughs (areas low blood pressure) in the rear of the cyclone behind the main front, where the wind converges.

There can be multiple secondary cold fronts, each separating cold air from colder air. The weather on a secondary cold front is similar to the weather on a cold front, but due to smaller temperature contrasts, all weather phenomena are less pronounced, i.e. clouds are less developed, both vertically and horizontally. Precipitation zone, 5-10 km.

In summer, secondary cold fronts are dominated by cumulonimbus clouds with thunderstorms, hail, squalls, strong wind and icing, and in winter there are general snowstorms and snow charges that impair visibility to less than 1 km. The vertical front develops up to 6 km in summer, and up to 1-2 km in winter.

Occlusion fronts

Occlusion fronts are formed as a result of the closure of cold and warm fronts and the displacement of warm air upward. The process of closure occurs in cyclones, where a cold front, moving at high speed, overtakes a warm one. In this case, warm air breaks away from the ground and is pushed upward, and the front near the earth's surface moves, essentially already under the influence of the movement of two cold air masses.

It turns out that three air masses are involved in the formation of the occlusion front - two cold and one warm. If the cold air mass behind the cold front is warmer than the cold mass in front of the front, then it, displacing warm air upward, will simultaneously flow onto the front, colder mass. This front is called warm occlusion(Fig. 1).

Rice. 1. Warm occlusion front on a vertical section and on a weather map.

If the air mass behind the cold front is colder than the air mass in front of the warm front, then this rear mass will flow under both the warm and the front cold air mass. This front is called cold occlusion(Fig. 2).

Rice. 2. Cold occlusion front on a vertical section and on a weather map.

Occlusion fronts go through a number of stages in their development. The most difficult weather conditions on occlusion fronts are observed in starting moment closing of thermal and cold fronts. During this period, the cloud system is a combination of warm and cold front clouds. Precipitation of a blanket nature begins to fall from nimbostratus and cumulonimbus clouds; in the frontal zone they turn into showers.

The wind intensifies before the warm front of the occlusion, weakens after its passage and turns to the right.

Before the cold front of the occlusion, the wind intensifies to a storm, after its passage it weakens and sharply turns to the right. As warm air is displaced into higher layers, the occlusion front gradually blurs, the vertical power of the cloud system decreases, and cloudless spaces appear. Nimbostratus clouds gradually change to stratus, altostratus to altocumulus, and cirrostratus to cirrocumulus. Precipitation stops. The passage of old occlusion fronts is manifested in the influx of altocumulus clouds of 7-10 points.

The conditions for swimming through the zone of the occlusion front in the initial stage of development are almost no different from the conditions for swimming, respectively, when crossing the zone of warm or cold fronts.

Intramass thunderstorms

Thunderstorms are generally classified into two main types: intramass and frontal. The most common thunderstorms are intramass (local) thunderstorms, which occur far from frontal zones and are caused by the characteristics of local air masses.

Intramass thunderstorm is a thunderstorm associated with convection within an air mass.

The duration of such thunderstorms is short and, as a rule, is no more than one hour. Local thunderstorms can be associated with one or more cumulonimbus cloud cells and go through the standard stages of development: cumulonimbus initiation, development into thunderstorm, precipitation, disintegration.

Typically, intramass thunderstorms are associated with a single cell, although multicell intramass thunderstorms also occur. In multicell thunderstorm activity, downward flows of cold air from the “mother” cloud create upward flows that form the “daughter” thundercloud. In this way, a series of cells can form.

Signs of improving weather

1. The air pressure is high, hardly changes or increases slowly.
2. The diurnal variation in temperature is sharply expressed: hot during the day, cool at night.
3. The wind is weak, intensifies in the afternoon, and subsides in the evening.
4. The sky is cloudless all day or covered with cumulus clouds, disappearing in the evening. Relative air humidity decreases during the day and increases at night.
5. During the day the sky is bright blue, twilight is short, the stars twinkle faintly. In the evening the dawn is yellow or orange.
6. Heavy dew or frost at night.
7. Fogs over lowlands, increasing at night and disappearing during the day.
8. At night it is warmer in the forest than in the field.
9. Smoke rises from chimneys and fires.
10. Swallows fly high.

