"PRACTICAL AERONAUTICAL METEOROLOGY Tutorial for the flight and dispatching staff of civil aviation Compiled by the teacher of the Ural training center of civil aviation Pozdnyakova V.A. Yekaterinburg 2010 ... "

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Ural UTC GA

PRACTICAL AVIATION

METEOROLOGY

Training manual for the flight and air traffic controllers of civil aviation

Compiled by the teacher of the Ural UTC GA

Pozdnyakova V.A.

Yekaterinburg 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 Reasons for the formation of clouds. Cloud classification 12-13

4.2 Cloud observations 13

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

6.1 Air masses 16-17

6.2 Weather fronts 18

6.3 Warm front 18-19

6.4 Cold front 19-20

6.5 Occlusion fronts 20-21

6.6 Secondary edges 22

6.7 Upper warm front 22

6.8 Stationary fronts 22 7 Baric systems

7.1 Cyclone 23

7.2 Anticyclone 24

7.3 Movement and evolution of baric systems 25-26

8. High-rise frontal zones 26

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INTRODUCTION

Aviation meteorology studies 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 aircraft 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 is aware of the meteorological situation in the flight area, landing point and alternate airfields. Therefore, it is necessary that each pilot has a perfect command of the necessary meteorological knowledge, understands the physical essence of meteorological phenomena, their connection with the development of synoptic processes and local physical and geographical conditions, which is the key to flight safety.

The proposed training manual in a concise and accessible form sets out the concepts of the main meteorological quantities, phenomena, in connection with their impact on the work of aviation. The meteorological conditions of the flight are considered and practical recommendations are given on the most expedient actions of the flight crew in a difficult meteorological situation.

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: troposphere, stratosphere, mesosphere, thermosphere and exosphere.

Troposphere - extends from the earth's surface to a height of 10-12 km in temperate latitudes. At the poles it is lower, at the equator it is higher. About 79% of the total mass of the atmosphere and almost all of the water vapor is concentrated in the troposphere. Here, a decrease in temperature with height is observed, vertical air movements take place, westerly winds, clouds and precipitation are formed.

There are three layers in the troposphere:

a) Boundary (friction layer) - from the ground to 1000-1500 m. This layer affects the thermal and mechanical effects of the earth's surface. The daily variation of meteorological elements is observed. The lower part of the boundary layer up to 600 m thick is called the "surface layer". Here, the influence of the earth's surface is most pronounced, as a result of which such meteorological elements as temperature, air humidity, and wind experience sharp 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 up to a height of 6 km. In this layer, the influence of the earth's surface almost does not affect. Here, weather conditions are determined mainly by atmospheric fronts and vertical convective air currents.

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

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

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

The height of the tropopause depends on the temperature of the tropospheric air, i.e. from the latitude of the place, the 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 rises and approaches 0 degrees at the upper boundary of the stratosphere. It contains about 20% of the total mass of the atmosphere. Due to the low content of water vapor in the stratosphere, clouds do not form, with the rare exception of occasional mother-of-pearl clouds, consisting of the smallest supercooled water droplets. The winds are predominantly western, in summer above 20 km there is a transition to eastern 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 layer - the stratopause, which separates 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 height and reaches values ​​of about -90°.

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

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

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

1.1 Atmospheric research methods 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, indirect methods based on the study of geophysical phenomena occurring in the high layers of the atmosphere provide valuable information about the state of the high layers of the atmosphere.

Laboratory experiments and mathematical modeling are carried out (a system of formulas and equations that allow obtaining numerical and graphic information about the state of the atmosphere).

1.2 Standard atmosphere The movement of an aircraft in the atmosphere is accompanied by a complex interaction with the environment. The physical state of the atmosphere determines the aerodynamic forces arising in flight, the thrust force created by the engine, fuel consumption, speed and maximum allowable flight altitude, indications of aeronautical instruments (barometric altimeter, speed indicator, M number indicator), etc.

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

The atmosphere at all altitudes consists of dry air;

For zero height ("earth"), the mean sea level is taken, at which the air pressure is 760 mm Hg. Art. or 1013.25 hPa.

