Recently in different parts globe Problems related to the amount and nature of precipitation are increasingly arising. This year Ukraine experienced a very snowy winter, but at the same time Australia experienced an unprecedented drought. How does precipitation occur? What determines the nature of the loss and many other questions are relevant and important today. Therefore, I chose the topic of my work “Formation and types of precipitation.”

Thus, main goal This work is a study of the formation and types of precipitation.

During the work, the following tasks are highlighted:

• · Definition of precipitation
• · Study of existing types of precipitation
• · Consideration of the problem and consequences of acid rain.

The main research method in this work is the method of research and analysis of literary sources.

Precipitation(Greek atmos - steam and Russian to precipitate - fall to the ground) - water in liquid (drizzle, rain) and solid (cereals, snow, hail) form, falling from clouds as a result of condensation of vapors rising mainly from oceans and seas (evaporated water from land makes up about 10% of atmospheric precipitation). Atmospheric precipitation also includes frost, hoarfrost, and dew, which are deposited on the surface of ground objects when vapor condenses in moisture-saturated air. Atmospheric precipitation is a link in the Earth's overall moisture cycle. When a warm front approaches, continuous and drizzle rains are common, and when a cold front approaches, showers are common. Atmospheric precipitation is measured using a precipitation gauge on weather stations thickness of the water layer (in mm) that fell per day, month, year. The average amount of precipitation on Earth is about 1000 mm/year, but in deserts it falls less than 100 and even 50 mm/year, and in equatorial zone and on some windward mountain slopes - up to 12,000 mm/year (Charranudja weather station at an altitude of 1,300 m). Atmospheric precipitation is the main supplier of water to watercourses, into soils that feed the entire organic world.

The main condition for the formation of precipitation is the cooling of warm air, leading to condensation of the steam contained in it.

As warm air rises and cools, clouds consisting of water droplets form. Colliding in the cloud, the drops connect and their mass increases. The bottom of the cloud turns blue and it starts to rain. At subzero air temperatures, water droplets in clouds freeze and turn into snowflakes. Snowflakes stick together into flakes and fall to the ground. During snowfall, they may melt a little, and then wet snow falls. It happens that air currents Frozen drops are lowered and raised repeatedly, at which time ice layers grow on them. Finally the drops become so heavy that they fall to the ground like hail. Sometimes hailstones reach the size chicken egg. IN summer time at clear weather The earth's surface cools. It cools the ground layers of air. Water vapor begins to condense on cold objects - leaves, grass, stones. This is how dew is formed. If the surface temperature was negative, then the water droplets freeze, forming frost. Dew usually falls in summer, frost - in spring and autumn. At the same time, both dew and frost can form only in clear weather. If the sky is covered with clouds, then the earth's surface cools slightly and cannot cool the air.

According to the method of formation, convective, frontal and orographic precipitation are distinguished. The general condition for the formation of precipitation is the upward movement of air and its cooling. In the first case, the reason for the rise of air is its heating from warm surface(convection). Such precipitation falls all year round in the hot zone and in the summer in temperate latitudes. If warm air rises when interacting with colder air, frontal precipitation forms. They are more characteristic of temperate and cold zones, where warm and cold are more common air masses. The reason for the rise of warm air may be its collision with mountains. In this case, orographic precipitation is formed. They are typical for the windward slopes of mountains, and the amount of precipitation on the slopes is greater than in the adjacent areas of the plains.

The amount of precipitation is measured in millimeters. On average, about 1100 mm of precipitation falls on the earth's surface per year.

Precipitation falling from clouds: rain, drizzle, hail, snow, pellets.

There are:

• · heavy precipitation associated mainly with warm fronts;
• · rainfall associated with cold fronts. Precipitation deposited from the air: dew, frost, frost, ice. Precipitation is measured by the thickness of the layer of fallen water in millimeters. On average, the globe receives about 1000 mm of precipitation per year, while in deserts and high latitudes it falls less than 250 mm per year.

Precipitation measurements are carried out by rain gauges, precipitation gauges, pluviographs at meteorological stations, and for large areas- with the help of radar.

Perennial, average monthly, seasonal, annual quantity precipitation, its distribution over earth's surface, annual and daily cycle, frequency, intensity are the defining characteristics of climate that are essential for Agriculture and many other sectors of the national economy.

The greatest amount of precipitation on the globe should be expected where there is great atmospheric humidity and where conditions exist for rising and cooling air. The amount of precipitation depends: 1) on latitude, 2) on general circulation atmosphere and related processes, 3) from relief.

