Aviation meteorology. Aviation meteorology Basics of aviation meteorology

Aviation meteorology

Aviation meteorology

(from the Greek met(éö)ra - celestial phenomena and logos - word, doctrine) - an applied discipline that studies the meteorological conditions in which aircraft operate, and the impact of these conditions on the safety and efficiency of flights, developing methods for collecting and processing meteorological information, preparation of forecasts and meteorological support for flights. As aviation develops (the creation of new types of aircraft, the expansion of the range of altitudes and flight speeds, the scale of territories for flight operations, the expansion of the range of tasks solved with the help of aircraft, etc.), aviation is faced with. new tasks are being set. The creation of new airports and the opening of new air routes requires climatic research in the areas of proposed construction and in the free atmosphere along the planned flight routes in order to select optimal solutions to the tasks. Changing conditions around existing airports (as a result of human activity or under the influence of natural physical processes) requires constant study of the climate of existing airports. Close dependence weather at the earth's surface (the take-off and landing zone of an aircraft) from local conditions requires special research for each airport and the development of methods for forecasting take-off and landing conditions for almost every airport. The main tasks of M. a. as an applied discipline - increasing the level and optimizing flight information support, improving the quality of meteorological services provided (the accuracy of actual data and the accuracy of forecasts), increasing efficiency. The solution to these problems is achieved by improving the material and technical base, technologies and observation methods, in-depth study of the physics of the formation processes of weather phenomena important for aviation and improving methods for forecasting these phenomena.

Aviation: Encyclopedia. - M.: Great Russian Encyclopedia. Editor-in-Chief G.P. Svishchev. 1994 .

See what “aviation meteorology” is in other dictionaries:

Aviation meteorology- Aviation meteorology: an applied discipline that studies the meteorological conditions of aviation, their impact on aviation, forms of meteorological support for aviation and methods of protecting it from adverse atmospheric influences...... ... Official terminology

An applied meteorological discipline that studies the influence of meteorological conditions on aviation equipment and aviation activities and develops methods and forms of its meteorological services. The main practical task of MA... ...

aviation meteorology Encyclopedia "Aviation"

aviation meteorology- (from the Greek metéōra celestial phenomena and logos word, doctrine) applied discipline that studies the meteorological conditions in which aircraft operate, and the influence of these conditions on the safety and efficiency of flights,... ... Encyclopedia "Aviation"

See Aviation meteorology... Great Soviet Encyclopedia

Meteorology- Meteorology: the science of the atmosphere about its structure, properties and physical processes occurring in it, one of the geophysical sciences (the term atmospheric sciences is also used). Note The main disciplines of meteorology are dynamic, ... ... Official terminology

The science of the atmosphere, its structure, properties and processes occurring in it. Refers to geophysical sciences. Based on physical research methods (meteorological measurements, etc.). Within meteorology there are several sections and... Geographical encyclopedia

aviation meteorology- 2.1.1 aviation meteorology: An applied discipline that studies the meteorological conditions of aviation, their impact on aviation, forms of meteorological support for aviation and methods of protecting it from adverse atmospheric influences.… … Dictionary-reference book of terms of normative and technical documentation

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Atmosphere

Composition and properties of air.

The atmosphere is a mixture of gases, water vapor and aerosols (dust, condensation products). The share of the main gases is: nitrogen 78%, oxygen 21%, argon 0.93%, carbon dioxide 0.03%, others account for less than 0.01%.

Air is characterized by the following parameters: pressure, temperature and humidity.

International standard atmosphere.

Temperature gradient.

The air is heated by the ground, and density decreases with height. The combination of these two factors creates a normal situation where air is warmer at the surface and gradually cools with height.

Humidity.

Relative humidity is measured as a percentage as the ratio of the actual amount of water vapor in the air to the maximum possible at a given temperature. Warm air can dissolve more water vapor than cold air. As the air cools, its relative humidity approaches 100% and clouds begin to form.

Cold air in winter is closer to saturation. Therefore, winter has a lower cloud base and distribution.

Water can be in three forms: solid, liquid, gas. Water has a high heat capacity. In the solid state it has a lower density than in the liquid state. As a result, it softens the climate on a planetary scale. In a gaseous state it is lighter than air. The weight of water vapor is 5/8 of the weight of dry air. As a result, moist air rises above dry air.

Atmospheric movement

Wind.

Wind arises from a pressure imbalance, usually in the horizontal plane. This imbalance appears due to differences in air temperatures in neighboring areas or vertical air circulation in different areas. The root cause is solar heating of the surface.

Wind is named by the direction from which it blows. For example: northern blows from the north, mountain blows from the mountains, valley blows into the mountains.

Coriolis effect.

The Coriolis effect is very important for understanding global processes in the atmosphere. The result of this effect is that all objects moving in the northern hemisphere tend to turn to the right, and in the southern hemisphere - to the left. The Coriolis effect is strong at the poles and disappears at the equator. The Coriolis effect is caused by the rotation of the Earth under moving objects. This is not some real force, it is an illusion of right rotation for all freely moving bodies. Rice. 32

Air masses.

An air mass is air that has the same temperature and humidity over an area of ​​at least 1600 km. An air mass can be cold if it formed in the polar regions, warm - from tropical zone. It can be marine or continental in humidity.

When a CVM arrives, the ground layer of air is heated by the ground, increasing instability. When the TBM arrives, the surface layer of air cools, descends and forms an inversion, increasing stability.

Cold and warm front.

A front is the boundary between warm and cold air masses. If cold air moves forward, it is a cold front. If warm air moves forward, it is a warm front. Sometimes air masses move until they are stopped by the increased pressure in front of them. In this case, the frontal boundary is called a stationary front.

Rice. 33 cold front warm front

Front of occlusion.

Clouds

Types of clouds.

There are only three main types of clouds. These are stratus, cumulus and cirrus i.e. stratus (St), cumulus (Cu) and cirrus (Ci).

stratus cumulus cirrus Fig. 35

Classification of clouds by height:

Rice. 36

Lesser known clouds:

Haze - Forms when warm, moist air moves ashore, or when the ground radiates heat into a cold, moist layer at night.

Cloud cap - forms above the peak when dynamic updrafts occur. Fig.37

Flag-shaped clouds - form behind the tops of mountains during strong winds. Sometimes it consists of snow. Fig.38

Rotor clouds - can form on the leeward side of the mountain, behind the ridge in strong winds and have the form of long ropes located along the mountain. They form on the ascending sides of the rotor and are destroyed on the descending ones. Indicates severe turbulence. Fig. 39

Wave or lenticular clouds - are formed by wave movement of air during strong winds. They do not move relative to the ground. Fig.40

Rice. 37 Fig. 38 Fig.39

Ribbed clouds are very similar to ripples on water. Formed when one layer of air moves over another at a speed sufficient to form waves. They move with the wind. Fig.41

Pileus - when a thundercloud develops to an inversion layer. A thundercloud can break through the inversion layer. Rice. 42

Rice. 40 Fig. 41 Fig. 42

Cloud formation.

Clouds consist of countless microscopic particles of water of various sizes: from 0.001 cm in saturated air to 0.025 with ongoing condensation. The main way clouds form in the atmosphere is by cooling moist air. This occurs when the air cools as it rises.

Fog forms in cooling air from contact with the ground.

Updrafts.