Temperature +15°С

Air density is 1.225kg/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 11km, 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 the gas corresponds to a certain speed of movement of molecules. The higher the average speed of the molecules, the higher the air temperature. Temperature characterizes the degree of air heating.

The following scales are adopted for the quantitative characteristics of temperature:

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

Fahrenheit. For the lower temperature of this scale, the temperature of the mixture of ice with ammonia (-17.8 ° C) is taken; for the upper temperature, the temperature of the human body. The gap is divided into 96 parts. T°(C)=5/9 (T°(F) -32).

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

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

The transfer of heat from the earth's surface to the atmosphere is carried out by the following main processes: thermal convection, turbulence, radiation.

1) Thermal convection is a vertical rise of air heated over certain parts of the earth's surface. The strongest development of thermal convection is observed in the daytime (afternoon) hours. Thermal convection can propagate 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 whirlwinds (from the Latin turbo whirlpool, whirlpool) that occur in a moving air stream due to its friction on the earth's surface and the internal friction of particles.

Turbulence contributes to the mixing of air, and hence the exchange of heat between the lower (heated) 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 of the heat received by the earth's surface as a result of the influx of 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, due to heat loss, cools. 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 leading role play: thermal convection and turbulence.

The temperature can change both horizontally along the earth's surface and vertically upwards. The value of the horizontal temperature gradient is expressed in degrees over a certain distance (111 km or 1 ° meridian). The larger the horizontal temperature gradient, the more hazardous phenomena(conditions) is formed in the transition zone, i.e. the activity of the atmospheric front increases.

The value that characterizes 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 the nature of the weather. According to ISA, y \u003d 0.65 ° / 100 m.

The layers of the atmosphere in which there is an increase in temperature with a height (y0 ° C) are called inversion layers.

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

Air temperature affects the flight of an aircraft. Aircraft takeoff and landing data largely depend on temperature. The length of the takeoff run and takeoff distance, the length of the run and landing distance decreases with decreasing temperature. The air density depends on the temperature, which determines the regime characteristics of the aircraft flight. As the temperature rises, the density decreases, and, consequently, the velocity head decreases and vice versa.

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

The temperature is taken into account when calculating the safe flight altitude. Very low temperatures complicate the operation of aviation equipment. At air temperatures close to 0 ° C and below, with supercooled precipitation, ice is formed, while flying in 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.

The air density determines the regime characteristics of the aircraft flight. Velocity is dependent on air density. The larger it is, the greater is the velocity head and, consequently, the greater is 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 in-ha = ------, 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 consequently, the velocity head decreases. As the temperature decreases, the opposite is observed.

A change in velocity head causes a change in engine thrust, lift, drag, and hence the horizontal and vertical speeds of the aircraft.

The length of the run and landing distance is inversely proportional to the density of the air and, consequently, to the temperature. A decrease in temperature by 15°C reduces the length of the run 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 amount of water vapor in the atmosphere and is expressed using the following basic characteristics.

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

Relative humidity - is characterized by the degree of saturation of the air with water vapor. Relative humidity is the percentage of the actual amount of water vapor contained in the air to the amount needed to be completely saturated 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. With an increase in relative humidity, there is a decrease in cloudiness, deterioration of visibility.

The dew point temperature is the temperature at which water vapor in air reaches 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 it is necessary to cool the air so that the vapor contained in it reaches a state of saturation. With dew point deficits of 3-4° or less, the air mass near the ground is considered humid, and fogs often occur at 0-1°.

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, which is emitted by the earth's surface and atmosphere, and thereby reduces the loss of heat from our planet. The main effect of humidity on the operation of aviation is through cloudiness, precipitation, fog, thunderstorms, and icing.

2.4 Atmospheric pressure Atmospheric air pressure is a 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. The change in pressure in space is closely related to the development of the main atmospheric processes. In particular, horizontal pressure inhomogeneity is the cause of air currents. Value atmospheric pressure measured in mm Hg.

millibars and hectopascals. There is a dependency between them:

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1 mmHg \u003d 1.33 mb \u003d 1.33 hPa 760 mm Hg. = 1013.25 hPa.