The greatest amount of precipitation both on land and at sea falls near the equator, in the zone between 10° N. w. and 10° S. w. Further north and south, precipitation decreases in the trade wind region, with precipitation minimums more or less coinciding with subtropical pressure maximums. At sea, precipitation minimums are located closer to the equator than on land. However, the figures illustrating the amount of precipitation at sea cannot be particularly trusted due to the insignificant number of observations.

From subtropical pressure maxima and precipitation minima, the amount of these latter increases again and reaches a second maximum at approximately latitudes of 40-50°, and from here it decreases towards the poles.

The large amount of precipitation under the equator is explained by the fact that here, due to thermal reasons, an area is created low blood pressure with rising currents, air with a high content of water vapor (on average e = 25 mm), rising, cools and condenses moisture. The low amount of precipitation in the trade wind region is due to these latter winds.

The lowest amount of precipitation observed in the area of ​​subtropical pressure maxima is explained by the fact that these areas are characterized by downward air movement. As the air descends, it heats up and becomes dry. Further north and south we enter an area of ​​predominantly southwestern and northwest winds, i.e. winds moving from more warm countries in colder ones. Here, in addition, cyclones very often arise, therefore, conditions are created that are favorable for the rise of air and its cooling. All this entails an increase in precipitation.

As for the decrease in precipitation in the polar region, it must be borne in mind that it relates only to measured precipitation - rain, snow, graupel, but the deposition of frost is not taken into account; Meanwhile, it must be assumed that the formation of frost in polar countries, where due to low temperature relative humidity very large, occurs in large quantities. Indeed, some polar travelers observed that condensation occurs here mainly from the lower layers of air in contact with the surface in the form of frost or ice needles, settling on the surface of snow and ice and noticeably increasing their thickness.

Relief has a huge impact on the amount of moisture that falls. Mountains, forcing the air to rise, cause it to cool and condense vapors.

It is especially clear to trace the dependence of the amount of precipitation on altitude in such settlements that are located on the slopes of mountains, with their lower quarters located at sea level, and their upper quarters located quite high. Indeed, in each area, depending on the totality of meteorological conditions, there is specific zone, or the height at which maximum vapor condensation occurs, and above this zone the air becomes drier. Thus, on Mont Blanc the zone of greatest condensation lies at an altitude of 2600 m, in the Himalayas on the southern slope - on average at an altitude of 2400 m, in the Pamirs and Tibet - at an altitude of 4500 m. Even in the Sahara, the mountains condense moisture.

By time of fall maximum quantity precipitation, all countries can be divided into two categories: 1) countries with predominant summer precipitation and 2) countries with predominant winter precipitation. The first category belongs tropical region, more continental regions of temperate latitudes and northern edges of the land northern hemisphere. Winter precipitation predominates in subtropical countries, then in the oceans and seas, as well as in countries with maritime climate in temperate latitudes. In winter, the oceans and seas are warmer than the land, the pressure decreases, creating favorable conditions for the occurrence of cyclones and increased precipitation. We can establish the following divisions on the globe based on the distribution of rainfall.

Types of precipitation. Hail is a special kind of ice formation that sometimes falls from the atmosphere and is classified as precipitation, otherwise known as hydrometeors. The type, structure and size of hailstones are extremely diverse. One of the most common shapes is conical or pyramidal with sharp or slightly truncated tops and a rounded base. Top part these are usually softer, matte, as if snowy; the middle one is translucent, consisting of concentric, alternating transparent and opaque layers; the bottom, widest one is transparent.

No less common is a spherical shape consisting of an inner snow core (sometimes, although less often, the central part consists of clear ice), surrounded by one or more transparent shells. The phenomenon of hail is accompanied by a special characteristic noise from the impact of hailstones, reminiscent of the noise that occurs from the spilling of nuts. Hail falls mostly in the summer and during the day. Hail at night is a very rare phenomenon. Lasts several minutes, usually less than a quarter of an hour; but there are times when it lasts longer. The distribution of hail on earth depends on latitude, but mainly on local conditions. In tropical countries, hail is a very rare phenomenon, and it falls there almost only on high plateaus and mountains.

Rain is liquid precipitation in the form of droplets with a diameter of 0.5 to 5 mm. Individual raindrops leave a mark on the surface of water in the form of a diverging circle, and on the surface of dry objects - in the form of a wet spot.