There are three main reasons why updrafts occur. These are flows due to the movement of fronts, dynamic and thermal.

front dynamic thermal

The rate of rise of the frontal flow directly depends on the speed of the front and is usually 0.2-2 m/s. In a dynamic flow, the rate of rise depends on the strength of the wind and the steepness of the slope, and can reach up to 30 m/s. Thermal flow occurs when warmer air rises and is heated by the earth's surface on sunny days. The lifting speed reaches 15 m/s, but usually it is 1-5 m/s.

Dew point and cloud height.

The saturation temperature is called the dew point. Let’s assume that the rising air cools in a certain way, for example, 1 0 C/100 m. But the dew point drops only by 0.2 0 C/100 m. Thus, the dew point and the temperature of the rising air approach 0.8 0 C/100 m. When they equalize, clouds will form. Meteorologists use dry and wet bulb thermometers to measure ground and saturation temperatures. From these measurements you can calculate the cloud base. For example: the air temperature at the surface is 31 0 C, the dew point is 15 0 C. Dividing the difference by 0.8 we get a base equal to 2000 m.

Life of the clouds.

During their development, clouds go through the stages of origin, growth and decay. One isolated cumulus cloud lives for about half an hour from the moment the first signs of condensation appear until it disintegrates into an amorphous mass. However, often the clouds do not break up as quickly. This occurs when the air humidity at the level of the clouds and the humidity of the cloud coincide. The mixing process is in progress. In fact, ongoing thermality results in a gradual or rapid spread of cloud cover over the entire sky. This is called overdevelopment or OD in the pilot's lexicon.

Continued thermality can also fuel individual clouds, increasing their lifetime by more than 0.5 hours. In fact, thunderstorms are long-lived clouds formed by thermal currents.

Precipitation.

For precipitation to occur, two conditions are necessary: ​​prolonged updrafts and high humidity. Water droplets or ice crystals begin to grow in the cloud. When they get big, they start to fall. Snowing, rain or hail.

"PRACTICAL AVIATION METEOROLOGY Tutorial for flight and traffic control personnel of Civil Aviation Compiled by V.A. Pozdnyakova, teacher of the Ural Training Center of Civil Aviation. Ekaterinburg 2010...”

-- [ Page 1 ] --

Ural Training Center of Civil Aviation

PRACTICAL AVIATION

METEOROLOGY

Training manual for flight and air traffic control personnel

Compiled by a teacher of the Ural Training Center of Civil Aviation

Pozdnyakova V.A.

Ekaterinburg 2010

pages

1 Structure of the atmosphere 4

1.1 Atmospheric research methods 5

1.2 Standard atmosphere 5-6 2 Meteorological quantities

2.1 Air temperature 6-7

2.2 Air density 7

2.3 Humidity 8

2.4 Atmospheric pressure 8-9

2.5 Wind 9

2.6 Local winds 10 3 Vertical air movements

3.1 Causes and types of vertical air movements 11 4 Clouds and precipitation

4.1 Causes of cloud formation. Cloud classification 12-13

4.2 Cloud observations 13

4.3 Precipitation 14 5 Visibility 14-15 6 Atmospheric processes that cause weather 16

6.1 Air masses 16-17

6.2 Atmospheric fronts 18

6.3 Warm front 18-19

6.4 Cold front 19-20

6.5 Occlusion fronts 20-21

6.6 Secondary fronts 22

6.7 Upper warm front 22

6.8 Stationary fronts 22 7 Pressure systems

7.1 Cyclone 23

7.2 Anticyclone 24

7.3 Movement and evolution of pressure systems 25-26

8. High-altitude frontal zones 26

–  –  –

INTRODUCTION

Meteorology is the science of the physical state of the atmosphere and the phenomena occurring in it.

Aviation meteorology is the study of meteorological elements and atmospheric processes from the point of view of their influence on aviation activities, and also develops methods and forms of meteorological support for flights.

Aircraft flights without meteorological information are impossible. This rule applies to all airplanes and helicopters without exception in all countries of the world, regardless of the length of the routes. All flights of civil aviation aircraft can be carried out only if the flight crew knows the meteorological situation in the flight area, landing point and at alternate airfields. Therefore, it is necessary that every pilot has a perfect command of the necessary meteorological knowledge, understands the physical essence of weather phenomena, their connection with the development of synoptic processes and local physical and geographical conditions, which is the key to flight safety.

The proposed textbook sets out in a concise and accessible form the concepts of basic meteorological quantities and phenomena in connection with their influence on the operation of aviation. The meteorological conditions of the flight are considered and practical recommendations are given on the most appropriate actions of the flight crew in difficult meteorological conditions.

1. The structure of the atmosphere The atmosphere is divided into several layers or spheres that differ from each other physical properties. The difference between the layers of the atmosphere is most clearly manifested in the nature of the distribution of air temperature with height. On this basis, five main spheres are distinguished: the troposphere, stratosphere, mesosphere, thermosphere and exosphere.

Troposphere - extends from the earth's surface to an altitude of 10-12 km in temperate latitudes. It is lower at the poles and higher at the equator. The troposphere contains about 79% of the total mass of the atmosphere and almost all water vapor. Here there is a decrease in temperature with height, vertical air movements take place, and westerly winds, clouds and precipitation occur.

There are three layers in the troposphere:

a) Boundary (friction layer) - from the ground to 1000-1500 m. This layer is affected by the thermal and mechanical effects of the earth’s surface. The daily cycle of meteorological elements is observed. The lower part of the boundary layer, up to 600 m thick, is called the “ground layer”. Here the influence of the earth's surface is most strongly felt, as a result of which meteorological elements such as temperature, air humidity, and wind experience sudden changes with height.

The nature of the underlying surface largely determines the weather conditions of the surface layer.

b) The middle layer is located from the upper boundary of the boundary layer and extends to a height of 6 km. In this layer there is almost no influence of the earth's surface. Here weather conditions are determined mainly by atmospheric fronts and vertical convective air currents.

c) The top layer lies above the middle layer and extends to the tropopause.

Tropopause is a transition layer between the troposphere and stratosphere with a thickness of several hundred meters to 1-2 km. The lower limit of the tropopause is taken to be the altitude where the drop in temperature with height is replaced by an even temperature change, an increase or slowdown in the drop with height.

When crossing the tropopause at the flight level, changes in temperature, moisture content and air transparency may be observed. The maximum wind speed is usually located in the tropopause zone or below its lower boundary.

The height of the tropopause depends on the temperature of the tropospheric air, i.e. on the latitude of the place, time of year, the nature of synoptic processes (in warm air it is higher, in cold air it is lower).

The stratosphere extends from the tropopause to an altitude of 50-55 km. The temperature in the stratosphere increases and at the upper boundary of the stratosphere approaches 0 degrees. It contains about 20% of the total mass of the atmosphere. Due to the insignificant content of water vapor in the stratosphere, clouds do not form, with the rare exception of the occasional nacreous clouds consisting of tiny supercooled droplets of water. Winds predominate from the west, in summer above 20 km there is a transition to east winds. The tops of cumulonimbus clouds can penetrate into the lower layers of the troposphere from the upper troposphere.

Above the stratosphere lies an air gap - the stratopause, separating the stratosphere from the mesosphere.

The mesosphere is located from a height of 50-55 km and extends to a height of 80 -90 km.

The temperature here decreases with altitude and reaches values ​​of about -90°.

The transition layer between the mesosphere and thermosphere is the mesopause.

The thermosphere occupies altitudes from 80 to 450 km. According to indirect data and the results of rocket observations, the temperature here increases sharply with altitude and at the upper boundary of the thermosphere can be 700°-800°.