Signs of worsening weather

1. The pressure fluctuates sharply or continuously decreases.
2. The daily variation of temperature is weakly expressed or with a violation of the general variation (for example, at night the temperature rises).
3. The wind intensifies, abruptly changes its direction, the movement of the lower layers of clouds does not coincide with the movement of the upper ones.
4. Cloudiness is increasing. Cirrostratus clouds appear on the western or southwestern side of the horizon and spread throughout the sky. They give way to altostratus and nimbostratus clouds.
5. It's stuffy in the morning. Cumulus clouds grow upward, turning into cumulonimbus - to a thunderstorm.
6. Morning and evening dawns are red.
7. By night the wind does not subside, but intensifies.
8. Light circles (halos) appear around the Sun and Moon in cirrostratus clouds. There are crowns in the middle-tier clouds.
9. There is no morning dew.
10. Swallows fly low. Ants hide in anthills.

Stationary waves

Stationary waves- This is a type of transformation of horizontal air movement into a wave-like one. A wave can occur when fast-moving air masses meet mountain ranges of considerable height. A necessary condition for the occurrence of a wave is the stability of the atmosphere extending to a considerable height.

To see the atmospheric wave pattern, you can walk up to a stream and watch the flow around a submerged rock. Water, flowing around the stone, rises in front of it, creating a semblance of fiberboard. Behind the stone, ripples or a series of waves are formed. These waves can be quite large in a fast and deep stream. Something similar happens in the atmosphere.

When flowing over a mountain range, the speed of the flow increases, and the pressure in it drops. Therefore, the upper layers of air decrease somewhat. Having passed the top, the flow reduces its speed, the pressure in it increases, and some of the air rushes upward. Such an oscillatory pulse can cause a wave-like movement of the flow behind the ridge (Fig. 3).

Rice. 3. Scheme of formation of stationary waves:
1 - undisturbed flow; 2 - downward flow over an obstacle; 3 - lenticular cloud at the top of the wave; 4 - cap cloud; 5 - rotor cloud at the base of the wave

These stationary waves often travel to high altitudes. The evaporation of a glider in a wave flow to a height of more than 15,000 m has been recorded. The vertical wave speed can reach tens of meters per second. The distances between neighboring “bumps” or wavelength range from 2 to 30 km.

The air flow behind the mountain is divided in height into two layers that differ sharply from each other - a turbulent sub-wave layer, whose thickness ranges from several hundred meters to several kilometers, and a laminar wave layer located above it.

It is possible to use wave flows if there is a second sufficiently high ridge in the turbulent zone and at such a distance that the rotor zone from the first does not affect the second ridge. In this case, the pilot, starting from the second ridge, immediately enters the wave zone.

When there is sufficient air humidity, lenticular clouds appear at the tops of the waves. The lower edge of such clouds is located at an altitude of at least 3 km, and their vertical development reaches 2 - 5 km. It is also possible for a cap cloud to form directly above the mountain top and rotor clouds behind it.

Despite the strong wind (a wave can occur at a wind speed of at least 8 m/s), these clouds are motionless relative to the ground. When a certain “particle” of the air flow approaches the top of a mountain or wave, the moisture contained in it condenses and a cloud is formed.

Behind the mountain, the formed fog dissolves, and the stream “particle” becomes transparent again. Above the mountain and at the tops of the waves, the speed of the air flow increases.

At the same time, the air pressure decreases. From the school physics course (gas laws) it is known that with a decrease in pressure and in the absence of heat exchange with the environment, the air temperature decreases.

A decrease in air temperature leads to moisture condensation and the formation of clouds. Behind the mountain the flow slows down, the pressure in it increases, and the temperature rises. The cloud disappears.

Stationary waves can also appear over flat terrain. In this case, the cause of their formation may be a cold front or vortices (rotors) that arise at different speeds and directions of movement of two adjacent layers of air.

