Purpose of the lesson: learn the classification of clouds and master the skills of determining the type of clouds using the "Cloud Atlas"
The processes of formation of a separate cloud proceed under the influence of many factors. Clouds and their precipitation play an important role in the formation of various types of weather. Therefore, cloud classification provides specialists with the ability to track the spatial and temporal variability of cloud formations, which is a powerful tool for studying and predicting processes occurring in the atmosphere.
For the first time, an attempt to separate clouds according to their appearance into different groups was made in 1776 by J. B. Lamarck. However, the classification proposed by him, due to its imperfection, did not find wide application.
changes. The first classification of clouds that entered science was developed by the English amateur meteorologist L. Howard in 1803. In 1887, the scientists Hildebrandson in Sweden and Abercrombie in England, having revised the classification of L. Howard, proposed a draft of a new classification, which formed the basis of all subsequent classifications . The idea of creating the first unified cloud atlas was supported by International Conference directors of meteorological services in Munich in 1891. The committee she created prepared and published in 1896 the first International Cloud Atlas with 30 color lithographs. The first Russian edition of this Atlas was published in 1898. The further development of meteorology and the introduction of the concepts of atmospheric fronts and air masses into the practice of synoptic analysis required a much more detailed study of clouds and their systems. This predetermined the need for a significant revision of the classification used at that time, which resulted in the publication in 1930 of a new International Cloud Atlas. This Atlas was published in Russian in 1933 in a somewhat abridged version.
Clouds and precipitation falling from them are among the most important meteorological (atmospheric) phenomena and play a decisive role in the formation of weather and climate, in the distribution of flora and fauna on Earth. By changing the radiation regime of the atmosphere and the earth's surface, clouds have a noticeable effect on the temperature and humidity regime of the troposphere and the surface layer of air, where human life and activity take place.
A cloud is a visible set of droplets and/or crystals suspended in the atmosphere and in the process of continuous evolution, which are products of condensation and/or sublimation of water vapor at altitudes from several tens of meters to several kilometers.
The change in the phase structure of the cloud - the ratio of drops and crystals by mass, number of particles and other parameters per unit volume of air - occurs under the influence of temperature, humidity and vertical movements both inside and outside the cloud. In turn, the release and absorption of heat as a result of phase transitions of water and the presence of the particles themselves in the air flow have an inverse effect on the parameters of the cloudy environment.
According to the phase structure, clouds are divided into three groups.
1. Water, consisting only of drops with a radius of 1-2 microns or more. Drops can exist not only at positive, but also at negative temperatures. The purely drop structure of the cloud is preserved, as a rule, up to temperatures of the order of –10...–15 °C (sometimes even lower).
2. Mixed, consisting of a mixture of supercooled drops and ice crystals at temperatures of –20...–30 °C.
3. Ice, consisting only of ice crystals at sufficiently low temperatures (about -30 ... -40 ° С).
Cloud cover during the day reduces the influx of solar radiation to the earth's surface, and at night noticeably weakens its radiation and, consequently, cooling, very significantly reduces the daily amplitude of air and soil temperatures, which entails a corresponding change in other meteorological quantities and atmospheric phenomena.
Regular and reliable observations of cloud forms and their transformation contribute to the timely detection of dangerous and adverse hydrometeorological phenomena associated with one or another type of clouds.
The program of meteorological observations includes tracking the dynamics of cloud development and determining the following cloud characteristics:
a) the total amount of clouds,
b) the amount of lower clouds,
c) the shape of the clouds,
d) the height of the lower boundary of the clouds of the lower or middle tier (in the absence of clouds of the lower tier).
The results of cloud observations from meteorological observation units in real time using the code KN-01 (the national version of the international code FM 12-IX SYNOP) are regularly transmitted to local forecasting authorities (organizations and divisions of the UGMS) and the Hydrometeorological Research Center of the Russian Federation (Hydrometeorological Center Russia) for synoptic analysis and compilation of weather forecasts of various lead times. In addition, these data are calculated for various time intervals and used for climate assessments and generalizations.
The number of clouds is defined as the total proportion of the sky covered by clouds from the entire visible surface of the sky and is estimated in points: 1 point is 0.1 share (part) of the entire sky, 6 points - 0.6 of the sky, 10 points - the entire sky is covered by clouds .