The exosphere is the outer layer of the atmosphere over 450 km.

1.1 Methods for studying the atmosphere Direct and indirect methods are used to study the atmosphere. Direct methods include, for example, meteorological observations, radio sounding of the atmosphere, radar observations. Meteorological rockets and artificial Earth satellites equipped with special equipment are used.

In addition to direct methods, valuable information about the state of the high layers of the atmosphere is provided by indirect methods based on the study of geophysical phenomena occurring in high layers of the atmosphere.

Conducted laboratory experiments and mathematical modeling (a system of formulas and equations that allow obtaining numerical and graphical information about the state of the atmosphere).

1.2.Standard atmosphere The movement of an aircraft in the atmosphere is accompanied by complex interaction with it environment. From physical condition The atmosphere depends on the aerodynamic forces arising in flight, the thrust force created by the engine, fuel consumption, speed and maximum permissible flight altitude, readings of aeronautical instruments (barometric altimeter, speed indicator, Mach number indicator), etc.

The real atmosphere is very variable, so the concept of a standard atmosphere has been introduced for the design, testing and operation of aircraft. SA is the estimated vertical distribution of temperature, pressure, air density and other geophysical characteristics, which by international agreement represents the average annual and mid-latitude state of the atmosphere. Basic parameters of the standard atmosphere:

The atmosphere at all altitudes consists of dry air;

The average sea level at which the air pressure is 760 mm Hg is taken as zero altitude (“ground”). Art. or 1013.25 hPa.

Temperature +15°C

Air density is 1.225 kg/m2;

The boundary of the troposphere is considered to lie at an altitude of 11 km; the vertical temperature gradient is constant and equal to 0.65°C per 100m;

In the stratosphere, i.e. above 11 km, the temperature is constant and equal to -56.5 ° C.

2. Meteorological quantities

2.1 Air temperature Atmospheric air is a mixture of gases. The molecules in this mixture are in continuous motion. Each state of a gas corresponds to a certain speed of molecular movement. The higher the average speed of molecular movement, the higher the air temperature. Temperature characterizes the degree of air heating.

For quantitative characteristics of temperature, the following scales are adopted:

The centigrade scale is the Celsius scale. On this scale, 0°C corresponds to the melting point of ice, 100°C corresponds to the boiling point of water, at a pressure of 760 mmHg.

Fahrenheit. The temperature of the mixture of ice and ammonia (-17.8° C) is taken as the lower temperature of this scale; the temperature of the human body is taken as the upper temperature. The interval is divided into 96 parts. Т°(С)=5/9 (Т°(Ф) -32).

In theoretical meteorology, an absolute scale is used - the Kelvin scale.

The zero of this scale corresponds to the complete cessation of thermal motion of molecules, i.e. lowest possible temperature. Т°(К)= Т°(С)+273°.

Heat is transferred from the earth's surface to the atmosphere through the following main processes: thermal convection, turbulence, radiation.

1) Thermal convection is the vertical rise of air heated over individual areas of the earth's surface. The strongest development of thermal convection is observed in the daytime (afternoon) hours. Thermal convection can spread to the upper boundary of the troposphere, carrying out heat exchange throughout the entire thickness of the tropospheric air.

2) Turbulence is a countless number of small vortices (from the Latin turbo-vortex, whirlpool) that arise in a moving air flow due to its friction with the earth's surface and internal friction of particles.

Turbulence promotes air mixing and, consequently, heat exchange between the lower (hot) and upper (cold) layers of air. Turbulent heat exchange is mainly observed in the surface layer up to a height of 1-1.5 km.

3) Radiation is the return by the earth’s surface of the heat it received as a result of the influx solar radiation. Heat rays are absorbed by the atmosphere, resulting in an increase in air temperature and cooling of the earth's surface. The radiated heat heats the ground air, and the earth's surface cools due to heat loss. The radiation process takes place at night, and in winter it can be observed throughout the day.

Of the three main processes of heat transfer from the earth's surface to the atmosphere considered, the main role is played by thermal convection and turbulence.

Temperature can change both horizontally along the earth's surface and vertically as it rises upward. The magnitude of the horizontal temperature gradient is expressed in degrees over a certain distance (111 km or 1° meridian). The greater the horizontal temperature gradient, the more dangerous phenomena (conditions) are formed in the transition zone, i.e. The activity of the atmospheric front increases.

The value characterizing the change in air temperature with height is called the vertical temperature gradient; its value is variable and depends on the time of day, year, and weather patterns. According to ISA y = 0.65° /100 m.

The layers of the atmosphere in which the temperature increases with height (у0°С) are called inversion layers.

Air layers in which the temperature does not change with height are called isothermal layers (y = 0 ° C). They are retaining layers: they dampen vertical air movements, under them there is an accumulation of water vapor and solid particles that impair visibility, fogs and low clouds are formed. Inversions and isotherms can lead to significant vertical stratification of flows and the formation of significant vertical meter shifts, which causes aircraft to sway and affects flight dynamics during approach or takeoff.

Air temperature affects the flight of an airplane. The takeoff and landing performance of an aircraft largely depends on temperature. The length of the run and take-off distance, the length of the run and the landing distance decrease with decreasing temperature. Air density, which determines the flight characteristics of an aircraft, depends on temperature. As the temperature increases, the density decreases, and, consequently, the velocity pressure decreases and vice versa.

A change in speed pressure causes a change in engine thrust, lift, drag, horizontal and vertical speed. Air temperature affects flight altitude. Thus, increasing it at high altitudes by 10° from the standard leads to a lowering of the aircraft ceiling by 400-500 m.

Temperature is taken into account when calculating a safe flight altitude. Very low temperatures complicate the operation of aircraft. At air temperatures close to 0°C and below, with supercooled precipitation, ice forms, and when flying in the clouds - icing. Temperature changes of more than 2.5°C per 100 km cause atmospheric turbulence.

2.2 Air Density Air density is the ratio of the mass of air to the volume it occupies.

Air density determines the flight characteristics of an aircraft. The velocity head depends on the air density. The larger it is, the greater the velocity pressure and, therefore, the greater the aerodynamic force. The density of air, in turn, depends on temperature and pressure. From the Clapeyron-Mendeleev equation of state for an ideal gas P Density b-xa = ------, where R is the gas constant.

RT P-air pressure T-gas temperature.

As can be seen from the formula, as the temperature increases, the density decreases, and therefore the velocity pressure decreases. When the temperature decreases, the opposite picture is observed.

A change in speed pressure causes a change in engine thrust, lift, drag and, consequently, the horizontal and vertical speeds of the aircraft.

The length of the run and landing distance is inversely proportional to air density and, therefore, temperature. A decrease in temperature by 15°C reduces the run length and take-off distance by 5%.

An increase in air temperature at high altitudes by 10° leads to a decrease in the practical ceiling of the aircraft by 400-500 m.

2.3 Air humidity Air humidity is determined by the water vapor content in the atmosphere and is expressed using the following basic characteristics.

Absolute humidity is the amount of water vapor in grams contained in 1 m3 of air. The higher the air temperature, the greater the absolute humidity. It is used to judge the occurrence of vertical clouds and thunderstorm activity.

Relative humidity is characterized by the degree of saturation of air with water vapor. Relative humidity is the percentage of the actual amount of water vapor contained in the air to the amount required for complete saturation at a given temperature. At a relative humidity of 20-40% the air is considered dry, at 80-100% - humid, at 50-70% - air of moderate humidity. As relative humidity increases, cloudiness decreases and visibility deteriorates.