Supercooled rain is liquid precipitation in the form of drops with a diameter of 0.5 to 5 mm, falling at negative air temperatures (most often 0...-10°, sometimes up to -15°) - falling on objects, the drops freeze and ice forms. Freezing rain forms when falling snowflakes hit a layer of warm air deep enough for the snowflakes to completely melt and become raindrops. As these droplets continue to fall, they pass through a thin layer of cold air above the earth's surface and their temperature drops below freezing. However, the droplets themselves do not freeze, so this phenomenon is called supercooling (or the formation of “supercooled droplets”).

Freezing rain is solid precipitation that falls at negative air temperatures (most often 0...-10°, sometimes up to -15°) in the form of hard transparent ice balls with a diameter of 1-3 mm. Formed when raindrops freeze as they fall through bottom layer air from negative temperature. Inside the balls there is unfrozen water - when falling on objects, the balls break into shells, the water flows out and ice forms. Snow is solid precipitation that falls (most often at negative air temperatures) in the form of snow crystals (snowflakes) or flakes. With light snow, horizontal visibility (if there are no other phenomena - haze, fog, etc.) is 4-10 km, with moderate snow 1-3 km, with heavy snow - less than 1000 m (in this case, snowfall increases gradually, so visibility values ​​of 1-2 km or less are observed no earlier than an hour after the start of snowfall). IN frosty weather(air temperature below -10...-15°) light snow may fall from a partly cloudy sky. Separately, the phenomenon of wet snow is noted - mixed precipitation that falls at positive air temperatures in the form of flakes of melting snow. Rain and snow are mixed precipitation that falls (most often at positive air temperatures) in the form of a mixture of drops and snowflakes. If rain and snow fall at subzero air temperatures, precipitation particles freeze onto objects and ice forms.

Drizzle is liquid precipitation in the form of very small drops (less than 0.5 mm in diameter), as if floating in the air. A dry surface becomes wet slowly and evenly. When deposited on the surface of the water, it does not form diverging circles on it.

Fog is a collection of condensation products (droplets or crystals, or both) suspended in the air directly above the surface of the earth. Cloudiness of the air caused by such accumulation. Usually these two meanings of the word fog are not distinguished. In fog, horizontal visibility is less than 1 km. Otherwise, the cloudiness is called haze.

Rainfall is short-term precipitation, usually in the form of rain (sometimes wet snow, cereals), characterized by high intensity (up to 100 mm/h). Occurs in unstable air masses on a cold front or as a result of convection. Typically, torrential rain covers a relatively small area. Shower snow is snow of a shower nature. Characterized by sharp fluctuations in horizontal visibility from 6-10 km to 2-4 km (and sometimes up to 500-1000 m, in some cases even 100-200 m) over a period of time from several minutes to half an hour (snow “charges”) . Snow pellets are solid rainfall precipitation that falls at an air temperature of about zero degrees and has the appearance of opaque white grains with a diameter of 2-5 mm; The grains are fragile and easily crushed by fingers. Often falls before or simultaneously with heavy snow. Ice grains are solid rainfall precipitation that falls at air temperatures from +5 to +10° in the form of transparent (or translucent) ice grains with a diameter of 1-3 mm; in the center of the grains there is an opaque core. The grains are quite hard (they can be crushed with your fingers with some effort), and when they fall on a hard surface they bounce off. In some cases, the grains may be covered with a film of water (or fall out along with droplets of water), and if the air temperature is below zero, then falling on objects, the grains freeze and ice forms.

Dew (Latin ros - moisture, liquid) is atmospheric precipitation in the form of water droplets deposited on the surface of the earth and ground objects when the air cools.

Frost is loose ice crystals that grow on tree branches, wires and other objects, usually when drops of supercooled fog freeze. It is formed in winter, more often in calm frosty weather as a result of sublimation of water vapor when the air temperature drops.

Frost is a thin layer of ice crystals that forms on cold, clear and quiet nights on the surface of the earth, grass and objects with a negative temperature, lower than the air temperature. Frost crystals, like frost crystals, are formed by sublimation of water vapor.

Acid rain was first noted in Western Europe, in particular Scandinavia, and North America in the 1950s Now this problem exists throughout the industrial world and has acquired particular significance in connection with increased man-made emissions of sulfur and nitrogen oxides. precipitation acid rain

When power plants and industrial enterprises burn coal and oil, with their chimneys are thrown away huge quantities sulfur dioxide, suspended particles and nitrogen oxides. In the United States, power plants and factories account for 90 to 95% of sulfur dioxide emissions. and 57% nitrogen oxides, with almost 60% of sulfur dioxide emitted by tall pipes, making them easier to transport over long distances.