The change in pressure in the horizontal plane per unit of distance (1 ° of the meridian arc (111 km) or 100 km is taken per unit of distance) is called the horizontal baric gradient. It is always directed to the side. low pressure. The wind speed depends on the magnitude of the horizontal baric gradient, and the direction of the wind depends on its direction. In the northern hemisphere, the wind blows at an angle to the horizontal baric gradient, so that if you stand with your back to the wind, then 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 distinguish baric 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 surface synoptic weather maps, on which lines of equal baric trends are drawn - isallobars.

Atmospheric pressure decreases with height. In flight operations and flight management, it is necessary to know the change in altitude depending on the vertical pressure change.

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

To ensure flight safety, air pressure is transmitted to crews in the weather, reduced to the threshold level of the runway for a working start in mm Hg, mb, or pressure reduced to sea level for a standard atmosphere, depending on the type of aircraft.

The barometric altimeter on an aircraft 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. flight occurs at a constant pressure, then in fact the flight is carried out on an isobaric surface. The uneven occurrence of isobaric surfaces in height leads to the fact that the true flight altitude can differ significantly from the instrumental one.

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

2.5 Wind There is always horizontal movement of air in the atmosphere, called wind.

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/s, knots (1kt~0.5 m/s) and km/h (I m/s = 3.6 km/h).

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

According to 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, in AT1S and VHF weather reports. In reports distributed outside the aerodrome, the direction of the wind is indicated from the true meridian.

Averaging takes place 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 average speed in case of a difference of 3 m/s, if the wind is lateral (each airport has its own gradations), and in other cases after 5 m/s.

Squall - a sharp, sudden increase in wind that occurs for 1 minute or more, while the average speed differs by 8 m / s or more from the previous average speed and with a change in direction.

The duration of a 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 baric gradient force. The greater the pressure drop, the stronger the 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 surface layer) and above 1000-1500m has no effect. The friction force reduces the angle of deviation of the air flow from the direction of the horizontal baric gradient, i.e. 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 the low pressure will always be to the left of the flow. In practice, the wind at heights is predicted from baric topography maps.

The wind has a great influence on the flights of all types of aircraft. From the direction and speed of the wind in relation to the runway, the safety of the takeoff and landing of the aircraft depends. The wind affects the length of the takeoff and run of the aircraft. Dangerous and side wind, which causes the demolition of the aircraft. The wind causes dangerous phenomena that complicate flights, such as hurricanes, squalls, dust storms, snowstorms. The structure of the wind is turbulent, which causes turbulence and aircraft throws. When choosing an aerodrome runway, the prevailing wind direction is taken into account.

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

These include:

Breezes that are observed on the coast of the seas and large reservoirs, blowing on land from the water surface during the day and vice versa at night, they are respectively called sea and coastal breezes, the speed is 2-5 m / s, they spread vertically up to 500-1000 m. The reason for their occurrence uneven heating of water and land. Breezes affect the 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 mountainous. The vertical thickness of 1500 m often causes turbulence.

Föhn is a warm, dry wind that blows from the mountains into the valleys, sometimes reaching storm strength. The foehn effect is expressed in the region 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 an area of ​​high pressure, which contributes to the transshipment of air through the ridge. On the windward side, the rising air is cooled to the level of condensation (conditionally the lower boundary of the clouds) according to the dry adiabatic law (1 ° / 100 m.), Then according to the humid 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 ° / 100 m.). As a result, clouds are washed away from the lee side of the ridge and the air reaches the foot of the mountains very dry and warm. During the foehn, difficult weather conditions are observed on the windward side of the ridge (fog, precipitation) and cloudy weather on the leeward side of the ridge, but there is intense storm turbulence here.

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

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

A very strong bora is formed on Novaya Zemlya. On Lake Baikal, a bora-type wind forms at the mouth of the Sarma River and is locally called Sarma.

Afghan - A very strong, dusty west or southwest wind in the eastern Karakum, up the valleys of the Amu Darya, Syr Darya and Vakhsh rivers. Accompanied by dust storms and thunderstorms. Afghanets arises in connection with the frontal intrusions of cold within the Turan lowland.

