Humidity coefficient. How is the moisture coefficient determined and why is this indicator so important? In which regions of Russia is the coefficient greater than one?

Task 1.

Calculate the moisture coefficient for the points indicated in the table, determine in which natural zones they are located and what moisture is typical for them.

The moisture coefficient is determined by the formula:

K is the moisture coefficient in the form of a fraction or in %; P - amount of precipitation in mm; Em - volatility in mm. According to N.N. Ivanov, the moisture coefficient for the forest zone is 1.0-1.5; forest-steppe 0.6 - 1.0; steppes 0.3 - 0.6; semi-deserts 0.1 - 0.3; deserts less than 0.1.

Characteristics of humidification by natural zones

Volatility	Humidity coefficient	Hydration	Natural area
		insufficient	forest-steppe
		insufficient
		insufficient
		insufficient	semi-desert

To approximate moisture conditions, a scale is used: 2.0 - excessive moisture, 1.0-2.0 - satisfactory moisture, 1.0-0.5 - dry, insufficient moisture, 0.5 - dry

For 1 point:

K = 520/610 K = 0.85

Dry, insufficient moisture, natural zone - forest-steppe.

For 2 points:

K = 110/1340 K = 0.082

Dry, insufficient moisture, natural area - desert.

For 3 points:

K = 450/820 K = 0.54

Dry, insufficient moisture, natural zone - steppe.

For 4 points:

K = 220/1100 K = 0.2

Dry, insufficient moisture, natural zone - semi-desert.

Task 2.

Calculate the humidification coefficient for Vologda region, If annual quantity Precipitation averages 700 mm, evaporation is 450 mm. Draw a conclusion about the nature of moisture in the area. Consider how moisture will change under different hilly terrain conditions.

The humidification coefficient (according to N. N. Ivanov) is determined by the formula:

where, K is the moisture coefficient in the form of a fraction or in %; P - amount of precipitation in mm; Em - volatility in mm.

K = 700/450 K = 1.55

Conclusion: In the Vologda region, located in the natural zone - taiga, there is excessive moisture, because humidification coefficient is greater than 1.

Humidification will vary in different hilly terrain conditions, depending on: geographical latitude terrain, occupied area, proximity to the ocean, relief height, moisture coefficient, underlying surface, slope exposure.

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The humidification coefficient is a special indicator developed by meteorologists to assess the degree of climate humidity in a particular region. It was taken into account that climate is long-term characteristics weather conditions in the area. Therefore, it was also decided to consider the humidification coefficient over a long time frame: as a rule, this coefficient is calculated based on data collected during the year.

Thus, the humidification coefficient shows how much precipitation falls during this period in the region in question. This, in turn, is one of the main factors determining the predominant type of vegetation in this area.

Humidity coefficient calculation

The formula for calculating the humidification coefficient is as follows: K = R / E. In this formula, the symbol K denotes the actual humidification coefficient, and the symbol R denotes the amount of precipitation that fell in a given area during the year, expressed in millimeters. Finally, the symbol E represents the amount of precipitation from the earth's surface over the same period of time.

The indicated amount of precipitation, which is also expressed in millimeters, depends on the temperature in a given region during a particular period of time and other factors. Therefore, despite the apparent simplicity of the given formula, the calculation of the humidification coefficient requires a large number of preliminary measurements using precision instruments and can only be carried out by a sufficiently large team of meteorologists.

In turn, the value of the moisture coefficient in a specific area, taking into account all these indicators, as a rule, allows us to determine with a high degree of reliability which type of vegetation is predominant in this region. So, if the humidification coefficient exceeds 1, this indicates high level humidity in a given area, which entails the predominance of vegetation types such as taiga, tundra or forest-tundra.

A sufficient level of humidity corresponds to a humidification coefficient equal to 1, and, as a rule, is characterized by a predominance of mixed or. A humidification coefficient ranging from 0.6 to 1 is typical for forest-steppe areas, from 0.3 to 0.6 - for steppes, from 0.1 to 0.3 - for semi-desert areas, and from 0 to 0.1 - for deserts .

The moisture content of an area is determined not only by the amount of precipitation, but also by evaporation. With the same amount of precipitation, but different evaporation, moisture conditions can be different.

To characterize humidification conditions, humidification coefficients are used. There are more than 20 ways to express it. The most common are the following indicators humidification:

Hydrothermal coefficient G.T. Selyaninova.

where R is monthly precipitation;

Σt – sum of temperatures per month (close to the evaporation rate).