As discharges of sulfur dioxide and nitrogen oxide from stationary sources are carried over long distances by wind, they produce secondary pollutants such as nitrogen dioxide, nitric acid vapor, and droplets containing solutions of sulfuric acid, sulfate and nitrate salts. These chemical substances fall on the earth's surface in the form of acid rain or snow, and also in the form of gases, veils, dew or solid particles. These gases can be directly absorbed by the foliage. The combination of dry and wet precipitation and the absorption of acids and acid-forming substances from or on the earth's surface is called acid precipitation or acid rain. Another reason acid precipitation are nitrogen oxide emissions large numbers cars in major cities. This type of pollution poses a danger to both urban and rural areas. After all, drops of water and most solid particles are quickly removed from the atmosphere, acid precipitation are more of a regional or continental problem than a global one.

Consequences of acid rain:

• · Damage to statues, buildings, metals and vehicle trim.
• Loss of fish aquatic plants and microorganisms in lakes and rivers.
• · Weakening or loss of trees, especially coniferous species that grow at high altitudes due to leaching of calcium, sodium and other nutrients from the soil Damage to tree roots and loss of numerous types fish due to the release of aluminum, lead, mercury and cadmium ions from soils and milk sediments
• · Weakening of trees and increasing their susceptibility to diseases, insects, droughts, fungi and mosses that bloom in an acidic environment.
• · Slow growth cultivated plants, such as tomatoes, soybeans, beans, tobacco, spinach, carrots, broccoli and cotton.

Acid precipitation is already a serious problem in northern and central Europe, the northeastern United States, southeastern Canada, parts of China, Brazil and Nigeria. They are beginning to pose an increasing threat in the industrial regions of Asia, Latin America and Africa and in some places in the western United States (mainly due to dry precipitation). Acid precipitation also occurs in tropical regions where industry is practically undeveloped, mainly due to the release of nitrogen oxides during the combustion of biomass. Most of the acid-forming substances produced water country, be transported by prevailing surface winds to the territory of another. More than three-quarters of the acid rain in Norway, Switzerland, Austria, Sweden, the Netherlands and Finland is blown into these countries by wind from the industrial areas of Western and Eastern Europe.

List of used literature

• 1. Akimova, T. A., Kuzmin A. P., Khaskin V. V., Ecology. Nature - Man - Technology: Textbook for universities. - M.: UNITY - DANA, 2001. - 343 p.
• 2. Vronsky, V. A. Acid rain: environmental aspect//Biology at school.- 2006.- No. 3.- p. 3-6
• 3. Isaev, A. A. Ecological climatology. - 2nd ed. corr. and additional - M.: Scientific world, 2003.- 470 p.
• 5. Nikolaikin, N. I., Nikolaikina N. E., Melekhova O. P. ecology. - 3rd ed. reworked and additional - M.: Bustard, 2004.- 624 p.
• 6. Novikov, Yu. V. Ecology, environment, person: Textbook.- M.: Grand: Fair - press, 2000.- 316 p.

Atmospheric precipitation is moisture that falls to the surface from the atmosphere in the form of rain, drizzle, cereals, snow, and hail. Precipitation comes from clouds, but not every cloud produces precipitation. Formation of precipitation from clouds are coming due to the enlargement of droplets to sizes 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 of 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 pellets - 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. hail - 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– fall as drizzle from stratus and stratocumulus clouds.

Distribution of annual precipitation (mm) (according to S.G. Lyubushkin and others)

(lines on a map connecting points with the same amount of precipitation over a certain period of time (for example, a year) are called isohyets)

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 heaviest precipitation is in equatorial latitudes ah, where their annual quantity (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.

Distribution of precipitation across continents as a percentage of the total

				Australia		Northern
Below 500 mm
500 –1000 mm
Over 1000 mm

By origin There are convective, frontal and orographic precipitation.

1. Convective precipitation are typical for the hot zone, where heating and evaporation are intense, but in summer they often occur in the temperate zone.
2. Frontal precipitation are formed when two air masses meet different temperatures and others physical properties, fall from warmer air that forms cyclonic vortices, typical of temperate and cold zones.
3. Orographic precipitation fall on the windward slopes of mountains, especially high ones. They are abundant if the air comes from the side warm sea and has high absolute and relative humidity.

Types of precipitation by origin:

I - convective, II - frontal, III - orographic; TV - warm air, HV - cold air.

Annual course of precipitation, i.e. the change in their number by month and in different places on Earth is not the same. Several basic types can be identified annual progress precipitation and express them in the form of bar graphs.

