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Average cloudy. Determining and recording the total number of clouds. Clouds of large vertical development. These include

Humidity

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

absolute humidity but - 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.

In the 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 decrease in temperature occurs adiabatically in the rising moist air and leads to condensation or sublimation of water vapor, which is the main reason for the formation of clouds. 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,

In 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- separate thin light clouds of white color, transparent, fibrous or filamentous structure have 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.

At a certain height above the 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 in the 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 areas.

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; in the central months of spring and autumn, the diurnal variation is smoothed out, and the maximum can shift 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).

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 in 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.

The concept of "cloudiness" refers to the number of clouds observed in one place. Clouds, in turn, are called atmospheric phenomena formed by a suspension of water vapor. The classification of clouds includes many of their types, divided by size, shape, nature of formation and altitude.

In everyday life, special terms are used to measure cloudiness. Expanded scales for measuring this indicator are used in meteorology, maritime affairs and aviation.

Meteorologists use a ten-point cloud scale, which is sometimes expressed as a percentage of coverage of the observable sky (1 point - 10% coverage). In addition, the height of cloud formation is divided into upper and lower tiers. The same system is used in maritime affairs. Aeronautical meteorologists use a system of eight octants (parts of the visible sky) with a more detailed indication of the height of the clouds.

A special device is used to determine the lower boundary of the clouds. But only aviation weather stations are in dire need of it. In other cases, a visual assessment of the height is made.

Cloud types

Cloudiness plays an important role in the formation of weather conditions. Cloud cover prevents the Earth's surface from heating and prolongs the process of its cooling. Cloud cover significantly reduces daily temperature fluctuations. Depending on the amount of clouds at a certain time, several types of cloudiness are distinguished:

  1. "Clear or partly cloudy" corresponds to cloudiness of 3 points in the lower (up to 2 km) and middle tiers (2 - 6 km) or any amount of clouds in the upper (above 6 km).
  2. "Changing or variable" - 1-3/4-7 points in the lower or middle tier.
  3. "With clearings" - up to 7 points of total cloudiness of the lower and middle tiers.
  4. "Cloudy, cloudy" - 8-10 points in the lower tier or not translucent clouds on average, as well as with precipitation in the form of rain or snow.

Types of clouds

The world classification of clouds distinguishes many types, each of which has its own Latin name. It takes into account the shape, origin, height of education and a number of other factors. The classification is based on several types of clouds:

  • Cirrus clouds are thin filaments of white. They are located at an altitude of 3 to 18 km, depending on the latitude. They consist of falling ice crystals, to which they owe their appearance. Among the cirrus at a height of over 7 km, clouds are divided into cirrocumulus, altostratus, which have a low density. Below, at an altitude of about 5 km, there are altocumulus clouds.
  • Cumulus clouds are dense formations of white color and a considerable height (sometimes more than 5 km). They are located most often in the lower tier with vertical development in the middle. Cumulus clouds at the upper boundary of the middle tier are called altocumulus.
  • Cumulonimbus, shower and thunderclouds, as a rule, are located low above the Earth's surface 500-2000 meters, are characterized by precipitation in the form of rain, snow.
  • Stratus clouds are a layer of low-density suspended matter. They let in the light of the sun and moon and are at an altitude of between 30 and 400 meters.

Cirrus, cumulus and stratus types, mixing, form other types: cirrocumulus, stratocumulus, cirrostratus. In addition to the main types of clouds, there are other, less common ones: silvery and mother-of-pearl, lenticular and vymeform. And clouds formed by fires or volcanoes are called pyrocumulative.

As you know, many of the industries, agriculture, transport services are very dependent on the efficiency, timeliness and reliability of the forecasts of the Federal Meteorological Service. Early warning of dangerous and especially dangerous weather phenomena, timely filing of storm warnings are all necessary conditions for the successful and safe operation of many sectors of the economy and transport. For example, long-term meteorological forecasts play a decisive role in the organization of agricultural production.

One of the most important parameters that determine the ability to predict dangerous weather conditions is such an indicator as the height of the base of the clouds.

In meteorology, cloud height is the height of the cloud base above the earth's surface.

To understand the importance of conducting research to determine the height of clouds, it is worth mentioning the fact that clouds can be of different types. For different types of clouds, the height of their lower boundary may vary within certain limits, and the average value of the height of the clouds has been revealed.

So clouds can be:

Stratus clouds (average height 623 m.)

Rain clouds (average height 1527 m.)

Cumulus (top) (1855)

Cumulus (base) (1386)

Thunderstorm (top) (average height 2848 m.)

Thunderstorm (base) (average height 1405 m.)

False pinnate (average height 3897 m.)

Stratocumulus (average height 2331 m.)

High cumulus (below 4000 m) (average height 2771 m)

High cumulus (above 4000 m) (average height 5586 m)

Cirrocumulus (average height 6465 m)

Low cirrostratified (average height 5198 m.)

High cirrocumulus (average height 9254 m.)

Cirrus (average height 8878 m.)

As a rule, the height of the clouds of the lower and middle tiers is measured, not exceeding 2500 m. At the same time, the height of the lowest clouds from their entire array is determined. In fog, the height of the clouds is considered to be zero, and, in this case, “vertical visibility” is measured at airports.



To determine the height of the lower boundary of the clouds, the method of light location is used. In Russia, a meter is produced for these purposes, in which a flash lamp is used as a source of pulses and light.

The height of the lower boundary of the clouds by the method of light location using DVO-2 is determined by measuring the time it takes for a light pulse to travel from the light emitter to the cloud and back, as well as converting the obtained time value into a value of cloud height proportional to it. Thus, a light pulse is sent by the emitter and, after reflection, is received by the receiver. In this case, the emitter and receiver must be located in close proximity to each other.


Structurally, the DVO-2 meter is a complex of several separate devices:

transmitter and receiver,

communication lines,

measuring block,

remote control.


The DVO-2 cloud height meter can operate autonomously with a measuring unit, complete with a remote control and as part of automated meteorological stations.

The transmitter consists of a flash tube, capacitors feeding it and a parabolic reflector. The reflector, together with the lamp and capacitors, is installed in a gimbal suspension enclosed in a housing with an opening lid.

The receiver consists of a parabolic mirror, a photodetector, a photoamplifier, also installed in a gimbal suspension and located in a housing with an opening lid.

The transmitter and receiver should be located near the main observation point. On runways, the transmitter and receiver are located at the nearest locator beacons at both ends of the runway.

The measuring unit, intended for collecting and processing information, consists of a measuring board, a high-voltage unit and a power supply unit.

The remote control includes a keyboard and indication board and a control board.

The signal from the receiver via a two-wire potentially isolated communication line with unipolar signals and a rated current (20 ± 5) mA is transmitted to the measuring unit, and from there to the remote control. Depending on the configuration, instead of a remote control for processing and displaying on the operator's display, the signal can be transmitted to the central system of the weather station.

The DVO-2 cloud height meter can operate either continuously or as needed. The remote control has a serial RS-232 interface intended for working with a computer. Information from DVO-2 meters can be transmitted over a communication line at a distance of up to 8 km.

Processing of measurement results on the measuring unit DVO-2 includes:

Averaging results over 8 measured values;

Exclusion from the number of measurements of those results in which there is a short-term loss of the reflected signal. Those. exclusion of the "gap in the clouds" factor;

The issuance of a signal about the "absence of clouds" in the event that among the 15 observations made, 8 significant ones are not recruited;

Exclusion of the so-called locals - false reflection signals.