Vysotsky-Ivanov humidification coefficient.

where R is the amount of precipitation for the month;

E p – monthly evaporation.

Humidification coefficient is about 1 – normal humidification, less than 1 – insufficient, more than 1 – excessive.

Radiation index of dryness M.I. Budyko.

where R i is the radiation dryness index, it shows the ratio of the radiation balance R to the amount of heat Lr required to evaporate precipitation per year (L is the latent heat of evaporation).

The radiation dryness index shows what proportion of residual radiation is spent on evaporation. If there is less heat than is required to evaporate the annual amount of precipitation, there will be excess moisture. At R i 0.45, moisture is excessive; at R i = 0.45-1.00, the moisture is sufficient; at R i = 1.00-3.00, the moisture is insufficient.

Atmospheric humidification

Precipitation amount excluding landscape conditions– an abstract quantity, because it does not determine the moisture conditions of the territory. Thus, in the tundra of Yamal and the semi-deserts of the Caspian lowland, the same amount of precipitation falls - about 300 mm, but in the first case there is excessive moisture, there is a lot of swamping, in the second there is insufficient moisture, the vegetation here is dry-loving, xerophytic.

Humidification of a territory is understood as the relationship between the amount of precipitation ( R), precipitation in a given area, and evaporation ( E n) for the same period (year, season, month). This ratio, expressed as a percentage or fraction of a unit, is called the moisture coefficient ( K yв = R/E n) (according to N.N. Ivanov). The humidification coefficient shows either excessive moisture (K uv > 1), if precipitation exceeds the evaporation possible at a given temperature, or various degrees of insufficient moisture (K uv<1), если осадки меньше испаряемости.

The nature of moisture, i.e. the ratio of heat and moisture in the atmosphere, is the main reason for the existence of natural plant zones on Earth.

Based on hydrothermal conditions, several types of territories are distinguished:

1. Areas with excess moisture – TO UV is greater than 1, i.e. 100-150%. These are zones of tundra and forest-tundra, and with sufficient heat - forests of temperate, tropical and equatorial latitudes. Such waterlogged areas are called humid, and wetlands are called extra-humid (Latin humidus - wet).

2. Territories of optimal (sufficient) moisture are narrow zones where TO uv about 1 (approximately 100%). Within their limits, there is a proportionality between the amount of precipitation and evaporation. These are narrow strips of broad-leaved forests, sparse variable-humid forests and humid savannas. The conditions here are favorable for the growth of mesophilic plants.

3. Territories of moderately insufficient (unstable) moisture. There are different degrees of unstable moisture: areas with TO HC = 1-0.6 (100-60%) are typical for meadow steppes (forest-steppes) and savannas, with TO HC = 0.6-0.3 (60-30%) – dry steppes, dry savannas. They are characterized by a dry season, which makes agricultural development difficult due to frequent droughts.

4. Territories of insufficient moisture. There are arid zones (Latin aridus - dry) with TO HC = 0.3-0.1 (30-10%), semi-deserts and extra-arid zones with TO HC less than 0.1 (less than 10%) – deserts.

In areas with excessive moisture, the abundance of moisture negatively affects the processes of soil aeration (ventilation), i.e., the gas exchange of soil air with atmospheric air. A lack of oxygen in the soil is formed due to the filling of the pores with water, which is why air does not flow there. This disrupts biological aerobic processes in the soil, and the normal development of many plants is disrupted or even stopped. In such areas, hygrophyte plants grow and hygrophilous animals live, which are adapted to damp and humid habitats. To involve territories with excess moisture in economic, primarily agricultural, turnover, drainage reclamation is necessary, i.e., measures aimed at improving the water regime of the territory, drainage excess water(drainage).

There are more areas on Earth with insufficient moisture than waterlogged ones. In arid zones, farming without irrigation is impossible. The main reclamation measures in them are irrigation - artificial replenishment of moisture reserves in the soil for the normal development of plants and watering - the creation of sources of moisture (ponds, wells and other reservoirs) for domestic and economic needs and watering for livestock.