Long-term observations of clouds have shown that they can be located at different heights, both in the troposphere and in the stratosphere and even in the mesosphere. Tropospheric clouds are usually observed as individual, isolated cloud masses or as a continuous cloud cover. Depending on the structure, clouds are divided in appearance into forms, types and varieties. Noctilucent and mother-of-pearl clouds, in contrast to tropospheric clouds, are observed quite rarely and are characterized by relatively little diversity. The classification of tropospheric clouds by appearance currently used is called the international morphological classification.
Along with the morphological classification of clouds, genetic classification is also used, i.e., classification according to the conditions (reasons) for the formation of clouds. In addition, clouds are classified according to their microphysical structure, i.e., according to the state of aggregation, the type and size of cloud particles, and also according to their distribution within the cloud. In accordance with the genetic classification, clouds are divided into three groups: stratus, undulating and cumulus (convective).
The main distinguishing features in determining the shape of clouds are their appearance and structure. Clouds can be located on different heights in the form of separate isolated masses or a continuous cover, their structure can be different (homogeneous, fibrous, etc.), and the lower surface can be even or dissected (and even torn). In addition, clouds can be dense and opaque or thin - a blue sky, moon or sun shines through them.
The height of clouds of the same shape is not constant and may vary somewhat depending on the nature of the process and local conditions. On average, cloud heights are greater in the south than in the north, and more in summer than in winter. Above the mountainous regions, clouds are located lower than above the plains.
Precipitation is an important characteristic of clouds. Clouds of some forms almost always give precipitation, while others either do not give precipitation at all, or precipitation from them does not reach the surface of the earth. The fact of precipitation, as well as their type and nature of precipitation, serve as additional signs for determining the forms, types and varieties of clouds. The following types of precipitation fall from clouds of certain shapes:
– showers – from cumulonimbus clouds (Cb);
- oblique - from stratocumulus (Ns) in all seasons, from altostratus (As) - in winter and sometimes weak - from stratocumulus (Sc);
– drizzling – from stratus clouds (St).
In the process of development and decay of the cloud, its appearance and structure change, and it can transform from one form to another.
When determining the amount and shape of clouds, only clouds visible from the surface of the earth are taken into account. If the whole sky or part of it is covered with clouds of the lower (middle) tier, and clouds of the middle (upper) tier are not visible, this does not mean that they are absent. They may be above the underlying cloud layers, but this is not taken into account in cloud observations.
Cloudiness- a complex of clouds that appear in a certain place on the planet (point or territory) at a certain moment or period of time.
One or another type of cloudiness corresponds to certain processes occurring in the atmosphere, and therefore portends one or another weather. Knowledge of the types of clouds from the point of view of the navigator is important for predicting weather from local characteristics. For practical purposes, clouds are divided into 10 main forms, which in turn are subdivided by height and vertical extent into 4 types:
Cumulus. Latin name— Cumulus(marked as Cu on weather maps)- separate thick vertically developed clouds. The upper part of the cloud is dome-shaped, with prominences, the lower part is almost horizontal. The average vertical extent of the cloud is 0.5 -2 km. The average height of the lower base from earth's surface– 1.2 km.
- heavy masses of clouds of large vertical development in the form of towers and mountains. The upper part is a fibrous structure, often with projections to the sides in the form of an anvil. The average vertical length is 2-3 km. The average height of the lower base is 1 km. Often give heavy rainfall, accompanied by thunderstorms.
– low, amorphous, layered, almost homogeneous rain clouds dark grey. The lower base is 1-1.5 km. The average vertical extent of the cloud is 2 km. Heavy rain falls from these clouds.
- a uniform light gray foggy veil of continuous low clouds. Often formed from rising fog or turning into fog. The height of the lower base is 0.4–0.6 km. The average vertical extent is 0.7 km.
- Short cloud cover, consisting of separate ridges, waves, plates or flakes, separated by gaps or translucent areas (translucent) or without clearly visible gaps, the fibrous structure of such clouds is more clearly visible near the horizon.
- a fibrous veil of gray or bluish color. The lower base is located at an altitude of 3-5 km. Vertical length - 04 - 0.8 km).
- layers or spots, consisting of strongly flattened rounded masses. The lower base is located at an altitude of 2–5 km. The average vertical extent of the cloud is 0.5 km.
Cirrostratus (Cs) - a thin whitish translucent veil, gradually covering the entire sky. They do not obscure the outer contours of the Sun and Moon, leading to the appearance of a halo around them. The lower boundary of the cloud is at an altitude of about 7 km.
Determination and recording of the total amount of clouds, as well as determination and recording of the amount of clouds of the lower and middle tiers and their heights.