Weather in the mountains. Peculiarities of weather changes in the mountains

The mountains are closer to the sun and, accordingly, warm up faster and better. This leads to the formation of strong convection currents and the rapid formation of clouds, including thunderstorms.

In addition, mountains are a significantly rugged part of the earth's surface. The wind, passing over the mountains, is turbulized as a result of bending around many obstacles different sizes- from a meter (stones) to a couple of kilometers (the mountains themselves) - and as a result of mixing of passing air by convection currents.

So, mountainous areas are characterized by strong thermal conditions combined with strong turbulence, strong winds from different directions, and thunderstorm activity.

Analysis of incidents and preconditions related to meteorological conditions

The most classic incident associated with meteorological conditions is the blowing away or independent flying of the apparatus into the rotor zone in the leeward part of the mountain (on a smaller scale - the rotor from an obstacle). The prerequisite for this is that the flow goes beyond the ridge line at a low altitude or simple ignorance of the theory. Flying in a rotor is fraught with, at a minimum, unpleasant bumpiness, and at maximum, a somersault and destruction of the apparatus.

The second striking incident was being pulled into a cloud. The prerequisite for this is the processing of TVP near the edge of the cloud, coupled with absent-mindedness, excessive courage or ignorance of the flight characteristics of one’s aircraft. Leading to loss of visibility and orientation in space, in the worst case – to somersault and being thrown to a height unsuitable for life.

Finally, the third classic accident is “twisting” and falling onto a slope or the ground while planting on a hot day. The prerequisite is to fly with the stick thrown, i.e. without reserve speed for maneuver.

Light, fluffy and airy clouds - they float above our heads every day and make us raise our heads up and admire the bizarre shapes and original figures. Sometimes an amazing-looking rainbow breaks through them, and sometimes in the morning or evening during sunset or sunrise the clouds are illuminated by the sun’s rays, giving them an incredible, spirit-enchanting hue. Scientists have been studying air clouds and other types of clouds for a long time. They gave answers to the questions of what kind of phenomenon this is and what types of clouds there are.

In fact, it is not so easy to give an explanation. Because they consist of ordinary droplets of water, which were lifted up by warm air from the surface of the Earth. The largest amount of water vapor is formed over the oceans (at least 400 thousand cubic kilometers of water evaporate here in one year), on land - four times less.

And since in the upper layers of the atmosphere it is much colder than below, the air there cools down quite quickly, the steam condenses, forming tiny particles of water and ice, as a result of which white clouds appear. It can be argued that each cloud is a kind of moisture generator through which water passes.

Water in the cloud is in gaseous, liquid and solid states. Water in the cloud and the presence of ice particles in them affect appearance clouds, its formation, as well as the nature of precipitation. It is the type of cloud that determines the water in the cloud; for example, in shower clouds there is greatest number water, and for nimbostratus this figure is 3 times less. Water in a cloud is also characterized by the amount that is stored in them - the cloud's water reserve (water or ice contained in a cloud column).

But everything is not so simple, because in order for a cloud to form, droplets need condensation grains - tiny particles of dust, smoke or salt (if we are talking about the sea), to which they must stick and around which they must form. This means that even if the air composition is completely supersaturated with water vapor, without dust it will not be able to turn into a cloud.

What exact shape the droplets (water) will take depends primarily on temperature indicators in the upper layers of the atmosphere:

• if the atmospheric air temperature exceeds -10°C, white clouds will consist of water droplets;
• if the temperature of the atmosphere begins to fluctuate between -10°C and -15°C, then the composition of the clouds will be mixed (drip + crystalline);
• if the temperature in the atmosphere is below -15°C, the white clouds will contain ice crystals.

After appropriate transformations, it turns out that 1 cm3 of cloud contains about 200 drops, and their radius will be from 1 to 50 μm (average values ​​are from 1 to 10 μm).

Cloud classification

Everyone has probably wondered what types of clouds are there? Typically, cloud formation occurs in the troposphere, the upper limit of which in polar latitudes is 10 km away, in temperate latitudes - 12 km, in tropical latitudes - 18 km. Other species can often be observed. For example, pearlescent ones are usually located at an altitude of 20 to 25 km, and silver ones - from 70 to 80 km.