Dew point temperature is the temperature at which water vapor contained in the air reaches a state of saturation at a given moisture content and constant pressure. The difference between the actual temperature and the dew point temperature is called the dew point deficit. The deficit shows how many degrees the air must be cooled in order for the steam contained in it to reach a state of saturation. At dew point deficits of 3-4° or less, the air mass near the ground is considered humid, and at 0-1°, fogs often occur.

The main process leading to the saturation of air with water vapor is a decrease in temperature. Water vapor plays an important role in atmospheric processes. It strongly absorbs thermal radiation emitted by the earth's surface and atmosphere, and thereby reduces heat loss from our planet. The main influence of humidity on aviation operations is through cloudiness, precipitation, fog, thunderstorms, and icing.

2.4 Atmospheric pressure Atmospheric air pressure is the force acting on a unit of horizontal surface of 1 cm2 and equal to the weight of the air column extending through the entire atmosphere. Changes in pressure in space are closely related to the development of basic atmospheric processes. In particular, horizontal pressure inhomogeneity is the cause of air flows. The value of atmospheric pressure is measured in mmHg.

millibars and hectopascals. There is a dependency between them:

–  –  –

1 mmHg = 1.33 mb = 1.33 hPa 760 mm Hg. = 1013.25 hPa.

The change in pressure in the horizontal plane per unit distance (1° of the meridian arc (111 km) or 100 km is taken as a unit of distance) is called the horizontal pressure gradient. It's always facing away low pressure. The wind speed depends on the magnitude of the horizontal pressure gradient, and the wind direction depends on its direction. In the northern hemisphere, the wind blows at an angle to the horizontal pressure gradient, so that if you stand with your back to the wind, low pressure will be to the left and somewhat ahead, and high pressure will be to the right and somewhat behind the observer.

For a visual representation of the distribution of atmospheric pressure, lines are drawn on weather maps - isobars connecting points with the same pressure. Isobars highlight pressure systems on maps: cyclones, anticyclones, troughs, ridges and saddles. Changes in pressure at any point in space over a period of time of 3 hours are called the baric trend; its value is plotted on ground-level synoptic weather maps, on which lines of equal baric trends - isallobars - are drawn.

Atmospheric pressure decreases with altitude. When conducting and managing flights, it is necessary to know the change in altitude depending on the vertical change in pressure.

This value is characterized by the pressure level - which determines the height to which one must rise or fall in order for the pressure to change by 1 mm Hg. or per 1 hPa. It is equal to 11 m per 1 mmHg, or 8 m per 1 hPa. At an altitude of 10 km, the step is 31 m with a pressure change of 1 mm Hg.

To ensure flight safety, crews are provided with air pressure in the weather, normalized to the threshold level of the working start runway in mmHg, mb, or pressure normalized to sea level for a standard atmosphere, depending on the type of aircraft.

The barometric altimeter on an airplane is based on the principle of measuring altitude by pressure. Since in flight the flight altitude is maintained according to the barometric altimeter, i.e. Since the flight occurs at constant pressure, the flight is actually carried out on an isobaric surface. The uneven height of the isobaric surfaces leads to the fact that the true flight altitude can differ significantly from the instrument altitude.

So, above a cyclone it will be lower than the instrument one and vice versa. This should be taken into account when determining a safe flight level and when flying at altitudes close to the ceiling of the aircraft.

2.5 Wind In the atmosphere, horizontal movements of air, called wind, are always observed.

The immediate cause of wind is the uneven distribution of air pressure along the surface of the earth. The main characteristics of the wind are: direction / part of the horizon from where the wind blows / and speed, measured in m/sec, knots (1 knot ~ 0.5 m/s) and km/hour (I m/sec = 3.6 km/hour).

Wind is characterized by gusty speed and variability of direction. To characterize the wind, the average speed and average direction are determined.

Using instruments, the wind is determined from the true meridian. At those airports where the magnetic declination is 5° or more, corrections for magnetic declination are introduced into the heading indication for transmission to ATS units, crews, and in AT1S and VHF weather reports. In reports disseminated beyond the aerodrome, the wind direction is indicated from the true meridian.

Averaging occurs 10 minutes before the release of the report outside the aerodrome and 2 minutes at the aerodrome (on ATIS and at the request of the air traffic controller). Gusts are indicated in relation to the average speed in case of a difference of 3 m/s if the wind is cross (at each airport their gradations), and in other cases after 5m/s.

A squall is a sharp, sudden increase in wind that occurs over 1 minute or more, with the average speed differing by 8 m/s or more from the previous average speed and with a change in direction.

The duration of the squall is usually several minutes, the speed often exceeds 20-30 m/s.

The force that causes a mass of air to move horizontally is called the pressure gradient force. The greater the pressure drop, the stronger wind. The movement of air is influenced by the Coriolis force, the force of friction. The Coriolis force deflects all air currents to the right in the Northern Hemisphere and does not affect wind speed. The friction force acts opposite to the movement and decreases with height (mainly in the ground layer) and has no effect above 1000-1500m. The friction force reduces the angle of deviation of the air flow from the direction of the horizontal pressure gradient, i.e. also affects the direction of the wind.

Gradient wind is the movement of air in the absence of friction. All wind above 1000m is practically gradient.

The gradient wind is directed along the isobars so that low pressure will always be to the left of the flow. In practice, the wind at altitudes is predicted from pressure topography maps.

The wind is exerting big influence for flights of all types of aircraft. The safety of aircraft takeoff and landing depends on the direction and speed of the wind relative to the runway. Wind affects the length of the aircraft's takeoff and run. Side winds are also dangerous, causing the plane to drift away. The wind calls dangerous phenomena, complicating flights, such as hurricanes, squalls, dust storms, blizzards. The wind structure is turbulent, which causes the aircraft to bounce and throw. When choosing an aerodrome runway, the prevailing wind direction is taken into account.

2.6 Local winds Local winds are an exception to the pressure law of wind: they blow along a horizontal pressure gradient, which appears in a given area due to unequal heating of different parts of the underlying surface or due to the relief.

These include:

Breezes that are observed on the coast of seas and large bodies of water, blowing onto land from the water surface during the day and vice versa at night, they are respectively called sea and coastal breezes, speed 2-5 m/sec, vertically spreading up to 500-1000 m. The reason for their occurrence uneven heating of water and land. Breezes influence weather conditions in the coastal strip, causing a decrease in temperature, an increase in absolute humidity, and wind shifts. Breezes are pronounced on the Black Sea coast of the Caucasus.

Mountain-valley winds arise as a result of uneven heating and cooling of air directly at the slopes. During the day, the air rises up the slope of the valley and is called the valley wind. At night it descends from the slopes and is called mountain. A vertical thickness of 1500 m often causes bumpiness.

Foehn is a warm, dry wind blowing from the mountains to the valleys, sometimes reaching gale force. The foehn effect is expressed in the area high mountains 2-3km. It occurs when a pressure difference is created on opposite slopes. On one side of the ridge there is an area of ​​low pressure, on the other there is an area of ​​high pressure, which contributes to the movement of air over the ridge. On the windward side, the rising air is cooled to the level of condensation (conventionally the lower boundary of the clouds) according to the dry adiabatic law (1°/100 m.), then according to the moist adiabatic law (0.5°-0.6°/100 m.), which leads to the formation of clouds and precipitation. When the stream crosses the ridge, it begins to quickly fall down the slope and heat up (1°/100m). As a result, on the leeward side of the ridge the clouds are washed away and the air reaches the foot of the mountains very dry and warm. During a foehn, difficult weather conditions are observed on the windward side of the ridge (fog, precipitation) and partly cloudy weather on the leeward side of the ridge, but here there is intense turbulence of the aircraft.