1. Equatorial type – precipitation falls fairly evenly throughout the year, there are no dry months, only after the days of the equinox two small maximums are noted - in April and October - and after the days of the solstice two small minimums are noted - in July and January.
2. Monsoon type – maximum precipitation in summer, minimum in winter. Characteristic of subequatorial latitudes, as well as east coasts continents in subtropical and temperate latitudes. The total amount of precipitation gradually decreases from the subequatorial to the temperate zone.
3. Mediterranean type – maximum precipitation in winter, minimum in summer. It is observed in subtropical latitudes on the western coasts and inland. Annual precipitation gradually decreases towards the center of the continents.
4. Continental type of precipitation of temperate latitudes – in the warm period there is two to three times more precipitation than in the cold period. As the climate becomes more continental in the central regions of the continents total precipitation decreases, and the difference between summer and winter precipitation increases.
5. Marine type of temperate latitudes – precipitation is distributed evenly throughout the year with a slight maximum in autumn-winter. Their number is greater than observed for this type.

Types of annual precipitation:

1 - equatorial, 2 - monsoon, 3 - Mediterranean, 4 - continental temperate latitudes, 5 - maritime temperate latitudes.

Literature

1. Zubaschenko E.M. Regional Physiography. Earth's climates: teaching aid. Part 1. / E.M. Zubaschenko, V.I. Shmykov, A.Ya. Nemykin, N.V. Polyakova. – Voronezh: VSPU, 2007. – 183 p.

Precipitation- water in a liquid or solid state that falls from clouds or settles from the air onto the earth's surface.

Rain

Under certain conditions, cloud droplets begin to merge into larger and heavier ones. They can no longer stay in the atmosphere and fall to the ground in the form rain.

hail

It happens that in the summer the air quickly rises and picks up rain clouds and carries them to a height where the temperature is below 0°. Raindrops freeze and fall as hail(Fig. 1).

Rice. 1. Origin of the hail

Snow

In winter, in temperate and high latitudes, precipitation falls in the form of snow. Clouds at this time do not consist of water droplets, but of tiny crystals - needles, which, joining together, form snowflakes.

Dew and frost

Precipitation falling onto the earth's surface not only from clouds, but also directly from the air is dew And frost.

The amount of precipitation is measured by a precipitation gauge or rain gauge (Fig. 2).

Rice. 2. Structure of the rain gauge: 1 - outer casing; 2 - funnel; 3 - container for collecting oxen; 4-dimensional tank

Classification and types of precipitation

Precipitation is distinguished by the nature of precipitation, by origin, by physical state, by seasons of precipitation, etc. (Fig. 3).

According to the nature of precipitation, precipitation can be torrential, heavy and drizzling. Rainfall - intense, short-lived, cover a small area. Cover precipitation - medium intensity, uniform, long-term (can last for days, capturing large areas). Drizzle - fine precipitation falling over a small area.

Precipitation is classified according to its origin:

• convective - characteristic of the hot zone, where heating and evaporation are intense, but often occur in the temperate zone;
• frontal - are formed when two air masses with different temperatures meet and fall out of the warmer air. Characteristic for temperate and cold zones;
• orographic - fall on the windward slopes of the mountains. They are very abundant if the air comes from the warm sea and has high absolute and relative humidity.

Rice. 3. Types of precipitation

Comparing to climate map the annual amount of precipitation in the Amazonian lowland and the Sahara Desert, one can be convinced of its uneven distribution (Fig. 4). What explains this?

Precipitation comes from moist air masses that form over the ocean. This is clearly seen in the example of territories with monsoon climate. The summer monsoon brings a lot of moisture from the ocean. And there are continuous rains over the land, as on the Pacific coast of Eurasia.

Constant winds also play a big role in the distribution of precipitation. Thus, trade winds blowing from the continent bring dry air to northern Africa, where the most vast desert world - Sahara. Western winds bring rain from the Atlantic Ocean to Europe.

Rice. 4. Average annual distribution of precipitation on Earth's land

As you already know, sea currents affect precipitation in the coastal parts of continents: warm currents contribute to their appearance (the Mozambique Current off the eastern coast of Africa, the Gulf Stream off the coast of Europe), cold weather, on the contrary, prevents precipitation ( Peruvian Current off the western coast of South America).

Relief also affects the distribution of precipitation, for example, the Himalayan mountains do not allow moist winds blowing from the north to pass through. Indian Ocean. Therefore, on their southern slopes sometimes up to 20,000 mm of precipitation falls per year. Moist air masses, rising along the mountain slopes (ascending air currents), cool, become saturated, and precipitation falls from them. The territory north of the Himalayan mountains resembles a desert: only 200 mm of precipitation falls there per year.