Local winds, characteristic of certain areas, have a great influence on the work of aviation. Strengthening of the wind caused by the terrain features of the area makes it difficult to pilot the aircraft at low altitudes, and sometimes it is dangerous for the flight.

When the air stream crosses mountain ranges, lee waves are formed in the atmosphere. They occur when:

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

Gain in wind speed with height;

The presence of layers of inversion or isotherm from the top of the ridge for 1-3 km. The lee waves cause intense turbulence of aircraft. They are characterized by lenticular altocumulus clouds.

3.Vertical air movement

3.1 Causes and types of vertical air movements Vertical movements constantly occur in the atmosphere. They are playing essential role in such atmospheric processes as the vertical transfer of heat and water vapor, the formation of clouds and precipitation, the dissipation of clouds, the development of thunderstorms, the emergence 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. Warmer volumes of air, becoming lighter than the environment, rise up, giving way to denser cold air descending. The speed of ascending movements can reach several meters per second, and in individual cases 20-30m/s (in powerful cumulus, cumulonimbus clouds).

Downdrafts are smaller (~ 15 m/s).

Dynamic convection or dynamic turbulence - disordered vortex movements that occur during horizontal movement and friction of air on 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 zone of atmospheric fronts, in mountainous regions on the windward side, or a slow calm “settlement” 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 atmosphere causes an increase in pressure near the ground and downward vertical movements in this layer.

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

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

During flights in the air mass, where strongly developed vertical currents are observed, the aircraft experiences chatter and surges that complicate piloting. Large-scale vertical air currents can cause large vertical movements of the aircraft independent of the pilot. This can be especially dangerous when flying at altitudes close to the practical ceiling of the aircraft, where the updraft can lift the aircraft to a height much higher than the ceiling, or when flying in mountainous areas on the lee side of the ridge, where the downdraft can cause the aircraft to collide with the ground. .

Vertical air movements lead to the formation of cumulonimbus clouds dangerous for flights.

4.Clouds and precipitation

4.1 Reasons for the formation of clouds. Classification.

Clouds are visible accumulations of water droplets and ice crystals suspended in the air at a certain height above the earth's surface. Clouds form 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 the adiabatic (without heat exchange with the environment) decrease in temperature in the rising moist air, leading to the 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 size, the number of cloud particles per unit volume. Clouds are divided into ice, water and mixed (from crystals and drops).

According to international classification clouds by appearance are divided into 10 basic forms, and according to heights - into four classes.

1.Clouds upper tier- located at an altitude of 6000 m and above, they are thin white clouds, consist of ice crystals, have low water content, so they do not give precipitation. The power is small: 200 m - 600 m. These include:

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

Cirrocumulus / Cc- cirrocumulus / - small lambs, small white flakes, ripples. The flight is accompanied by a weak turbulence;

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

2. Clouds of the middle tier are located at a height from to

2km 6km, 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. Precipitation does not fall, the flight is accompanied by bumpiness, icing;

Altostratus / As-altostratus / are a continuous gray shroud, thin altostratus have a thickness of 300-600 m, dense - 1-2 km. In winter, heavy precipitation falls from them.

The flight is accompanied by icing.

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

Nimbostratus/Ns-nimbostratus/ having a dark gray color, high water content, give abundant precipitation. Under them, low fractonimbus/Frnb-fractonimbus/ clouds form 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 length is 2-3 km, often merging with high-stratus 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 the stratocumulus clouds the highest water content, here is the icing zone. Precipitation from these clouds, as a rule, does not fall;

Stratus clouds / St-stratus / are a continuous uniform cover hanging low above the ground with jagged blurry edges. The height is 100-150 m and below 100 m, and upper bound-300-800 m. Dramatically complicate take-off and landing, give drizzling precipitation. They can sink to the ground and turn into fog;

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

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

Cumulus clouds / Cu cumulus / - dense cloud masses developed vertically with white domed tops and with a flat base. Their lower limit is about 400-600 m and higher, the upper limit is 2-3 km, they do not give precipitation. Flight in them is accompanied by turbulence, 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, do not give precipitation. The flight in them is accompanied by moderate to strong turbulence, so it is forbidden to enter these clouds;

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 above. They are associated with thunderstorms, showers, hail, intense icing, intense turbulence, squalls, tornadoes, wind shifts. Cumulonimbus at the top look like an anvil, in the direction of which the cloud is shifting.