Bora is a strong gusty wind blowing from low coastal mountains (no more than 1000

m) towards the warm sea. It is observed in the autumn-winter period, accompanied by a sharp drop in temperature, expressed in the region of Novorossiysk, in the north-eastern direction. Bora occurs in the presence of an anticyclone formed and located over the eastern and south-eastern regions of the European territory of Russia, and at this time there is an area of ​​low pressure over the Black Sea, while large pressure gradients are created and cold air rushes through the Markhotsky pass from a height of 435 m to Novorossiysk bay at a speed of 40-60 m/sec. Bora causes a storm at sea, ice, extends 10-15 km deep into the sea, lasting up to 3 days, and sometimes more.

Very strong boron is formed on Novaya Zemlya. On Baikal, a bora-type wind is formed at the mouth of the Sarma River and is locally called “Sarma”.

Afghan - a very strong, dusty westerly or southwest wind in the eastern Karakum desert, up the valleys of the Amu Darya, Syrdarya and Vakhsh rivers. Accompanied by a dust storm and thunderstorm. Afghan emerges in connection with frontal invasions of cold into the Turan Lowland.

Local winds specific to certain areas have a major impact on aviation operations. Increased wind caused by the terrain features of a given area makes it difficult to pilot aircraft at low altitudes, and sometimes is dangerous for the flight.

When air flows over mountain ranges, leeward waves are formed in the atmosphere. They occur under the following conditions:

The presence of wind blowing perpendicular to the ridge, the speed of which is 50 km/h or more;

Wind speed increases with height;

The presence of inversion or isothermal layers from the top of the ridge at 1-3 km. Leeward waves cause intense vibration of aircraft. They are characterized by lenticular altocumulus clouds.

3.Vertical air movements

3.1 Causes and types of vertical air movements Vertical movements constantly occur in the atmosphere. They are playing vital role in such atmospheric processes as vertical transfer of heat and water vapor, formation of clouds and precipitation, cloud dispersion, development of thunderstorms, occurrence of turbulent zones, etc.

Depending on the causes of occurrence, the following types of vertical movements are distinguished:

Thermal convection - occurs due to uneven heating of air from the underlying surface. More heated volumes of air, becoming lighter than the environment, rise upward, giving way to denser cold air falling down. The speed of upward movements can reach several meters per second, and in some cases 20-30 m/s (in powerful cumulus, cumulonimbus clouds).

Downdrafts have a smaller magnitude (~ 15 m/s).

Dynamic convection or dynamic turbulence is disordered vortex movements that occur during horizontal movement and friction of air against the earth's surface. The vertical components of such movements can be several tens of cm/s, less often up to several m/s. This convection is well expressed in the layer from the ground to a height of 1-1.5 km (boundary layer).

Thermal and dynamic convection are often observed simultaneously, determining the unstable state of the atmosphere.

Ordered, forced vertical movements are the slow upward or downward movement of the entire air mass. This may be a forced rise of air in the area atmospheric fronts, in mountainous areas on the windward side or a slow, quiet “settling” of the air mass as a result of the general circulation of the atmosphere.

The convergence of air flows in the upper layers of the troposphere (convergence) of air flows in the upper layers of the atmosphere causes an increase in pressure near the ground and downward vertical movements in this layer.

The divergence of air flows at altitudes (divergence), on the contrary, leads to a drop in pressure near the ground and the rise of air upward.

Wave movements arise due to the difference in air density and the speed of its movement at the upper and lower boundaries of the inversion and isotherm layers. In the crests of the waves, upward movements are formed, in the valleys - downward movements. Wave movements in the atmosphere can be observed in the mountains on the leeward side, where leeward (standing) waves are formed.

When flying in an air mass where highly developed vertical currents are observed, the aircraft experiences bumps and surges, which complicate piloting. Large-scale vertical air flows can cause large vertical movements of the aircraft independent of the pilot. This can be particularly dangerous when flying at altitudes close to the aircraft's service ceiling, where updrafts can lift the aircraft to an altitude well above its ceiling, or when flying in mountainous areas on the leeward side of a ridge, where downdrafts can cause the aircraft to collide with the ground. .

Vertical air movements lead to the formation of cumulonimbus clouds that are dangerous for flight.

4.Clouds and precipitation

4.1 Causes of cloud formation. Classification.

Clouds are a visible accumulation of water droplets and ice crystals suspended in the air at some height above the earth's surface. Clouds are formed as a result of condensation (transition of water vapor into a liquid state) and sublimation (transition of water vapor directly into a solid state) of water vapor.

The main reason for the formation of clouds is an adiabatic (without exchange of heat with the environment) decrease in temperature in rising moist air, leading to condensation of water vapor; turbulent exchange and radiation, as well as the presence of condensation nuclei.

Cloud microstructure - the phase state of cloud elements, their sizes, the number of cloud particles per unit volume. Clouds are divided into ice, water and mixed (from crystals and droplets).

According to the international classification, clouds are divided into 10 main forms by appearance, and into four classes by height.

1. Upper tier clouds - located at an altitude of 6000 m and above, they are thin white clouds, consist of ice crystals, have little water content, so they do not produce precipitation. Thickness is low: 200 m - 600 m. These include:

Cirrus clouds/Ci-cirrus/, looking like white threads, hooks. They are harbingers of worsening weather, the approach of a warm front;

Cirrocumulus clouds /Cc- cirrocumulus/ - small wings, small white flakes, ripples. The flight is accompanied by a slight bump;

Cirrostratus/Cs-cirrostratus/ have the appearance of a bluish uniform veil that covers the entire sky, a blurry disk of the sun is visible, and at night a halo circle appears around the moon. Flight in them may be accompanied by slight icing and electrification of the aircraft.

2. Middle-level clouds are located at an altitude of up to

2 km 6 km, consist of supercooled drops of water mixed with snowflakes and ice crystals, flights in them are accompanied by poor visibility. These include:

Altocumulus / Ac-altocumulus / having the appearance of flakes, plates, waves, ridges, separated by gaps. Vertical length 200-700m. There is no precipitation, the flight is accompanied by bumpiness and icing;

High-layered / As-altostratus / are a continuous gray veil, thin high-layered have a thickness of 300-600 m, dense - 1-2 km. In winter, they receive heavy precipitation.

The flight is accompanied by icing.

3. Low-level clouds range from 50 to 2000 m, have a dense structure, poor visibility, and icing is often observed. These include:

Nimbostratus (Ns-nimbostratus), having a dark gray color, high water content, give abundant continuous precipitation. Below them, low fractonic rain/Frnb-fractonimbus/ clouds are formed in the precipitation. The height of the lower boundary of nimbostratus clouds depends on the proximity of the front line and ranges from 200 to 1000 m, the vertical extent is 2-3 km, often merging with altostratus and cirrostratus clouds;

Stratocumulus/Sc-stratocumulus/ consist of large ridges, waves, plates separated by gaps. The lower limit is 200-600 m, and the thickness of the clouds is 200-800 m, sometimes 1-2 km. These are intramass clouds; in the upper part of stratocumulus clouds there is the greatest water content, and there is also an icing zone. As a rule, no precipitation falls from these clouds;

Stratus clouds (St-stratus) are a continuous, homogeneous cover, hanging low above the ground with jagged, blurry edges. The height is 100-150 m and below 100 m, and the upper limit is 300-800 m. They make take-off and landing very difficult and cause drizzling precipitation. They can sink to the ground and turn into fog;

Fractured-stratus/St Fr-stratus fractus/ clouds have a lower limit of 100 m and below 100 m, they are formed as a result of the dispersion of radiation fog, precipitation does not fall from them.

