How is cloud cover measured? Cloudy. What is cloud cover? Clouds of large vertical development. These include

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 of ionizing radiation transferred a certain mass 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.

Determining the level of radiation safety

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 seconds, the digital display will display a value that corresponds to the dose rate of gamma radiation in a given 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
				dose rate

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-

ra air

Temperature-

Humidity

on high,

ra air,

air on

height, %

Humidity

Humidity is the content of water vapor in it. Its characteristics are:

absolute humidity a - the amount of water vapor (in g) in 1 m 3 of air;

saturating (saturated) steam BUT - the amount of steam (in g) required to completely saturate a unit volume (its elasticity is denoted by the letter E);

relative humidity R is the ratio of absolute humidity to saturating steam, expressed as a percentage ( R=100% × a/A);

Dew point is the temperature at which air would reach saturation at a given moisture content and constant pressure.

AT equatorial zone and subtropics, the absolute humidity near the ground reaches 15 - 20 g / m 3. In temperate latitudes in summer - 5 - 7 g / m 3, in winter (as well as in the Arctic basin) it decreases to 1 g / m 3 and below. The amount of water vapor in the air drops rapidly with altitude. Humidity affects the change in air temperature, as well as the formation of clouds, fogs, precipitation.

Along with the process of evaporation of water in the atmosphere, the reverse process also occurs - the transition of water vapor with a decrease in temperature into a liquid or directly into a solid state. The first process is called condensation, second - sublimation.

The temperature decrease occurs adiabatically in the rising humid air and leads to condensation or sublimation of water vapor, which is main reason cloud formation. The reasons for the rise of air in this case may be: 1) convection, 2) upward sliding along an inclined frontal surface, 3) undulating movements, 4) turbulence.

In addition to the above, a decrease in temperature can also occur due to radiative cooling (from radiation) of the upper layers of inversions or the upper boundary of clouds.

Condensation occurs only if the air is saturated with water vapor and there are condensation nuclei in the atmosphere. Condensation nuclei are the smallest solid, liquid and gaseous particles that are constantly present in the atmosphere. The most common are the nuclei containing compounds of chlorine, sulfur, nitrogen, carbon, sodium, calcium, and the most common nuclei are compounds of sodium and chlorine, which have hygroscopic properties.

Condensation nuclei enter the atmosphere mainly from the seas and oceans (about 80%) by evaporation and spraying them from the water surface. In addition, the sources of condensation nuclei are products of combustion, soil weathering, volcanic activity, etc.

As a result of condensation and sublimation, tiny water droplets (with a radius of about 50 mk) and ice crystals that look like a hexagonal prism. Their accumulation in the surface layer of air gives a haze or fog in the overlying layers of the cloud. The merging of small cloud drops or the growth of ice crystals leads to the formation of various kinds of precipitation: rain, snow.

Clouds can consist only of drops, only of crystals, and be mixed, i.e., consist of drops and crystals. Water droplets in clouds at negative temperatures are in a supercooled state. In most cases, liquid drop clouds are observed down to a temperature of -12 ° C, purely icy (crystalline) clouds - at temperatures below -40 ° C, mixed clouds - from -12 to -40 ° C.

Clouds are watery. Water content is the amount of water in grams contained in one cubic meter of a cloud. (g / m 3). Water content in liquid drop clouds ranges from 0.01 to 4 g per cubic meter of cloud mass (in some cases, more than 10 g/m 3). In ice clouds, water content is less than 0.02 g / m 3, and in mixed clouds up to 0.2-0.3 g/m 3 . Moisture should not be confused with moisture.

Clouds are classified:

By the height of the lower border by 3 (sometimes 4) tiers,

By origin (genetic classification) into 3 groups,

By appearance(morphological classification) are divided into several forms:

The main forms are distinguished:

Cumulus clouds are white, gray, dark gray separate formations in the form of heaps of various shapes.

Cirrus- individual thin light clouds white color, transparent, fibrous or filamentous structures are in the form of hooks, threads, feathers or stripes.

stratus clouds- are a uniform gray cover, of varying transparency.

cirrocumulus clouds, which are small white flakes or small balls (lambs), resembling lumps of snow,

Cirrostratus clouds that look like a white veil, often covering the entire sky, and giving it a milky white hue.