Basically, we have the opportunity to observe tropospheric clouds, which are divided into the following types of clouds: upper, middle and lower tiers, as well as vertical development. Almost all of them (except for the last type) appear when moist, warm air rises to the top.

If the air masses of the troposphere are in a calm state, cirrus, stratus clouds (cirostratus, altostratus and nimbostratus) are formed and if the air in the troposphere moves in waves, cumulus clouds appear (cirocumulus, altocumulus and stratocumulus).

Upper clouds

We are talking about cirrus, cirrocumulus and cirrostratus clouds. Sky clouds look like feathers, waves or a veil. All of them are translucent and more or less freely transmit the sun's rays. They can be either extremely thin or quite dense (cirrostratus), which means it is harder for light to get through them. Cloud weather signals the approach of a heat front.

Cirrus clouds can also occur above the clouds. They are arranged in stripes that cross the vault of heaven. In the atmosphere they are located above the clouds. As a rule, sediment does not fall out of them.

In middle latitudes, white upper-level clouds are usually located at an altitude of 6 to 13 km, in tropical latitudes they are located much higher (18 km). In this case, the thickness of the clouds can range from several hundred meters to hundreds of kilometers, which can be located above the clouds.

The movement of upper-tier clouds across the sky primarily depends on wind speed, so it can vary from 10 to 200 km/h. The sky of the cloud consists of small ice crystals, but the weather of the clouds does not provide practical precipitation (and if it does, there is no way to measure them at the moment).

Mid-level clouds (from 2 to 6 km)

These are cumulus clouds and stratus clouds. In temperate and polar latitudes they are located at a distance of 2 to 7 km above the Earth; in tropical latitudes they can rise a little higher - up to 8 km. All of them have a mixed structure and consist of water droplets mixed with ice crystals. Since the height is small, in the warm season they mainly consist of water droplets, in the cold season - of ice droplets. True, precipitation from them does not reach the surface of our planet - it evaporates on the way.

Cumulus clouds are slightly transparent and are located above the clouds. The color of the clouds is white or gray, darkened in places, looking like layers or parallel rows of rounded masses, shafts or huge flakes. Hazy or wavy stratus clouds are a veil that gradually obscures the skies.

They are formed mainly when a cold front pushes a warm one upward. And, although precipitation does not reach the ground, the appearance of middle-tier clouds almost always (except, perhaps, tower-shaped ones) signals a change in the weather for the worse (for example, a thunderstorm or snowfall). This happens due to the fact that cold air itself is much heavier than warm air and moving along the surface of our planet, it very quickly displaces heated air masses upward - therefore, because of this, with a sharp vertical rise of warm air, white clouds of the middle tier are formed first, and then the rain clouds, the sky of which carries thunder and lightning.

Low clouds (up to 2 km)

Stratus clouds, nimbus clouds, and cumulus clouds contain water droplets that freeze into snow and ice particles during the cold season. They are located quite low - at a distance of 0.05 to 2 km and are a dense, uniform low-overhanging cover, rarely located above clouds (other types). The color of the clouds is gray. Stratus clouds look like large shafts. Cloudy weather is often accompanied by precipitation (light rain, snow, fog).

Clouds of vertical development (conventions)

Cumulus clouds themselves are quite dense. The shape is a bit like a dome or tower with rounded outlines. Cumulus clouds can become torn in gusty winds. They are located at a distance of 800 meters from the earth's surface and above, the thickness ranges from 1 to 5 km. Some of them are capable of transforming into cumulonimbus clouds and located above the clouds.

Cumulonimbus clouds can be found at fairly high altitudes (up to 14 km). Their lower levels contain water, the upper levels contain ice crystals. Their appearance is always accompanied by showers, thunderstorms, and in some cases, hail.