4. Clouds of vertical development. Their lower boundary lies in the lower tier, the upper reaches the tropopause. These include:

Cumulus clouds (Cu cumulus) are dense cloud masses developed vertically with white dome-shaped tops and a flat base. Their lower limit is about 400-600 m and higher, the upper limit is 2-3 km, they do not produce precipitation. Flight in them is accompanied by bumpiness, which does not significantly affect the flight mode;,..

Powerful cumulus (Cu cong-cumulus congestus) clouds are white dome-shaped peaks with a vertical development of up to 4-6 km; they do not produce precipitation. Flight in them is accompanied by moderate to strong turbulence, so entering these clouds is prohibited;

Cumulonimbus (thunderstorm)/Cb-cumulonimbus/ are the most dangerous clouds; they are powerful masses of swirling clouds with a vertical development of up to 9-12 km and higher. They are associated with thunderstorms, showers, hail, intense icing, intense turbulence, squalls, tornadoes, and wind shears. At the top, cumulonimbus looks like an anvil, in the direction of which the cloud moves.

Depending on the causes of occurrence, the following types of cloud forms are distinguished:

1. Cumulus. The reason for their occurrence is thermal, dynamic convection and forced vertical movements.

These include:

a) cirrocumulus /Cc/

b) altocumulus /Ac/

c) stratocumulus/Sc/

d) powerful cumulus / Cu cong /

e) cumulonimbus/Cb/

2. Stratus arises as a result of upward sliding of warm moist air along the inclined surface of cold air, along flat frontal sections. Clouds of this type include:

a) cirrostratus/Cs/

b) highly layered/As/

c) nimbostratus/ Ns/

3. Wavy, occur during wave oscillations on inversion, isothermal layers and in layers with a small vertical temperature gradient.

These include:

a) altocumulus undulate

b) stratocumulus wavy.

4.2 Observations of clouds Observations of clouds determine: total clouds (indicated in octants.) the number of clouds in the lower tier, the shape of the clouds.

The height of the lower clouds is determined instrumentally using the IVO, DVO light locator with an accuracy of ±10% in the altitude range from 10 m to 2000 m. In the absence of instrumental means, the height is estimated from the data of the aircraft crews or visually.

During fog, precipitation or a dust storm, when the lower boundary of the clouds cannot be determined, the results of instrumental measurements are indicated in reports as vertical visibility.

At airfields equipped with landing approach systems, the height of the cloud base at values ​​of 200 m and below is measured using sensors installed in the area of ​​the BPRM. In other cases, measurements are made at working starts. When estimating the expected height of low clouds, the terrain is taken into account.

Over elevated places, clouds are located 50-60% lower than the difference in elevation of the points themselves. Above forest areas cloudiness is always lower. Over industrial centers, where there are many condensation nuclei, the frequency of cloudiness increases. The lower edge of low clouds of stratus, stratus, fractus and nimbus is uneven, variable and experiences significant fluctuations within the range of 50-150 m.

Clouds are one of the most important meteorological elements affecting flights.

4.3 Precipitation Water droplets or ice crystals falling from clouds onto the Earth's surface are called precipitation. Precipitation usually falls from those clouds that are mixed in structure. For precipitation to occur, droplets or crystals must become larger to 2-3 mm. Enlargement of droplets occurs due to their merging upon collision.

The second process of enlargement is associated with the transfer of water vapor from water droplets to the crystal, and it grows, which is associated with different saturation elasticity above water and above ice. Precipitation occurs from clouds that reach those levels where active crystal formation occurs, i.e. where temperatures range from -10°C to 16°C and below. Based on the nature of precipitation, precipitation is divided into 3 types:

Cover precipitation - falls over a long period of time and large territory from nimbostratus and altostratus clouds;

Rainfall from cumulonimbus clouds, in a limited area, in a short period of time and in large quantities; The drops are larger, the snowflakes are flakes.

Drizzle - from stratus clouds, these are small droplets, the fall of which is not noticeable to the eye.

By type they distinguish: rain, snow, freezing rain passing through the ground layer of air with a negative temperature, drizzle, graupel, hail, snow grains, etc.

Precipitation includes: dew, frost, frost and snowstorms.

In aviation, precipitation that leads to the formation of ice is called supercooled. These are supercooled drizzle, supercooled rain and supercooled fog (observed or predicted in temperature gradations from -0° to -20°C). Precipitation complicates the flight of an aircraft - it impairs horizontal visibility. Precipitation is considered heavy when visibility is less than 1000 m, regardless of the nature of the fall (cover, shower, drizzle). In addition, the water film on the cabin glass causes optical distortion of visible objects, which is dangerous for takeoff and landing. Precipitation affects the condition of airfields, especially unpaved ones, and supercooled rain causes ice and icing. Getting into the hail zone causes serious technical damage. When landing on a wet runway, the aircraft's runway length changes, which can lead to overrunning the runway. The jet of water thrown from the landing gear can be sucked into the engine, causing a loss of thrust, which is dangerous during takeoff.

5. Visibility

There are several definitions of visibility:

Meteorological visibility range /MVD/ is the greatest distance from which, during daylight hours, a black object of sufficiently large size can be distinguished against the background of the sky near the horizon. At night, the distance to the most distant visible point source of light of a certain strength.

Meteorological visibility range is one of the meteorological elements important for aviation.

To monitor visibility at each aerodrome, a landmark diagram is drawn up and visibility is determined using instrumental systems. Upon reaching SMU (200/2000) - visibility measurement should be carried out using instrumental systems with recording of readings.

The averaging period is -10 minutes. for reports outside the airfield; 1 min. - for local regular and special reports.

Runway visual range /RVR/ - the visual range within which the pilot of an aircraft located on center line runway, can see the runway pavement markings or lights that indicate the contours of the runway and its center line.

Visibility observations are made along the runway using instruments or on boards on which single light sources (60 W bulbs) are installed to assess visibility in the dark.

Since visibility can be very variable, visibility measuring instruments are installed at the traffic control points of both courses and in the middle of the runway. The weather report includes:

a) with a runway length and less - the lesser of two values ​​of 2000 m of visibility measured at both ends of the runway;

b) with a runway length of more than 2000 m - the lesser of two visibility values ​​measured at the working start and the middle of the runway.

At airfields where OVI lighting systems are used with visibility of 1500 m or less at dusk and at night, 1000 m or less during the day, recalculation is carried out using tables into OVI visibility, which is also included in aviation weather. Recalculation of visibility into OMI visibility only at night.

In difficult weather conditions, especially when the plane is landing, it is important to know the oblique visibility. Slope visibility (landing) is the maximum slope distance along the descent glide path at which the pilot of a landing aircraft, when transitioning from instrument piloting to visual piloting, can detect the beginning of the runway. It is not measured, but assessed. The following dependence of oblique visibility on the magnitude of horizontal visibility at different cloud heights has been experimentally established:

When the height of the cloud base is less than 100 m and visibility is deteriorated due to haze and precipitation near the ground, oblique visibility is 25-45% of horizontal visibility;

When the height of the lower edge of the clouds is 100-150 m, it is equal to 40-50% of the horizontal; - at a height of the cloud boundary of 150-200 m, the inclined one is 60-70% of the horizontal;

–  –  –

When the height of the NGO is more than 200 m, the oblique visibility is close to or equal to the horizontal visibility at the ground.