Determination and recording of the total number of clouds
The number of clouds is expressed in points on a 10-point scale from 0 to 10. It is estimated by eye how many tenths of the sky are covered with clouds.
If there are no clouds or cloudiness covers less than 1/10 of the sky, the cloudiness is rated with a score of 0. If 1/10, 2/10, 3/10 of the sky, etc. are covered with clouds, marks are respectively 1, 2, 3, etc. d. The number 10 is set only when the entire sky is completely covered with clouds. If even very small gaps are observed in the sky, 10
If the number of clouds is more than 5 points (that is, half the sky is covered with clouds), it is more convenient to estimate the area not occupied by clouds and subtract the resulting value, expressed in points, from 10. The remainder will show the number of clouds in points.
In order to estimate what part of the sky is free from clouds, it is necessary to mentally sum up all those gaps in the clear sky (windows) that exist between individual clouds or cloud banks. But those gaps that exist within several clouds (cirrus, cirrocumulus, and almost all types of altocumulus) are inherent in them by internal structure and are very small in size, they cannot be summed up. If such gaping clouds cover the entire sky, the Number 10 is put.
Determination and recording of the amount of clouds of the lower and middle tiers and their heights.
In addition to the total number of clouds N, it is necessary to determine the total number of stratocumulus, stratus, cumulus, cumulonimbus and fractonimbus clouds Nh (forms recorded in the “CL” line) or, if not, then the total number in altocumulus, altostratus and nimbostratus clouds (forms written in the line “CM”). The number of these clouds Nh is determined by the same rules as the total number of clouds.
The height of the clouds must be estimated by eye, striving for an accuracy of 50-200 m. If this is difficult, then at least with an accuracy of 0.5 km. If these clouds are located at the same level, then the height of their base is written in the line “h”, if they are located at different levels, the height h of the lowest clouds is indicated. If there are no clouds of the form written in the line “CL”, but clouds of the form written in “cm” are observed, the height of the base of these clouds is recorded in line h. If individual fragments or patches of clouds recorded in the “CL” line (in an amount less than 1 point) are located under a more extensive layer of other clouds of the same forms or forms recorded in the “Sm” line, the height of the base of this layers of clouds, not wisps or scraps.
Cloudiness is determined visually using a 10-point system. If the sky is cloudless or there are one or more small clouds occupying less than one tenth of the entire sky, then the cloudiness is considered to be 0 points. With cloudiness equal to 10 points, the entire sky is covered with clouds. If 1/10, 2/10, or 3/10 parts of the sky are covered by clouds, then the cloudiness is considered to be equal to 1, 2, or 3 points, respectively.
Determination of light intensity and background radiation*
Photometers are used to measure illumination. The deviation of the galvanometer pointer determines the illumination in lux. Photometers can be used.
To measure the level of radiation background and radioactive contamination, dosimeters-radiometers ("Bella", "ECO", IRD-02B1, etc.) are used. Typically, these devices have two modes of operation:
1) assessment of the radiation background in terms of the equivalent dose rate of gamma radiation (μSv/h), as well as contamination in terms of gamma radiation of samples of water, soil, food, crop products, animal husbandry, etc.;
* Units of measurement of radioactivity
Radionuclide activity (А)- decrease in the number of radionuclide nuclei for a certain
fixed time interval:
[A] \u003d 1 Ci \u003d 3.7 1010 dispersal / s \u003d 3.7 1010 Bq.
Absorbed radiation dose (D) is the energy ionizing radiation transferred to a certain mass of the irradiated substance:
[D] = 1 Gy = 1 J/kg = 100 rad.
Equivalent radiation dose (N) is equal to the product of the absorbed dose by
average quality factor of ionizing radiation (K), taking into account biological
logical effect of various radiations on biological tissue:
[N] = 1 Sv = 100 rem.
Exposure dose (X) is a measure of the ionizing effect of radiation, a single
which is equal to 1 Ku/kg or 1 P:
1 P \u003d 2.58 10-4 Ku / kg \u003d 0.88 rad.
Dose rate (exposure, absorbed or equivalent) is the ratio of the dose increment for a certain time interval to the value of this time interval:
1 Sv/s = 100 R/s = 100 rem/s.
2) assessment of the degree of contamination with beta-, gamma-radiating radionuclides of surfaces and samples of soil, food, etc. (particles / min. cm2 or kBq / kg).
The maximum allowable exposure dose is 5 mSv/year.