There is a relationship between belts and precipitation. At the equator - in the belt low pressure— constantly heated air; rising upward, it cools and becomes saturated. Therefore, in the equator region there are many clouds and heavy rainfall. A lot of precipitation also falls in other areas of the globe where low pressure prevails. At the same time, air temperature is of great importance: the lower it is, the less precipitation falls.

In belts high pressure downward air currents predominate. As the air descends, it heats up and loses the properties of its saturation state. Therefore, at latitudes 25-30° precipitation occurs rarely and in small quantities. Areas of high pressure near the poles also receive little precipitation.

Absolute maximum precipitation registered on o. Hawaii (Pacific Ocean) - 11,684 mm/year and in Cherrapunji (India) - 11,600 mm/year. The absolute minimum - in the Atacama Desert and the Libyan Desert - less than 50 mm/year; Sometimes there is no precipitation at all for years.

The moisture content of the area is characterized by humidification coefficient— the ratio of annual precipitation and evaporation for the same period. The humidification coefficient is denoted by the letter K, the annual amount of precipitation by the letter O, and evaporation by the letter I; then K = O: I.

The lower the humidification coefficient, the drier the climate. If the annual precipitation is approximately equal to evaporation, then the humidification coefficient is close to unity. In this case, hydration is considered sufficient. If the moisture level more than one, then hydration excessive, less than one - insufficient. When the humidification coefficient is less than 0.3, humidification is considered meager. Zones with sufficient moisture include forest-steppes and steppes, and zones with insufficient moisture include deserts.

SEDIMENTS, THEIR FORMS AND TYPES. INFLUENCE OF PRECIPITATION ON THE FIELD

Precipitation called drops of water and ice crystals falling from clouds or settling from the air onto the earth's surface. Precipitation from clouds provides more than 99% of the total amount of water coming from the atmosphere to the earth's surface; less than 1% comes from precipitation deposited from the air.

Precipitation x is characterized by quantity and intensity. Precipitation measured by the thickness (expressed in mm or cm) of the layer of water that it would form on the surface of the earth in the absence of infiltration, runoff and evaporation. Intensity − this is the amount of precipitation falling per unit of time (per minute or hour).

A necessary condition For the formation of precipitation is the enlargement of cloud elements to such sizes at which the speed of falling of these elements becomes greater than the speed of ascending flows. The consolidation process occurs mainly for the following reasons:

a) due to the recondensation of water from steam from water droplets onto ice crystals or from

small drops to large ones. This happens because the saturation elasticity over ice crystals is less than over water droplets, and over large drops it is less than over small ones.

b) due to the merging (coagulation) of water droplets upon their collision as a result of turbulent air movements and different speed falling of large and small drops. These collisions lead to the absorption of small droplets by large ones.

The growth of droplets due to condensation predominates until the radius of the droplet becomes equal to 20...60 μm, after which the main process of enlargement of cloud elements becomes coagulation.

Clouds that are homogeneous in structure, i.e. consisting only of identical

the size of droplets or only from ice crystals, precipitation is not given. Such clouds include cumulus and altocumulus, consisting of small water droplets, as well as cirrus, cirrocumulus and cirrostratus, consisting of ice crystals.

In clouds made of drops different sizes, there is a slow growth of larger droplets at the expense of small ones. However, as a result of this process, only small drops of rain are formed. This process occurs in stratus and sometimes in stratocumulus clouds, from which precipitation can fall in the form of drizzle.

c) the main types of precipitation fall from mixed clouds, in which the enlargement of cloud elements occurs due to the freezing of supercooled drops on ice crystals. The consolidation of cloud elements proceeds rapidly and is accompanied by rain or snow. These clouds include cumulonimbus, nimbostratus and altostratus.

Precipitation falling from clouds can be liquid, solid or mixed.

Main forms of precipitation are:

Drizzle – tiny droplets of water with a diameter of less than 0.5 mm, practically suspended in the air. Their fall is almost invisible to the eye. When there are a lot of drops, the drizzle becomes like fog. However, unlike fog, drops of drizzle fall onto the earth's surface.

Wet snow– precipitation consisting of melting snow at a temperature of – 0°…+5°С.

Snow pellets– soft milky-white opaque grains of round shape with a diameter of 2...5 mm.