Fig.2 Effect of atmospheric haze on oblique visibility.

inversion

6. Basic atmospheric processes that cause weather Atmospheric processes observed over large geographical areas and studied using synoptic maps are called synoptic processes.

These processes are the result of the emergence, development and interaction of air masses, the divisions between them - atmospheric fronts and cyclones and anticyclones associated with these meteorological objects.

During pre-flight preparation, the aircraft crew must study the meteorological situation and flight conditions along the route, at departure and landing airports, at alternate airfields, paying attention to the main atmospheric processes that determine the weather:

On the state of air masses;

The location of pressure formations;

The position of atmospheric fronts relative to the flight route.

6.1 Air masses Large masses of air in the troposphere that have uniform weather conditions and physical properties are called air masses (AM).

There are 2 classifications of air masses: geographical and thermodynamic.

Geographical - depending on the areas of their formation, they are divided into:

a) arctic air (AV)

b) temperate/polar/air (HC)

d) tropical air (TV)

e) equatorial air (EA) Depending on the underlying surface over which this or that air mass was located for a long time, they are divided into marine and continental.

Depending on the thermal state (relative to the underlying surface), air masses can be warm or cold.

Depending on the conditions of vertical equilibrium, stable, unstable and indifferent stratification (state) of air masses are distinguished.

Stable VM is warmer than the underlying surface. There are no conditions for the development of vertical air movements, since cooling from below reduces the vertical temperature gradient due to a decrease in the temperature contrast between the lower and top layers. Here, layers of inversion and isothermia are formed. The most favorable time for acquiring stability of VMs over the continent is during the day during the night, during the year during the year - winter.

The nature of the weather in UVM in winter: low sub-inversion stratus and stratocumulus clouds, drizzle, haze, fog, ice, icing in the clouds (Fig. 3).

Difficult conditions only for takeoff, landing and visual flights, from the ground to 1-2 km, partly cloudy above. In summer, partly cloudy weather or cumulus clouds with weak turbulence up to 500 m prevail in the UVM; visibility is somewhat impaired due to dust.

The UVM circulates in the warm sector of the cyclone and on the western periphery of anticyclones.

Rice. 3. Weather in UVM in winter.

An unstable air mass (IAM) is a cold air mass in which favorable conditions are observed for the development of upward air movements, mainly thermal convection. When moving above the warm underlying surface, the lower layers of the cold water warm up, which leads to an increase in vertical temperature gradients to 0.8 - 1.5/100 m, as a consequence of this, to the intensive development of convective movements in the atmosphere. NVM is most active in the warm season. With sufficient moisture content in the air, cumulonimbus clouds up to 8-12 km, showers, hail, intramass thunderstorms, and squally winds develop. The daily cycle of all elements is well expressed. With sufficient humidity and subsequent clearing at night, radiation fogs can occur in the morning.

Flight in this mass is accompanied by bumpiness (Fig. 4).

During the cold season, there are no difficulties in flying in NVM. As a rule, it is clear, drifting snow, blowing snow, with northern and northeastern winds, and with a northwestern invasion of cold weather, clouds with a lower boundary of at least 200-300 m of the stratocumulus or cumulonimbus type with snow charges are observed.

Secondary cold fronts may occur in the NWM. The NVM circulates in the rear part of the cyclone and on the eastern periphery of anticyclones.

6.2 Atmospheric fronts The transition zone/50-70 km/ between two air masses, characterized by a sharp change in the values ​​of meteorological elements in the horizontal direction, is called an atmospheric front. Each front is a layer of inversion /or isotherm/, but these inversions are always inclined at a slight angle to the surface of the earth towards the cold air.

The wind ahead of the front at the surface of the earth turns towards the front and intensifies; at the moment the front passes, the wind turns to the right (clockwise).

Fronts are zones of active interaction between warm and cold VMs. Along the surface of the front, an orderly rise of air occurs, accompanied by condensation of the water vapor contained in it. This leads to the formation of powerful cloud systems and precipitation at the front, causing the most difficult weather conditions for aviation.

Frontal inversions are dangerous due to bumpiness, because In this transition zone, two air masses move with different air densities, with different wind speeds and directions, which leads to the formation of vortices.

To assess the actual and expected weather conditions along the route or in the flight area, analysis of the position of atmospheric fronts relative to the flight route and their movement is of great importance.

Before departure, it is necessary to assess the activity of the front according to the following signs:

The fronts are located along the axis of the trough; the more pronounced the trough, the more active the front;

When passing through a front, the wind undergoes sharp changes in direction, convergence of current lines is observed, as well as changes in their speed;

The temperature on both sides of the front undergoes sharp changes, temperature contrasts amount to 6-10°C or more;

The pressure trend is not the same on both sides of the front; before the front it falls, behind the front it increases, sometimes the pressure change in 3 hours is 3-4 hPa or more;

Along the front line there are clouds and precipitation zones characteristic of each type of front. The wetter the VM in the frontal zone, the more active the weather. On high-altitude maps, the front is expressed in thickening of isohypses and isotherms, in sharp contrasts in temperature and wind.

The front moves in the direction and speed of that observed in the cold air gradient wind or its component directed perpendicular to the front. If the wind is directed along the front line, then it remains inactive.

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Meteorology is a science that studies the physical processes and phenomena occurring in the earth's atmosphere, in their continuous connection and interaction with the underlying surface of the sea and land.

Aviation meteorology is an applied branch of meteorology that studies the influence of meteorological elements and weather phenomena on aviation activities.

Atmosphere. The air envelope of the earth is called the atmosphere.

Based on the nature of the vertical temperature distribution, the atmosphere is usually divided into four main spheres: the troposphere, stratosphere, mesosphere, thermosphere and three transition layers between them: tropopause, stratopause and mesopause (6).

Troposphere - the lower layer of the atmosphere, height 7-10 km at the poles and up to 16-18 km in the equatorial regions. All weather phenomena develop mainly in the troposphere. In the troposphere, clouds form, fogs, thunderstorms, snowstorms occur, aircraft icing and other phenomena occur. The temperature in this layer of the atmosphere drops with altitude by an average of 6.5°C every kilometer (0.65°C per 100%).

Tropopause is a transition layer separating the troposphere from the stratosphere. The thickness of this layer ranges from several hundred meters to several kilometers.

The stratosphere is the layer of the atmosphere lying above the troposphere, up to an altitude of approximately 35 km. The vertical movement of air in the stratosphere (compared to the troposphere) is very weak or almost absent. The stratosphere is characterized by a slight decrease in temperature in the 11-25 km layer and an increase in the 25-35 km layer.

Stratopause is a transition layer between the stratosphere and mesosphere.

The mesosphere is a layer of the atmosphere extending from approximately 35 to 80 km. Characteristic of the mesosphere layer is a sharp increase in temperature from the beginning to a level of 50-55 km and a decrease to a level of 80 km.

Mesopause is a transition layer between the mesosphere and thermosphere.

Thermosphere is a layer of the atmosphere above 80 km. This layer is characterized by a continuous sharp increase in temperature with height. At an altitude of 120 km the temperature reaches +60° C, and at an altitude of 150 km -700° C.

A diagram of the structure of the atmosphere up to an altitude of 100 km is presented.