Stratocumulus gray clouds with dark stripes - cloudy shafts.

Other features of the appearance (presence of waviness, specific cloud shapes) and association with precipitation are also noted. In total, there are 10 main forms of clouds and 70 of their varieties.

The shape of clouds is determined by observing them in accordance with the accepted classification using a specially published Cloud Atlas.

Clouds that form within air masses are called intramass, formed on atmospheric fronts - frontal arising above the mountains when air flows over obstacles (mountains) - orographic.

Groups	Education process	Tier
Lower (0 - 2000m). Clouds of vertical development.	Medium (2000 - 6000 m).	Upper (above 6000m).
Cumulus	Convection in the presence of a retarding layer.	Cumulus (flat clouds).	Altocumulus: - flaky; - tower-shaped.	Cirrocumulus flaky
Vertical development: the intrusion of cold air under warm air.	Cumulonimbus. Powerful cumulus (upper limit - to the tropopause).
Layered-shaped	Ascending sliding of warm air along gentle frontal sections or over a cold underlying surface.	Layered rain. Fractured rain (stratus or stratocumulus)	High-layered: - thin. - dense	Cirrus. Cirrostratus
Wavy	Over-inversion: ascending sliding of warm air over the inversion layer with a slight slope.	Stratocumulus dense	Altocumulus Dense	Cirrocumulus undulate
Subinversion: turbulence, radiation, mixing in the boundary layer.	Stratocumulus translucent. layered	Altocumulus translucent: - undulate, - ridges, - lentiformes

When specifying the height of the upper and lower boundaries of the clouds, one must keep in mind that they can be both quite clear and extremely blurry. Especially dangerous is the transitional pre-cloud layer, reaching 200 m under the sub-inversion clouds.

Artificial cirrus clouds that arise behind a flying aircraft in the upper troposphere should be singled out as a separate group. They are called contrails (sometimes contrails). They arise as a result of the sublimation of water vapor contained in the exhaust gases of the engine.

Clouds floating across the sky attract our attention 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 the lessons of natural history, all children learn that in fact 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 - what is this phenomenon?

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.

Cloud measurement

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 their lower limit is located above 1500 meters, and there are no powerful cumulus and cumulonimbus clouds;


- CLR - all clouds are above 3000 meters.

cloud shapes

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.

What does cloudiness depend on?

Cloudiness directly depends on the moisture content in the atmosphere, since clouds are formed from evaporated water molecules 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 the high air temperature.

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. The greatest cloud cover is formed over the northern part of the Pacific Ocean and the Atlantic, where its value reaches 8 points. Over deserts, it does not exceed 1-2 points.

Due to the shielding effect, it prevents both the cooling of the Earth's surface due to its own thermal radiation and its heating by solar radiation, thereby reducing seasonal and daily fluctuations in air temperature.

Cloud Characteristics

Number of clouds

The amount of clouds is the degree of cloud coverage of the sky (at a certain moment or on average over a certain period of time), expressed on a 10-point scale or as a percentage of coverage. The modern 10-point scale of cloudiness was adopted at the first Marine International Meteorological Conference (Brussels, city).

When observing at meteorological stations, the total amount of clouds and the amount of lower clouds are determined; these numbers are recorded in the weather diaries through a fractional line, for example 10/4 .

In aviation meteorology, an 8-oct scale is used, which is easier for visual observation: the sky is divided into 8 parts (that is, in half, then in half and again), cloudiness is indicated in octants (eighths of the sky). In aviation meteorological weather reports (METAR, SPECI, TAF), the amount of clouds and the height of the lower boundary are indicated by layers (from the lowest to the highest), while the gradations of quantity are used:

• FEW - minor (scattered) - 1-2 octants (1-3 points);
• SCT - scattered (separate) - 3-4 octants (4-5 points);
• BKN - significant (broken) - 5-7 oktants (6-9 points);
• OVC - solid - 8 octants (10 points);
• SKC - clear - 0 points (0 octants);
• NSC - no significant clouds (any amount of clouds with a base height of 1500 m and above, in the absence of cumulonimbus and powerful cumulus clouds);
• CLR - no clouds below 3000 m (abbreviation used in reports generated by automatic weather stations).

cloud shapes

The observed forms of clouds are indicated (in Latin designations) in accordance with the international classification of clouds.