Ice grains – transparent grains with a dense white core in the center. The diameter of the grains is less than 5 mm. It is formed when raindrops or partially melted snowflakes freeze when falling through the lower layer of air with a negative temperature.

hail– precipitation in the form of ice pieces of various sizes. Hailstones have an irregular or spherical (close to spherical) shape, their size ranges from 5 mm to 10 cm or more. Therefore, the weight of hailstones can be very large. In the center of the hailstones there is a whitish translucent grain, surrounded by several layers of transparent and opaque ice.

freezing rain– small transparent spherical particles with a diameter of 1...3 mm. They are formed when raindrops freeze, falling through the lower layer of air with a negative temperature (rain at a temperature of 0°... 5°C).

Ice needles - tiny ice crystals that do not have a branchy structure, like snowflakes. Observed in quiet frosty weather. Visible as sparkling in sun rays sparkles.

By the nature of the loss, depending on physical educational conditions,

duration and intensity, precipitation is divided into three types:

1. Cover precipitation − these are long-lasting, medium-intensity precipitation in the form of raindrops or snow flakes, which are observed simultaneously over a large area. This precipitation falls from a system of frontal nimbostratus and altostratus clouds.

2. Rainfall − these are short-term, high intensity precipitation in the form of large drops, large snow flakes, sometimes ice pellets or hail, which are usually observed over small areas. They fall out of cumulonimbus, and sometimes powerful cumulus (in the tropics) clouds. They usually begin suddenly and do not last long, but in some cases they can recur several times. Rainfall is often accompanied by thunderstorms and squalls.

3. Drizzle − very small drops, tiny snowflakes or snow grains, settling from clouds to the ground almost imperceptibly to the eye. Observed simultaneously over a large area, their intensity is very low and is usually determined not by the amount of precipitation, but by the degree of deterioration in horizontal visibility. They fall from stratus and stratocumulus clouds.

To precipitation released directly from the air, include: dew, frost, frost, liquid or solid deposits on the windward side of vertically located objects.

Dew- this is liquid precipitation in the form of small droplets of water formed in summer nights and in the morning on objects located near the surface of the earth, plant leaves, etc. Dew is formed when moist air comes into contact with cooled objects, as a result of which water vapor condenses.

Frost- this is a white, fine-crystalline deposit formed as a result of sublimation of water vapor in cases where the temperature of the surface air and underlying surface is below 0°C;

High moisture content, low clouds and low winds contribute to the formation of dew and frost. A layer of air with a thickness of

200...300 m and more. Frost that forms on the surface of an aircraft on the ground must be carefully removed before departure, as this can lead to serious consequences due to the fact that the aerodynamic qualities of the aircraft deteriorate.

frost- This is white, loose, snow-like ice. It forms in foggy frosty weather with very light winds on branches of trees and bushes, wires and other objects. The formation of frost is mainly associated with the freezing of tiny supercooled droplets colliding with various objects. Snowy bang Roma frost can be of the most bizarre shapes. It easily crumbles when shaken, but when the temperature rises and there is a new cold snap, it can freeze and freeze.

Liquid and solid plaque is formed on the windward part of vertically located objects cooled to a temperature below the ambient air temperature. In warm weather, a liquid coating forms, and at surface temperatures below 0°C, white translucent ice crystals form. This type of precipitation can form at any time of the day during sudden warming in the cold season.

Blowing snow is a special form of sediment transport. There are three types of blizzards:

drifting snow, blowing snow and general snowstorm.

Snowy drift And blowing snow are formed during the transfer of dry snow over the surface of the earth. Drifting snow is formed with winds of 4...6 m/s, snow rises to heights of up to 2 m above the ground. A blowing snow is formed when the wind is 6 m/s or more, the snow rises to heights of more than 2 m above the ground surface. At general snowstorm (does not have its own icon) snow is falling from the clouds, wind is 10 m/s or more, previously fallen snow is rising from the ground and visibility is less than 1000 m.

All types of precipitation complicate flight operations. The effect of precipitation on flights depends on its type, the nature of the precipitation and the air temperature.

1. During precipitation, visibility deteriorates and the cloud base decreases. In moderate rain, when flying at low speed, horizontal visibility deteriorates to 4...2 km, and at high flight speed - to 2...1 km. A significant deterioration in horizontal visibility is observed when flying in a snowfall zone. In light snow, visibility usually does not exceed 1...2 km, and in moderate and heavy snow it deteriorates to several hundred meters. In heavy rainfall, visibility sharply decreases to several tens of meters. The lower boundary of clouds in the precipitation zone, especially on atmospheric fronts, decreases to 50...100 m and can be located below the decision altitude.