Cumulus and cumulonimbus, unlike other clouds, are formed only with a very rapid vertical rise of moist air:

1. Moist warm air rises extremely intensely.
2. At the top, droplets of water freeze, top part the clouds become heavier, descend and stretch towards the wind.
3. A quarter of an hour later a thunderstorm begins.

Upper atmosphere clouds

Sometimes in the sky you can observe clouds that are located in the upper layers of the atmosphere. For example, at an altitude of 20 to 30 km, pearlescent sky clouds form, which consist mainly of ice crystals. And before sunset or sunrise, you can often see silvery clouds, which are located in the upper layers of the atmosphere, at a distance of about 80 km (interestingly, these celestial clouds were discovered only in the 19th century).

Clouds in this category can be located above the clouds. For example, a cap cloud is a small, horizontal, and highly stratus cloud that is often found above clouds such as cumulonimbus and cumulus. This type of cloud can form above an ash cloud or fire cloud during volcanic eruptions.

How long do clouds live?

The life of clouds directly depends on the humidity of the air in the atmosphere. If there is little of it, they evaporate quite quickly (for example, there are white clouds that last no more than 10-15 minutes). If there is a lot, they can last quite a while long time, wait for certain conditions to form, and fall to Earth in the form of precipitation.

No matter how long a cloud lives, it is never in an unchanged state. The particles that make it up constantly evaporate and reappear. Even if outwardly the cloud does not change its height, in fact it is in constant motion, since the drops in it descend, pass into the air under the cloud and evaporate.

Cloud at home

White clouds are fairly easy to make at home. For example, one Dutch artist learned to create it in his apartment. To do this, at a certain temperature, level of humidity and lighting, he released a little steam from the smoke machine. The cloud that turns out is able to last for several minutes, which will be quite enough to photograph an amazing phenomenon.

Clouds can be classified as follows: stratus, cumulus and cirrus. Stratus clouds are observed when a wide band of air slowly rises above the surface of a warm front.

Cumulus clouds form when warm air is released by the soil or when the upper layers of the atmosphere are unstable due to cold air. Cirrus clouds, on the contrary, appear when ice crystals accumulated in the upper atmosphere fall down and are carried by local air currents. These three main varieties often combine to form a long line of additional cloud types.

Cumulus clouds slowly grow as air currents continue to rise. If their growth continues long enough, they can turn into cumulonimbus clouds.

The inversion layer flattens the cloud

If a temperature inversion layer (in which temperature increases with height) forms above a developing cloud, then the cloud may begin to grow horizontally (at the bottom), becoming stratocumulus. If the cloud expands under the influence of the stratosphere, it turns into a flat cumulonimbus. Growing upward or inward Clouds also differ depending on the height of their position above the Earth: lower, middle and upper. Top clouds (found at 5-8 km altitude) include cirrus, cirrostratus and cirrocumulus clouds. Medium clouds, which include altostratus, altocumulus and nimbostratus clouds, are located at altitudes from 2 to 7.3 km. Finally, clouds that form below 2 km altitude are called base clouds; These include stratus and stratocumulus. Vertical clouds that form when air is heated by the sun in close proximity to the surface are cumulus and nimbus.

Curving clouds

Ice crystals from high-altitude cirrus clouds (right) can fall vertically if the speed of the air streams is the same at all altitudes. However, if there is a difference in speed, they may bend or cut.

Altocumulus clouds (below), which form between layers of warm and cold, lower and upper air, respectively, sometimes take on a round shape. They are held between the downward air flows of the upper layer and the upward flows of the lower layer.

Altocumulus clouds

Stratus clouds and rain

When raindrops fall on particularly warm areas of the earth's surface, some of them begin to evaporate as they fall (below). If evaporation continues, the air may become saturated and form stratus clouds.

Clouds forming in waves

When horizontal air masses (below) move quickly in the upper atmosphere and slowly closer to the surface, their rotation creates wave-shaped clouds.

Wave crests

Wave clouds (right) can also be seen at the tops of air currents that move between a dry, warm layer above and a moist, cool layer below.

This article lists and describes all types of clouds.