Under natural conditions, in deserts and semi-deserts grow plants adapted to dryness - xerophytes. They usually have a powerful root system capable of extracting moisture from the soil, small leaves, sometimes turned into needles and thorns in order to evaporate less moisture, stems and leaves are often covered with a waxy coating. A special group of plants among them are succulents that accumulate moisture in their stems or leaves (cacti, agaves, aloe). Succulents grow only in warm tropical deserts, where there are no negative air temperatures. Desert animals - xerophiles - are also adapted to dryness in different ways, for example, they hibernate during the driest period (gophers), and are content with the moisture contained in their food (some rodents).

Droughts are common in areas with insufficient moisture. In deserts and semi-deserts these are annual phenomena. In the steppes, which are often called the arid zone, and in the forest-steppe, droughts occur in the summer once every few years, sometimes affecting the end of spring - the beginning of autumn. Drought is a long (1-3 months) period without rain or with very little rainfall, at elevated temperatures and low absolute and relative humidity of air and soil. There are atmospheric and soil droughts. Atmospheric drought occurs earlier. Due to high temperatures and a large moisture deficit, plant transpiration increases sharply; the roots do not have time to supply moisture to the leaves, and they wither. Soil drought is expressed in the drying out of the soil, due to which the normal functioning of plants is completely disrupted and they die. Soil drought is shorter than atmospheric drought due to the spring reserves of moisture in the soil and groundwater. Droughts are caused by anticyclonic weather patterns. In anticyclones, the air descends, adiabatically heats up and dries out. Along the periphery of anticyclones, winds are possible - hot winds with high temperatures and low relative humidity (up to 10–15%), which increase evaporation and have an even more destructive effect on plants.

In the steppes, irrigation is most effective when there is sufficient river flow. Additional measures include snow accumulation - maintaining stubble in the fields and planting shrubs along the edges of beams to prevent snow from blowing into them, and snow retention - rolling snow, creating snow banks, covering the snow with straw in order to increase the duration of snow melting and replenish groundwater reserves. Forest shelterbelts are also effective, as they delay the runoff of melted snow water and lengthen the snowmelt period. Windbreaks (windbreaks) of long forest strips, planted in several rows, weaken the speed of winds, including dry winds, and thereby reduce moisture evaporation.

Literature

Zubaschenko E.M. Regional physical geography. Climates of the Earth: educational and methodological manual. Part 1. / E.M. Zubaschenko, V.I. Shmykov, A.Ya. Nemykin, N.V. Polyakova. – Voronezh: VSPU, 2007. – 183 p.

Calculated by the formula,

where is the moisture coefficient,

R - average annual precipitation, in mm.

E is the evaporation value (the amount of moisture that can evaporate from the water surface at a given temperature), in mm.

The following types of territory are distinguished:

When >1 - excessive moisture ( tundra, forest-tundra, taiga, and with a sufficient amount of heat, forests of temperate and equatorial latitudes) - humid territories

At ≈1 - sufficient moisture ( mixed or broadleaf forests)

At 0.3< <1 - увлажнение недостаточное (если <0.6 - steppe, >0.6 - forest-steppe) There are different degrees of unstable moisture: areas with TO HC = 1-0.6 (100-60%) are typical for meadow steppes ( forest-steppe) and savannas, with TO HC = 0.6-0.3 (60-30%) – dry steppes, dry savannas. They are characterized by a dry season, which makes agricultural development difficult due to frequent droughts. In the steppes, irrigation is most effective when there is sufficient river flow. Additional measures include snow accumulation - maintaining stubble in the fields and planting shrubs along the edges of beams to prevent snow from blowing into them, and snow retention - rolling snow, creating snow banks, covering the snow with straw in order to increase the duration of snow melting and replenish groundwater reserves. Forest shelterbelts are also effective, as they delay the runoff of melted snow water and lengthen the snowmelt period. Windbreaks (windbreaks) of long forest strips, planted in several rows, weaken the speed of winds, including dry winds, and thereby reduce moisture evaporation.

At<0.3 - скудное увлажнение (если <0.1 - desert, >0.1 - semi-desert) extaarid zones The main reclamation measures in them are irrigation - artificial replenishment of moisture reserves in the soil for the normal development of plants and watering - the creation of sources of moisture (ponds, wells and other reservoirs) for domestic and economic needs and watering for livestock.

To assess moisture in a given landscape, it is also used radiation dryness index, which is the reciprocal of the humidification coefficient. And it is calculated by the formula

5. Air humidity. Main factors influencing the geographical distribution of humidity. Hydrometeors.

The Earth's atmosphere contains about 14 thousand km 3 of water vapor. Water enters the atmosphere as a result of evaporation from the underlying surface.