2. Precipitation in the form of hail causes mechanical damage to aircraft. At high speed and flight, even small hailstones can make significant dents and destroy the cockpit glazing. Hail sometimes occurs at significant altitudes: small hail is observed at an altitude of about 13 km, and large hail is observed at an altitude of 9.5 km. The destruction of glazing at high altitudes can lead to depressurization, which is very dangerous.

3. When flying in the zone freezing rain intense icing is observed

aircraft.

4. Long-term continuous precipitation in the warm season causes waterlogging of the soil and disables unpaved airfields for some time or another, disrupting the regularity of the departure and reception of aircraft.

5. Heavy rainfall worsens the aerodynamic qualities of the aircraft, which can lead to stalling. In connection with this, landing in heavy rainfall with visibility less than 1000 m prohibited .

6. When flying along VFR in a snowfall zone over a snow-covered surface, the contrast of all objects on the earth's surface is significantly reduced and, therefore, orientation is greatly deteriorated.

7. When landing on a wet or snow-covered runway, the aircraft's flight distance increases. Slip on a runway covered with snow is 2 times greater than on a concrete runway.

8. When an aircraft takes off from a runway covered with slush, hydroplaning may occur. The wheels of the aircraft throw off powerful jets of water and slush, causing strong braking and increasing the take-off run. Conditions may arise that the aircraft will not achieve take-off speed and a dangerous situation may arise.

9. Snow that falls in winter requires additional work to remove and compact it on the runway, taxiways and parking areas where services are provided. aircraft and other machines and mechanisms.

Precipitation- water in a liquid or solid state that falls from clouds or precipitates directly from the air onto the surface of the Earth. These include:

Rain. The smallest droplets of water, with a diameter of 0.05 to 0.1 mm, that make up the clouds, merging with each other, gradually increase in size, become heavy and fall to the ground in the form of rain. The stronger the ascending jets of air from the sun-heated surface, the larger the falling drops should be. Therefore, in the summer, when the surface air is heated by the earth and rapidly rises, rain usually falls in the form of large drops, and in the spring and autumn - drizzle. If rain falls from stratus clouds, then such rain is blanket rain, and if it falls from stratus clouds, it is torrential. It is necessary to distinguish drizzle from rain. This type of precipitation usually falls from stratus clouds. The droplets are much smaller in size than raindrops. The speed of their fall is so slow that they appear suspended in the air.

Snow. It is formed when the cloud is in air with a temperature below 0°. Snow consists of crystals of various shapes. The most snow falls on the slopes of Rainier (state) - an average of 14.6 m annually. This is enough to fill a 6-story house.

hail. It occurs with strong upward air currents in the warm season. Droplets of water, falling to great heights with air currents, freeze, and ice crystals begin to grow on them in layers. The drops become heavier and begin to fall down. When falling, they increase in size from merging with drops of supercooled water. Sometimes hail reaches the size of a chicken egg, usually with varying layers of density. Typically, hail falls from powerful cumulonimbus clouds during rainfall. The frequency of hail varies: in temperate latitudes it occurs 10-15 times a year, on land, where updrafts are much more powerful, it occurs 80-160 times a year. Hail falls less frequently over the oceans. Hail brings big material damage: destroys crops, vineyards, and if the hailstones are large in size, then it can cause the destruction of houses and the death of people. In our country, methods for identifying hail clouds have been developed and hail control services have been created. Dangerous clouds are “shot” with special chemicals.

Rain, snow, and hail are called hydrometeorites. In addition to them, precipitation also includes those that are deposited directly from the air. These include dew, fog, frost, etc.

Dew(Latin ros - moisture, liquid) - precipitation in the form of water droplets deposited on the surface of the earth and ground objects when the air cools. In this case, water vapor, cooling, changes from a state to liquid and settles. Most often, dew is observed at night, in the evening or early in the morning.

Fog(turk, darkness) is an accumulation of small water drops or ice crystals in the lower part of the troposphere, usually near the surface of the earth. visibility is sometimes reduced to several meters. Fogs are distinguished by their origin into advective fogs (due to the cooling of warm moist air over a colder surface of land or water) and radiation fogs (formed as a result of cooling of the earth's surface). In a number of regions of the Earth there are often fogs on the coasts in places where cold currents pass. For example, Atacama is located on the coast. The cold Peruvian Current runs along the coast. Its cold deep waters contribute to the formation of fogs, from which drizzle settles on the coast - the only source of moisture in the Atacama Desert.