Cloud types

Upper clouds are formed in temperate latitudes above 5 km, in polar latitudes above 3 km, in tropical latitudes above 6 km. The temperature at this altitude is quite low, so they consist mainly of ice crystals. The upper level clouds are usually thin and white. The most common forms of upper clouds are cirrus and cirrostratus, which can usually be seen in good weather.

Mid-level clouds usually located at an altitude of 2-7 km in temperate latitudes, 2-4 km in polar latitudes and 2-8 km in tropical latitudes. They consist mainly of small particles of water, but at low temperatures they can also contain ice crystals. The most common types of mid-level clouds are altocumulus (altocumulus), altostratus (altostratus). They may have shadowed parts, which distinguishes them from cirrocumulus clouds. This type of cloud usually occurs as a result of air convection, as well as the gradual rise of air ahead of a cold front.

Low clouds They are located at altitudes below 2 km, where the temperature is quite high, so they consist mainly of water droplets. Only in the cold season. When the surface temperature is low, they contain particles of ice (hail) or snow. The most common types of low clouds are nimbostratus and stratocumulus - dark low clouds accompanied by moderate precipitation.

Fig1. Main types of clouds: Cirrus, Ci, Cirrocumulus, Cc, Cirrostratus, Cs, Altocumulus, Ac, Altostratus, As, Altostratus translucidus , As trans) , Stratostratus (Nimbostratus, Ns), Stratus (Stratus, St), Stratocumulus (Stratocumulus, Sc), Cumulus (Cumulus, Cu), Cumulonimbus (Cb)

Pinnate (Cirrus, Ci)

They consist of individual feather-like elements in the form of thin white threads or white (or mostly white) tufts and elongated ridges. They have a fibrous structure and/or a silky sheen. They are observed in the upper troposphere; in mid-latitudes their bases most often lie at altitudes of 6-8 km, in tropical latitudes from 6 to 18 km, in polar latitudes from 3 to 8 km). Visibility inside the cloud is 150-500 m. Constructed from ice crystals large enough to have a noticeable fall speed; therefore, they have a significant vertical extent (from hundreds of meters to several kilometers). However, wind shear and differences in crystal size cause the filaments of cirrus clouds to become skewed and twisted. These clouds are characteristic of the leading edge of a cloud system of a warm front or an occlusion front associated with upslip. They often also develop in anticyclonic conditions and are sometimes parts or remnants of ice caps (anvils) of cumulonimbus clouds.

There are different types: filiform(Cirrus fibratus, Ci fibr.), claw-shaped(Cirrus uncinus, Ci unc.), tower-shaped(Cirrus castellanus, Ci cast.), dense(Cirrus spissatus, Ci spiss.), flaky(Cirrus floccus, Ci fl.) and varieties: confused(Cirrus intortus, Ci int.), radial(Cirrus radiatus, Ci rad.), ridge-shaped(Cirrus vertebratus, Ci vert.), double(Cirrus duplicatus, Ci dupl.).

Sometimes this type of cloud, along with the described clouds, also includes cirrostratus And cirrocumulus clouds.

Cirrocumulus (Cc)

They are often called "lamb". Very high small spherical clouds, elongated in lines. They look like the backs of mackerels or ripples on the coastal sand. The height of the lower boundary is 6-8 km, the vertical length is up to 1 km, visibility inside is 5509-10000 m. They are a sign of an increase in temperature. Often observed together with cirrus or cirrostratus clouds. They are often the precursors of a storm. With these clouds, the so-called “iridization” is the rainbow coloring of the edges of the clouds.

Cirrostratus, Cs)

Halo formed on cirrus clouds

Sail-like clouds of the upper tier, consisting of ice crystals. They look like a homogeneous, whitish veil. The height of the lower edge is 6-8 km, the vertical extent ranges from several hundred meters to several kilometers (2-6 or more), visibility inside the cloud is 50-200 m. Cirrostratus clouds are relatively transparent, so the sun or moon can be clearly visible through them. These upper-level clouds usually form when large layers of air rise upward due to multi-level convergence.