Cloud base height (CLB)

The VNGO of the lower tier is determined in meters. At a number of weather stations (especially aviation ones), this parameter is measured by an instrument (error 10-15%), at the rest - visually, approximately (in this case, the error can reach 50-100%; visual VNGO is the most unreliably determined weather element). Cloudiness can be divided into 3 tiers (lower, middle and upper) depending on the VNGO. The lower tier includes (up to about a height of 2 km): stratus (precipitation may fall in the form of drizzle), nimbostratus (overdose precipitation), stratocumulus (in aviation meteorology, stratified and ruptured rain are also noted) clouds. Middle layer (approximately from 2 km to 4-6 km): altostratus and altocumulus. Upper layer: cirrus, cirrocumulus, cirrostratus clouds.

Cloud top height

It can be determined from the data of aircraft and radar sounding of the atmosphere. It is usually not measured at weather stations, but in aviation weather forecasts for routes and areas of flight, the expected (predicted) height of the top of the clouds is indicated.

see also

Sources

Seasons tropical seasons Weather conditions Precipitation Forecast and weather diary

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An excerpt characterizing Cloudiness

Finally, the headman Dron entered the room and, bowing low to the princess, stopped at the lintel.
Princess Mary walked across the room and stopped in front of him.
“Dronushka,” said Princess Mary, who saw in him an undoubted friend, that very Dronushka who, from his annual trip to the fair in Vyazma, brought her every time and served his special gingerbread with a smile. “Dronushka, now, after our misfortune,” she began and fell silent, unable to speak further.
“We all walk under God,” he said with a sigh. They were silent.
- Dronushka, Alpatych has gone somewhere, I have no one to turn to. Are they telling me the truth that I can't even leave?
“Why don’t you go, your excellency, you can go,” said Dron.
- I was told that it was dangerous from the enemy. My dear, I can’t do anything, I don’t understand anything, there’s no one with me. I certainly want to go at night or tomorrow early in the morning. Drone was silent. He glanced frowningly at Princess Marya.
“There are no horses,” he said, “I also told Yakov Alpatych.
- Why not? - said the princess.
“All from God’s punishment,” said Dron. - What horses were dismantled under the troops, and which died, now what a year. Not to feed the horses, but not to die of hunger ourselves! And so they sit for three days without eating. There is nothing, ruined completely.
Princess Mary listened attentively to what he was saying to her.
Are the men ruined? Do they have any bread? she asked.
“They die of starvation,” said Dron, “let alone carts…
“But why didn’t you say, Dronushka?” Can't help? I will do everything I can ... - It was strange for Princess Mary to think that now, at such a moment, when such grief filled her soul, there could be people rich and poor and that the rich could not help the poor. She vaguely knew and heard that there was master's bread and that it was given to peasants. She knew, too, that neither her brother nor her father would have denied the need to peasants; she was only afraid to make a mistake somehow in her words about this distribution of bread to the peasants, which she wanted to dispose of. She was glad that she had an excuse for caring, one for which she was not ashamed to forget her grief. She began to ask Dronushka for details about the needs of the peasants and about what is masterful in Bogucharov.
“We have the master’s bread, bro?” she asked.
“The Lord’s bread is whole,” Dron said proudly, “our prince did not order to sell it.
“Give him to the peasants, give him everything they need: I give you permission in the name of your brother,” said Princess Mary.
Drone did not answer and took a deep breath.
- You give them this bread, if it will be enough for them. Distribute everything. I command you in the name of a brother, and tell them: whatever is ours, so is theirs. We will spare nothing for them. So you say.
Drone gazed at the princess intently while she spoke.
“Fire me, mother, for God’s sake, send me the keys to accept,” he said. - He served twenty-three years, did not do anything bad; quit, for God's sake.
Princess Mary did not understand what he wanted from her and why he asked to be fired. She answered him that she never doubted his devotion and that she was ready to do everything for him and for the peasants.