Evaporation. The process of evaporation from the surface of water is associated with the continuous movement of molecules inside the liquid. Water molecules move in different directions and at different speeds. In this case, some molecules located at the surface of the water and having a high speed can overcome the forces of surface adhesion and jump out of the water into the adjacent layers of air.

The rate and amount of evaporation depend on many factors, primarily on temperature and wind, on the lack of humidity and pressure. The higher the temperature, the more water can evaporate. The role of wind in evaporation is clear. The wind constantly carries away the air that has managed to absorb a certain amount of water vapor from the evaporating surface, and continuously brings new portions of drier air. According to observations, even a weak wind (0.25 m/sec) increases evaporation almost threefold.

When evaporating from the land surface, vegetation plays a huge role, since, in addition to evaporation from the soil, evaporation by vegetation occurs (transpiration).

IN atmosphere moisture condenses, moves with air currents and falls again in the form of various precipitation on the surface of the Earth, thus completing a constant water cycle

To quantify the content of water vapor in the atmosphere, various characteristics of air humidity are used.

Elasticity (actual) of water vapor (e) - the pressure of water vapor in the atmosphere is expressed in mmHg. or in millibars (mb). Numerically, it almost coincides with absolute humidity (the content of water vapor in the air in g/m3), which is why elasticity is often called absolute humidity.

Saturation elasticity (maximum elasticity) (E) is the limit of water vapor content in the air at a given temperature. The value of saturation elasticity depends on the air temperature; the higher the temperature, the more water vapor it can contain.

There are other important characteristics of humidity, such as humidity deficit and dew point.

Moisture deficit (D) – the difference between saturation elasticity and actual elasticity:

Absolute humidity. The amount of water vapor that is currently in the air is called absolute humidity. Absolute humidity is expressed in grams per 1 m 3 air or in pressure units: millimeters and millibars. The main factor influencing the distribution of absolute humidity is temperature. However, this dependence is somewhat violated by the distribution of land and water on the earth's surface, the presence of mountains, plateaus and other factors. Thus, in coastal countries, absolute humidity is usually higher than inland. However, temperature still plays a dominant role, as can be seen in the following examples.

Along with annual, monthly and daily temperature fluctuations, absolute air humidity also fluctuates. The amplitude of annual fluctuations in absolute humidity in the tropical zone is 2-3, in the temperate zone 5-6, and within the continents 9-10 mm.

Absolute humidity decreases with altitude. From observations of 74 balloon ascents in Europe, it was established that the average annual absolute humidity at the earth's surface is 6.66 mm; at an altitude of 500 m - 6,09 mm; 1 thousand m - 4,77 mm; 2 thousand m - 2.62 mm; 5 thousand m- 0,52 mm; 10 thousand m- 0,02 mm.

If saturated air is heated, it again moves away from saturation and again acquires the ability to perceive a new amount of water vapor. On the contrary, if saturated air is cooled, then it oversaturated, and under these conditions it begins condensation, i.e., condensation of excess water vapor. If you cool air that is not saturated with water vapor, it will gradually approach saturation. The temperature at which a given unsaturated air becomes saturated is called DEW POINT. If air that has cooled to its dew point (τ) cools further, it also begins to release excess water vapor through condensation. It is clear that the position of the dew point depends on the degree of air humidity. The more humid the air, the sooner the dew point will reach, and vice versa.

From all that has been said, it is clear that the ability of air to perceive and contain various maximum amounts of water vapor is directly dependent on temperature.

If the air contains less water vapor than is needed to saturate it at a given temperature, you can determine how close the air is to the saturation state. To do this, calculate relative humidity.

Relative humidity (r) is the ratio of the actual water vapor pressure to the saturation pressure, expressed as a percentage:

At saturation e = E, r = 100%.

if the relative humidity is close to 100%, then precipitation becomes very likely; at low relative humidity, on the contrary, precipitation will be unlikely.

It is not difficult to understand that the relationship between relative humidity and air temperature will be largely inverse. The higher the temperature, the further the air is from saturation, and therefore its relative humidity will be lower. Thus, V In polar countries, where low temperatures prevail, relative humidity may be the highest, while in tropical countries it may be lower. Low relative humidity is observed in subtropical latitudes, especially on land, the lowest in deserts, where the average annual relative humidity is less than 30%. In addition to temperature, relative humidity is greatly influenced by other factors. Therefore, there is no close relationship that we observed between absolute humidity and temperature.