Standard atmosphere - conditional distribution by height of average values physical parameters atmosphere (pressure, temperature, humidity, etc.). For the international standard atmosphere the following conditions are accepted:

• pressure at sea level equal to 760 mm Hg. Art. (1013.2 MB);
• relative humidity 0%; temperature at sea level is -f 15° C and drops with altitude in the troposphere (up to 11,000 m) by 0.65° C for every 100 m.
• above 11,000 m the temperature is assumed to be constant and equal to -56.5 ° C.

See also:

METEOROLOGICAL ELEMENTS

The state of the atmosphere and the processes occurring in it are characterized by a number of meteorological elements: pressure, temperature, visibility, humidity, clouds, precipitation and wind.

Atmospheric pressure is measured in millimeters mercury or in millibars (1 mm Hg - 1.3332 mb). Normal pressure is taken to be Atmosphere pressure, equal to 760 mm. rt. Art., which corresponds to 1013.25 MB. Normal pressure is close to the average pressure at sea level. Pressure changes continuously both at the surface of the earth and at heights. The change in pressure with altitude can be characterized by the value of the barometric step (the height to which one must rise or fall in order for the pressure to change by 1 mm Hg, or 1 mb).

The value of the barometric stage is determined by the formula

Air temperature characterizes the thermal state of the atmosphere. Temperature is measured in degrees. The temperature change depends on the amount of heat coming from the Sun at a given geographic latitude, the nature of the underlying surface and atmospheric circulation.

In the USSR and most other countries of the world, the centigrade scale is adopted. The main (reference) points in this scale are: 0 ° C - the melting point of ice and 100 ° C - the boiling point of water at normal pressure (760 mm Hg). The interval between these points is divided into 100 equal parts. This interval is called “one degree Celsius” - 1° C.

Visibility. The range of horizontal visibility near the ground, determined by meteorologists, is understood as the distance at which an object (landmark) can still be detected by shape, color, and brightness. Visibility range is measured in meters or kilometers.

Air humidity is the content of water vapor in the air, expressed in absolute or relative units.

Absolute humidity is the amount of water vapor in grams per 1 liter3 of air.

Specific humidity is the amount of water vapor in grams per 1 kg of humid air.

Relative humidity is the ratio of the amount of water vapor contained in the air to the amount required to saturate the air at a given temperature, expressed as a percentage. From the relative humidity value you can determine how close a given humidity state is to saturation.

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

The difference between air temperature and dew point is called dew point deficit. The dew point is equal to the air temperature if its relative humidity is 100%. Under these conditions, water vapor condenses and clouds and fogs form.

Clouds are a collection of water droplets or ice crystals suspended in the air, resulting from the condensation of water vapor. When observing clouds, note their number, shape and height of the lower boundary.

The amount of clouds is assessed on a 10-point scale: 0 points means no clouds, 3 points - three quarters of the sky is covered with clouds, 5 points - half the sky is covered with clouds, 10 points - the whole sky is covered with clouds (totally cloudy). Cloud heights are measured using radars, searchlights, pilot balloons and airplanes.

All clouds, depending on the location of the height of the lower boundary, are divided into three tiers:

The upper tier is above 6000 m, it includes: cirrus, cirrocumulus, cirrostratus.

The middle tier is from 2000 to 6000 m, it includes: altocumulus, altostratus.

The lower tier is below 2000 m, it includes: stratocumulus, stratus, nimbostratus. The lower tier also includes clouds that extend over a considerable distance vertically, but whose lower boundary lies in the lower tier. These clouds include cumulonimbus and cumulonimbus. These clouds are classified as a special group of vertical development clouds. Cloudiness has the greatest impact on aviation activities, since clouds are associated with precipitation, thunderstorms, icing and severe buffeting.

Precipitation is water droplets or ice crystals that fall from clouds to the surface of the earth. According to the nature of precipitation, precipitation is divided into blanket, falling from nimbostratus and altostratus clouds in the form of raindrops average size or in the form of snowflakes; torrential, falling from cumulonimbus clouds in the form of large drops of rain, snow flakes or hail; drizzle, falling from stratus and stratocumulus clouds in the form of very small drops of rain.

Flight in a precipitation zone is difficult due to a sharp deterioration in visibility, a decrease in cloud height, bumpiness, icing in freezing rain and drizzle, and possible damage to the surface of the aircraft (helicopter) due to hail.

Wind is the movement of air relative to the earth's surface. Wind is characterized by two quantities: speed and direction. The unit of measurement for wind speed is meter per second (1 m/sec) or kilometer per hour (1 km/h). 1 m/sec = = 3.6 km/h.

The wind direction is measured in degrees, and it should be taken into account that the counting is from the north pole clockwise: the north direction corresponds to 0° (or 360°), the east - 90°, the south - 180°, the west - 270°.

Directional meteorological wind(from where it blows) differs from the aeronautical direction (where it blows) by 180°. In the troposphere, wind speed increases with height and reaches a maximum below the tropopause.

Relatively narrow zones of strong winds (speeds of 100 km/h and above) in the upper troposphere and lower stratosphere at altitudes close to the tropopause are called jet streams. The part of the jet stream where the wind speed reaches its maximum value is called the axis of the jet stream.

In size, jet streams extend thousands of kilometers in length, hundreds of kilometers in width and several kilometers in height.

Very weather dependent: snow, rain, fog, low clouds, strong gusty winds and even complete calm - unfavourable conditions for the jump. Therefore, athletes often have to sit on the ground for hours and weeks, waiting for a “window of good weather.”

Signs of persistent good weather

1. High blood pressure that rises slowly and continuously over several days.
2. Correct daily wind pattern: quiet at night, significant wind strength during the day; on the shores of seas and large lakes, as well as in the mountains, the correct change of winds is:
   • during the day - from water to land and from valleys to peaks,
   • at night - from land to water and from peaks to valleys.
3. in winter clear sky, and only in the evening, when it is calm, thin stratus clouds can float. In summer, on the contrary: cumulus clouds develop and disappear in the evening.
4. Correct daily temperature variation (increase during the day, decrease at night). IN winter time Temperatures are low and high in summer.
5. There is no precipitation; heavy dew or frost at night.
6. Ground fogs that disappear after sunrise.

Signs of persistent bad weather

1. Low pressure, changing little or decreasing even more.
2. Lack of normal diurnal cycle wind; wind speed is significant.
3. The sky is completely covered with nimbostratus or stratus clouds.
4. Prolonged rain or snowfall.
5. Minor temperature changes during the day; relatively warm in winter, cool in summer.

Signs of worsening weather

1. Pressure drop; The faster the pressure drops, the sooner the weather will change.
2. The wind intensifies, its daily fluctuations almost disappear, and the wind direction changes.
3. Cloudiness increases, and the following order of appearance of clouds is often observed: cirrus appears, then cirrostratus (their movement is so fast that it is noticeable to the eye), cirrostratus is replaced by altostratus, and the latter by nimbostratus.
4. Cumulus clouds do not dissipate or disappear in the evening, and their number even increases. If they take the form of towers, then a thunderstorm should be expected.
5. The temperature rises in winter, but in summer there is a noticeable decrease in its diurnal variation.
6. Colored circles and crowns appear around the Moon and Sun.

Signs of improving weather

1. The pressure rises.
2. Cloud cover becomes variable and breaks appear, although at times the entire sky may still be covered with low rain clouds.
3. Rain or snow falls from time to time and is quite heavy, but it does not fall continuously.
4. The temperature drops in winter and rises in summer (after a preliminary decrease).