An hour later, Dunyasha came to the princess with the news that Dron had come and all the peasants, on the orders of the princess, had gathered at the barn, wanting to talk with the mistress.
“Yes, I never called them,” said Princess Marya, “I only told Dronushka to distribute bread to them.
- Only for God's sake, Princess Mother, order them to drive away and do not go to them. It’s all a deception,” Dunyasha said, “but Yakov Alpatych will come, and we’ll go ... and you don’t mind ...

At some height above earth's surface and consist of water droplets or ice crystals, or both. The whole variety of clouds can be reduced to several types. The currently generally accepted international classification of clouds is based on two features: the appearance and the height of their lower boundary.

In appearance, clouds are divided into three classes: separate, unrelated cloud masses, layers with an inhomogeneous surface, and layers in the form of a homogeneous veil. All these forms can occur at different heights, differing in the density and size of external elements (lambs, swellings, ridges, ripples, etc.)

According to the height of the lower base above the earth's surface, clouds are divided into 4 tiers: upper (Ci Cc Cs - height more than 6 km), middle (Ac As - height from 2 to 6 km), lower (Sc St Ns - height less than 2 km), vertical development (Cu Cb - can belong to different tiers, and in the most powerful cumulonimbus clouds (Cb) the base is located on the lower tier, and the top can reach the upper one).

Cloud cover largely determines the amount of solar radiation reaching the Earth's surface and is a source of precipitation, thus influencing the formation of weather and climate.

The amount of clouds in Russia is distributed rather unevenly. The most cloudy are areas subject to active cyclonic activity, characterized by developed advection of wet. These include the northwest of the European part of Russia, the coast of Kamchatka, Sakhalin, the Kuril and. The average annual amount of total cloudiness in these areas is 7 points. A significant part of Eastern Siberia is characterized by a lower average annual amount of clouds - from 5 to 6 points. This relatively cloudy region of the Asian part of Russia is within the scope of the Asian.

The distribution of the average annual amount of low cloudiness generally follows the distribution of the total cloudiness. The largest amount of low level clouds also occurs in the northwest of the European part of Russia. Here they are predominant (only 1-2 points less than the amount of total cloudiness). The minimum number of clouds of the lower tier is noted, especially in (no more than 2 points), which is typical of the continental climate of these areas.

The annual course of the amount of both total and lower cloudiness in the European part of Russia is characterized by minimum values ​​in summer and maximum values ​​in late autumn and winter, when the influence is especially pronounced. A directly opposite annual course of the amount of total and lower cloudiness is observed on Far East, and . Here, the largest number of clouds occurs in July, when the summer monsoon is in effect, bringing a large amount of water vapor from the ocean. The cloudiness minimum is observed in January during the period of the greatest development of the winter monsoon, with which dry cooled continental air from the mainland enters these regions.

The daily course of the total number of clouds throughout Russia is characterized by the following features:

1) its amplitude in most of the territory does not exceed 1-2 points (with the exception of the central regions of the European part of Russia, where it increases to 3 points);

2) the number of clouds during the day is greater than at night, while in January the maximum falls on the morning hours; during the central months of spring and autumn daily course smoothed, and the maximum can be shifted by different hours of the day; in April, the diurnal variation is closer to the summer type, and in October, to the winter type;

3) the daily course of the lower cloudiness practically repeats the daily course of the general cloudiness.

The distribution of clouds by form is characterized by relative constancy in time and space. Almost over the entire territory of Russia, among the clouds of the upper tier, Ci of the middle tier - Ac of the lower tier - Sc and Ns prevail

In the annual course in summer, there is a predominance of cumulus (Cu) and stratocumulus (Sc), while the frequency of occurrence of stratus (St) and nimbostratus (Ns), which are frontal, is small, since in summer conditions are relatively rarely created for active cyclonic activity. The winter, spring and autumn periods in most of Russia are characterized by an increase in the frequency of altostratus (As), altocumulus (Ac) and stratocumulus (Sc) clouds, while in the European part of Russia there is a slight increase in the frequency of stratus and stratus -cumulus clouds (St).