The annual variation of relative humidity is also the inverse of the annual variation of temperature. Inside the continents at our latitudes, relative humidity is highest in winter and lowest in summer and spring.

Various hygrometers and psychrometers are used to measure air humidity. The most widely used hpix are: weight hygrometer, hair hygrometer, hygrograph and Assmann psychrometer.

Geographical distribution of humidity:

The maximum air humidity on land is observed in the area of equatorial forests.
Air humidity, like temperature, decreases with latitude. In addition, in winter it, like the temperature, is lower on the continents and higher on the oceans, therefore in winter the isolines of vapor pressure or absolute humidity, like isotherms, are bent over the continents towards the equator. There is even an area of particularly low vapor pressure with closed contours over the very cold interior of Central and East Asia.
However, in summer the correspondence between temperature and vapor content is less. Temperatures inside the continents are high in summer, but actual evaporation is limited by moisture reserves, so no more water vapor can enter the air than over the oceans, and in fact less of it enters. Consequently, the vapor pressure over the continents is not increased in comparison with the oceans, despite the higher temperature. Therefore, unlike isotherms, vapor pressure isolines in summer do not curve over the continents to high latitudes, but pass close to latitudinal circles. And deserts, such as the Sahara or the deserts of Central and Central Asia, are areas of low vapor pressure with closed contours.
In continental areas where air transport from the ocean predominates all year round, for example in Western Europe, the vapor content is quite high, close to the oceanic level in both winter and summer. In monsoon regions, such as south and east Asia, where air currents are directed from the sea in summer and from land in winter, the steam content is high in summer and low in winter.
Relative humidity is always high in the equatorial zone, where the vapor content in the air is very high and the temperature is not too high due to heavy cloud cover. Relative humidity is always high in the Arctic Ocean, in the north of the Atlantic and Pacific oceans, in Antarctic waters, where it reaches the same or almost the same high values as in the equatorial zone. However, the reason for the high relative humidity here is different. The air vapor content in high latitudes is insignificant, but the air temperature is also low, especially in winter. Similar conditions are observed in winter over the cold continents of the middle and high latitudes.
Very low relative humidity (up to 50% and below) is observed all year round in subtropical and tropical deserts, where at high temperatures the air contains little vapor.

HYDROMETEORS

precipitation released directly from the air on the earth's surface and on objects (dew, frost, frost, etc.).

1. Hydrometeors are many small droplets of water or ice falling from the atmosphere, formed on ground objects, lifted by the wind into the air from the surface of the Earth.

Precipitation may be continuous, drizzle or torrential.

Continuous precipitation can be characterized as monotonous precipitation. The duration of continuous loss can range from an hour to several days. The cause is nimbostratus and altostratus clouds with overcast skies. By the way, if the temperature is below minus ten degrees, light snow may fall under partly cloudy skies (rain, freezing rain, freezing rain, snow, sleet).

Rain is condensation of water vapor falling onto a surface in the form of water droplets. The diameter of such droplets ranges from 0.4 to 6 millimeters.

Freezing rain is ordinary raindrops, but falling when the air temperature is below zero degrees. When they come into contact with objects, these water droplets instantly freeze and turn into ice.

Freezing rain is drops of water in an ice shell with a diameter of one to three millimeters. When it hits objects, the shell is destroyed, water flows out and turns into ice. This is how ice forms.

Snow is frozen drops of water. They fall in the form of snowflakes (snow crystals) or snow flakes.

Rain and snow is a mixture of raindrops and snowflakes.

Drizzling precipitation has low intensity, but is characterized by monotony (drizzle, freezing drizzle, snow grains). Usually start and end gradually. The duration of such precipitation ranges from several hours to several days. The cause of the fall is stratus clouds or fog with continuous or significant cloudiness. Associated phenomena: haze, fog.

Drizzle is very small droplets of water having a diameter of less than 0.5 mm. When drizzle hits the surface of the water, it does not form radiating circles.

Supercooled drizzle is ordinary drizzle, but it falls when the air temperature is below zero degrees. Upon contact with objects, the drizzle instantly freezes and turns into ice.

Snow grains are frozen droplets of water less than two millimeters in diameter. They look like white grains, grains or sticks.