Cirrostratus clouds are characterized by the fact that they often produce halo phenomena around the sun or moon. Halos are the result of the refraction of light by the ice crystals that make up the cloud. Cirrostratus clouds, however, tend to thicken as a warm front approaches, which means increased ice crystal formation. As a result, the halo gradually disappears and the sun (or moon) becomes less visible.

Altocumulus (Ac)

Formation of altocumulus clouds.

Altocumulus (Ac) - typical cloudiness for the warm season. Gray, white, or bluish clouds in the form of waves and ridges, consisting of flakes and plates separated by gaps. The height of the lower boundary is 2-6 km, the vertical length is up to several hundred meters, visibility inside the cloud is 50-80 m. They are usually located above places facing the sun. Sometimes they reach the stage of powerful cumulus clouds. Altocumulus clouds usually occur as a result of rising warm air masses, as well as the arrival of a cold front that pushes warm air upward. Therefore, the presence of altocumulus clouds on a warm and humid summer morning foreshadows the imminent appearance of thunderclouds or a change in weather.

High-stratified (Altostratus, As)

Altostratus clouds

They look like a uniform or faintly wavy veil of gray or bluish color; the sun and moon usually shine through, but faintly. The height of the lower boundary is 3-5 km, the vertical extent is 1-4 km, visibility in the clouds is 25-40 m. These clouds consist of ice crystals, supercooled water droplets and snowflakes. Altostratus clouds may bring heavy rain or snow.

High-layered translucent (Altostratus translucidus, As trans)

Altostratus clouds at sunset

Altostratus translucent clouds. The wavy structure of the cloud is noticeable, the solar circle of the sun is quite visible. Quite visible shadows can sometimes appear on the ground. The stripes are clearly visible. A veil of clouds, as a rule, gradually covers the entire sky. The height of the base is within 3-5 km, the thickness of the As trans cloud layer is on average about 1 km, occasionally up to 2 km. Precipitation falls, but in low and middle latitudes in summer it rarely reaches the ground.

Nimbostratus (Nimbostratus, Ns)

Nimbostratus clouds and strong air currents.

Nimbostratus clouds are dark gray, in the form of a continuous layer. During precipitation, it appears homogeneous; in the intervals between precipitation, some heterogeneity and even some undulation of the layer is noticeable. From stratus clouds They are distinguished by a darker and bluish color, heterogeneity of structure and the presence of dense sediments. The height of the lower boundary is 0.1-1 km, the thickness is up to several kilometers.

Layered (Stratus, St)

Stratus clouds.

Stratus clouds form a homogeneous layer, similar to fog, but located at an altitude of hundreds or even tens of meters. They usually cover the entire sky, but can sometimes appear as broken cloud masses. The base of these clouds can drop very low; sometimes they merge with ground fog. Their thickness is small - tens and hundreds of meters.

Stratocumulus (Stratocumulus, Sc)

Gray clouds consisting of large ridges, waves, plates, separated by gaps or merging into a continuous gray wavy cover. They consist mainly of water droplets. The thickness of the layer is from 200 to 800 m. The sun and moon can only be seen through the thin edges of the clouds. Precipitation, as a rule, does not fall. Light, short-lived precipitation may fall from non-translucent stratocumulus clouds.

Cumulus clouds (Cumulus, Cu)

Cumulus clouds. View from above.

Cumulus clouds are dense, bright white clouds during the day with significant vertical development (up to 5 km or more). The upper parts of cumulus clouds look like domes or towers with rounded outlines. Typically, cumulus clouds arise as convection clouds in cold air masses.

Cumulonimbus (Cb)

Cumulonimbus clouds (Cumulonimbus capillatus incus)

Cumulonimbus - powerful and dense clouds with strong vertical development (up to a height of 14 km), producing heavy rainfall with powerful hail and thunderstorm phenomena. Cumulonimbus clouds/clouds develop from powerful cumulus clouds. They can form a line called a squall line. The lower levels of cumulonimbus clouds consist mainly of water droplets, while at higher levels high levels, where temperatures are well below 0 °C, ice crystals predominate.