The level of radiation safety is determined using the example of using a household dosimeter-radiometer (IRD-02B1):
1. Set the operation mode switch to the "µSv/h" position.
2. Turn on the device, for which set the switch "off - on."
in "on" position. Approximately 60 seconds after switching on, the device is ready
to work.
3. Place the device in the place where the equivalent dose rate is determined gamma radiation. After 25-30 s, a value will appear on the digital display, which corresponds to the dose rate of gamma radiation in this place, expressed in microsieverts per hour (µSv/h).
4. For a more accurate estimate, it is necessary to take the average of 3-5 consecutive readings.
The indication on the digital display of the device 0.14 means that the dose rate is 0.14 µSv/h or 14 µR/h (1 Sv = 100 R).
After 25-30 seconds after the start of operation of the device, it is necessary to take three consecutive readings and find the average value. The results are presented in the form of a table. 2.
Table 2. Determining the level of radiation
Instrument readings |
Mean |
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dose rate |
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Registration of the results of microclimatic observations
The data of all microclimatic observations are recorded in a notebook, and then processed and presented in the form of a table. 3.
Table 3. Results of processing microclimatic
observations
Temperature- |
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ra air |
Temperature- |
Humidity |
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on high, |
ra air, |
air on |
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height, % |
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Clouds floating across the sky draw our gaze from early childhood. Many of us liked to peer at their outlines for a long time, inventing what the next cloud looked like - a fairy-tale dragon, an old man's head or a cat running after a mouse.
How I wanted to climb one of them to lie in a soft cotton mass or jump on it, like on a springy bed! But at school, in nature studies, all children learn that in reality they are just large accumulations of water vapor floating at a great height above the ground. What else is known about clouds and cloudiness?
Cloudiness is usually called the mass of clouds that are above the surface of a certain part of our planet at the current time or were there at a certain point in time. It is one of the main weather and climatic factors that prevents both too much heating and cooling of the surface of our planet.
Cloudiness scatters solar radiation, preventing overheating of the soil, but at the same time reflects its own thermal radiation from the Earth's surface. In fact, the role of clouds is similar to that of a blanket, keeping our body temperature stable during sleep.
Aeronautical meteorologists use the so-called 8-oct scale, which divides the sky into 8 segments. The number of clouds visible in the sky and the height of their lower boundaries are indicated in layers from the lower layer to the upper one.
The quantitative expression of cloudiness is today denoted by automatic weather stations in Latin letter combinations:
- FEW - slight scattered cloudiness in 1-2 oktas, or 1-3 points on the international scale;
- NSC - the absence of significant cloudiness, while the number of clouds in the sky can be any, if they bottom line located above 1500 meters, and there are no powerful cumulus and cumulonimbus clouds; 
- CLR - all clouds are above 3000 meters.
Meteorologists distinguish three main forms of clouds:
- cirrus, which are formed at an altitude of more than 6 thousand meters from the smallest ice crystals, into which droplets of water vapor turn, and have the shape of long feathers;
- cumulus, which are located at an altitude of 2-3 thousand meters and look like shreds of cotton wool;
- layered, located one above the other in several layers and, as a rule, covering the entire sky.
Professional meteorologists distinguish several dozen varieties of clouds, which are variants or combinations of three basic forms.
Cloudiness directly depends on the moisture content in the atmosphere, since clouds are formed from molecules of evaporated water condensed into tiny droplets. A significant amount of clouds is formed in the equatorial zone, since the evaporation process is very active there due to high temperature air.
Most often, cumulus and thunderstorm clouds form here. Subequatorial belts are characterized by seasonal cloudiness: in the rainy season, it usually increases, in the dry season it is practically absent.
Cloudiness temperate zones depends on the transport of sea air, atmospheric fronts and cyclones. It is also seasonal in both quantity and shape of clouds. In winter, stratus clouds form most often, covering the sky with a continuous veil. 
By spring, cloudiness usually decreases, and cumulus clouds begin to appear. In summer, the sky is dominated by cumulus and cumulonimbus forms. Clouds are most abundant in autumn with a predominance of stratus and nimbostratus clouds.
For the entire planet as a whole, the quantitative indicator of cloudiness is approximately equal to 5.4 points, and over land the cloudiness is lower - about 4.8 points, and above the sea - 5.8 points. Most cloudiness occurs over the northern part Pacific Ocean and the Atlantic, where its value reaches 8 points. Over deserts, it does not exceed 1-2 points.