Rainfall begins and ends suddenly. During precipitation, the intensity of precipitation changes. Duration ranges from several minutes to two hours (shower rain, shower snow, sleet, snow pellets, ice pellets, hail). An accompanying phenomenon is strong winds and often thunderstorms. The cause of the fall is cumulonimbus clouds. Cloud cover can be both significant and light.

Shower rain is an ordinary downpour.

Shower snow – a characteristic feature is snow charges lasting from several minutes to half an hour. Visibility varies from 10 kilometers to 100 meters.

Shower rain and snow is a mixture of raindrops and snowflakes that have a torrential character.

Snow pellets are a shower of white, fragile grains with a diameter of up to 5 millimeters.

Ice pellets are the rainfall of hard grains of ice with a diameter of one to three millimeters. Sometimes grains of ice are covered with a film of water. When the air temperature is below zero degrees, the grains freeze and ice forms.

Hail is the fall of solid precipitation at air temperatures above ten degrees. Pieces of ice have different shapes and sizes. The average diameter of hailstones is from two to five millimeters, but it can also be much larger. Each hailstone consists of several layers of ice. The duration of such precipitation ranges from one to twenty minutes. Very often, hail is accompanied by rain and thunderstorms, which is typical for the nature of the middle Volga.

6. Clouds and cloudiness. Types of precipitation and types of annual precipitation.

The main reason for the formation of clouds is the upward movement of air; with such movement of air, the air cools adiabatically and water vapor condenses. All clouds, according to the nature of their structure and the altitude at which they form, are divided into 4 families, 10 main genera of clouds. 1st family: upper level clouds, lower boundary 6000m. In this family there are cirrus, cirrocumulus, cirrostratus clouds; 2 family: middle-tier clouds, lower limit 2 km; lower-tier clouds from 2000 - at the earth's surface (stratocumulus, stratus, nimbostratus); Clouds of vertical development , upper limit is the level limit of cirrus clouds, lower is 500m (cumulus, cumulonimbus). The upper level clouds are usually icy. They are thin, transparent, light, without shadows, white, the sun shines through. Clouds of the middle and lower tier, usually water, mixed, denser than cirrus, they can cause colored crowns around the sun and moon due to the diffraction of light and water droplets. The clouds of the lower tier consist of tiny drops of water and snowflakes. Clouds of vertical development are formed by ascending air currents. Convection clouds have a diurnal cycle. Vertical clouds form more often on the plains. Cloudiness - the degree of cloud coverage of the sky or the total number of clouds in the sky. Cloudiness is determined by eye using scores that express how many tens of shares of the sky are covered with clouds. Mark 1, 2, 3, points that 0.1, 0.2, 0.3 of the sky is covered with clouds. On the surface of the globe, cloudiness is distributed unevenly; in the equatorial belt it is high throughout the year. Towards the tropics it decreases, reaching its lowest value between 20-30°C, where deserts are widely distributed. Further to high latitudes it increases, reaching the highest values of 70-80°C, and towards the poles it decreases again due to a decrease in the amount of water vapor. The greatest cloudiness is located in the northern part of the Atlantic Ocean and the Arctic, where the average value is 71-81%, and in Antarctica up to 86%.

Atmospheric precipitation is moisture that falls to the surface from the atmosphere in the form of rain, drizzle, cereals, snow, and hail. Precipitation falls from clouds, but not every cloud produces precipitation. The formation of precipitation from a cloud occurs due to the enlargement of droplets to a size capable of overcoming rising currents and air resistance. The enlargement of droplets occurs due to the merging of droplets, evaporation of moisture from the surface of droplets (crystals) and condensation water vapor on others.

Forms of precipitation:

1.rain – has drops ranging in size from 0.5 to 7 mm (average 1.5 mm);

2. drizzle – consists of small drops up to 0.5 mm in size;

3.snow – consists of hexagonal ice crystals formed during the process of sublimation;

4. snow pellets - rounded nucleoli with a diameter of 1 mm or more, observed at temperatures close to zero. The grains are easily compressed with your fingers;

5. ice groats - the kernels of the groats have an icy surface, they are difficult to crush with your fingers, and when they fall to the ground they jump;

6.grad – large rounded pieces of ice ranging in size from a pea to 5-8 cm in diameter. The weight of hailstones in some cases exceeds 300 g, sometimes reaching several kilograms. Hail falls from cumulonimbus clouds.

Types of precipitation:

1. Cover precipitation - uniform, long-lasting, falls from nimbostratus clouds;

2. Rainfall – characterized by rapid changes in intensity and short duration. They fall from cumulonimbus clouds as rain, often with hail.

3. Drizzle – falls in the form of drizzle from stratus and stratocumulus clouds.

The daily variation of precipitation coincides with the daily variation of cloudiness. There are two types of daily variation of precipitation - continental and marine (coastal). The continental type has two maximums (in the morning and afternoon) and two minimums (at night and before noon). Marine type - one maximum (at night) and one minimum (daytime).

The annual course of precipitation varies at different latitudes and even within the same zone. It depends on the amount of heat, thermal conditions, air circulation, distance from the coasts, and the nature of the relief.

The most abundant precipitation is in equatorial latitudes, where the annual amount (GKO) exceeds 1000-2000 mm. On the equatorial islands of the Pacific Ocean, 4000-5000 mm falls, and on the leeward slopes of tropical islands up to 10,000 mm. Heavy precipitation is caused by powerful upward currents of very humid air. To the north and south of the equatorial latitudes, the amount of precipitation decreases, reaching a minimum of 25-35º, where the average annual value does not exceed 500 mm and decreases in inland areas to 100 mm or less. In temperate latitudes the amount of precipitation increases slightly (800 mm). At high latitudes the GKO is insignificant.

The maximum annual precipitation was recorded in Cherrapunji (India) - 26461 mm. The minimum recorded annual precipitation is in Aswan (Egypt), Iquique (Chile), where in some years there is no precipitation at all.

As is known, the balance of humidity in nature is maintained by the cycle of water evaporation and precipitation. Areas that receive little rain or snow throughout the year are considered dry, while areas that experience heavy, frequent rainfall may even suffer from excess moisture levels.

But in order for the assessment of moisture to be sufficiently objective, geographers and meteorologists use a special indicator - the moisture coefficient.

What is humidification factor?

The degree of moisture in any area depends on two indicators:

— the number of people lost per year;

— the amount of moisture evaporated from the soil surface.

In fact, the humidity of zones with a cool climate, where evaporation occurs slowly due to low temperatures, can be higher than the humidity of an area located in a hot climate zone, with the same amount of precipitation falling per year.

How is the moisture coefficient determined?

The formula by which the moisture coefficient is calculated is quite simple: the annual amount of precipitation must be divided by the annual amount of moisture evaporation. If the result of division is less than one, it means that the area is not sufficiently moistened.

When the moisture coefficient is equal to or close to unity, the moisture level is considered sufficient. For humid climatic zones, the humidity coefficient significantly exceeds unity.

Different countries use different methods for determining the moisture coefficient. The main difficulty lies in objectively determining the amount of moisture evaporated per year. In Russia and the CIS countries, since the times of the Soviet Union, a methodology developed by the outstanding Soviet soil scientist G.N. Vysotsky has been adopted.

It is highly accurate and objective, since it takes into account not the actual level of moisture evaporation, which cannot be more than the amount of precipitation, but the possible amount of evaporation. European and American soil scientists use the Torthwaite method, which is more complex by definition and not always objective.

Why do you need a moisture ratio?

Determining the moisture coefficient is one of the main tools for weather forecasters, soil scientists and scientists of other specialties. Based on this indicator, maps of water resources are drawn up, reclamation plans are developed - draining swampy areas, improving soils for growing crops, etc.

Meteorologists make their forecasts taking into account many indicators, including the humidity coefficient.

It is important to know that humidity depends not only on air temperature, but also on altitude above sea level. As a rule, mountainous areas are characterized by high values of the coefficient, since it always falls there than on the plains.

It is not surprising that many small and sometimes quite large rivers originate in the mountains. For areas located at an altitude of 1000-1200 meters above sea level or higher, the humidity coefficient often reaches 1.8 - 2.4. Excess moisture flows down in the form of mountain rivers and streams, bringing additional moisture to drier valleys.

Under natural conditions, the value of the moisture coefficient corresponds to the terrain and the availability of water resources. In zones of sufficient moisture, large and small rivers flow, there are lakes and streams. Excessive moisture often results in swamps that need to be drained.

In areas of insufficient moisture, reservoirs are rare, since the soil releases all the moisture that falls on it into the atmosphere.