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 / Сu cong /

e) cumulonimbus /Cb/

2. Stratified arise as a result of ascending glides of warm humid air along the inclined surface of the cold, along the gentle frontal sections. These types of clouds include:

a) pinnately stratified/Cs/

b) high-layered /As/

c) stratified rain / Ns /

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

These include:

a) altocumulus undulate

b) stratocumulus undulate.

4.2 Observations of clouds When observing clouds, the following are determined: the total number of clouds (indicated in oktants.) the number of clouds of the lower tier, the shape of the clouds.

The height of the lower tier clouds is determined instrumentally using the light locator IVO, DVO 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.

In case of fog, precipitation or dust storm, when it is impossible to determine the base of the clouds, the results of instrumental measurements are indicated in the reports as vertical visibility.

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

Above elevated places, the clouds are located lower by 50-60% of the difference in the excess of the points themselves. Above woodlands 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, fractured-stratus, fractured rain is uneven, changeable and experiences significant fluctuations within 50-150 m.

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

4.3 Precipitation Water droplets or ice crystals that fall from clouds onto the Earth's surface are called precipitation. Precipitation usually falls from those clouds that are mixed in structure. For precipitation, it is necessary to enlarge drops or crystals up to 2-3 mm. The drops are enlarged due to their coalescence upon collision.

The second enlargement process 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 are in the range of -10°C-16°C and below. According to the nature of precipitation, precipitation is divided into 3 types:

Heavy precipitation - falls for a long time and over a large area from stratified and altostratus clouds;

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

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

By appearance they distinguish: rain, snow, freezing rain passing through the surface layer of air with a negative temperature, drizzle, croup, hail, snow grains, etc.

Precipitation includes: dew, hoarfrost, frost and blizzards.

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°С). Precipitation complicates the flight of an aircraft - worsens horizontal visibility. Precipitation is considered heavy when the visibility is less than 1000 m, regardless of the nature of the precipitation (following, torrential, drizzling). In addition, the water film on the cockpit windows 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. Hitting the hail zone causes serious technical damage. When landing on a wet runway, the length of the aircraft run changes, which can lead to overrunning the runway. A jet of water thrown off 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:

The meteorological visibility range / MLV / is the greatest distance from which, during daylight hours, it is possible to distinguish a black object against the sky near the horizon large sizes. At night, the distance to the most distant visible point source of light of a certain strength.

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

To monitor visibility at each aerodrome, a map of landmarks 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 readings.

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

Runway visual range /RVR/ - the visual range within which the pilot of an aircraft located on the runway center line 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 with the help of instruments or on boards on which single light sources (60 W light bulbs) are installed to assess visibility in the dark.

Since visibility can be very variable, visibility instruments are installed at the VTS on both courses and at the middle of the runway. The weather report includes:

a) runway length or less, the smaller of the two 2000m visibility measured at both ends of the runway;

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

At aerodromes where JVI lighting systems are used, with a visibility of 1500 m or less at dusk and at night, 1000 m or less during the day, recalculation is made according to the tables into the JVI visibility, which is also included in air weather. Recalculation of visibility into visibility of HMI only at night.

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

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

At a height of the lower cloud boundary of 100-150 m, it is equal to 40-50% of the horizontal; - at a height of 150-200 m, the slope 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 near the ground.

Fig.2 Effect of haze in the atmosphere on oblique visibility.

inversion

6. The main atmospheric processes that determine the weather Atmospheric processes observed over large geographic areas and studied using synoptic maps are called synoptic processes.

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

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

On the state of the air masses;

On the location of baric formations;

On the position of atmospheric fronts relative to the flight route.

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

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

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

a) arctic air (AB)

b) temperate/polar/air (HC)

d) tropical air (TV)

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

Depending on the thermal state (in relation to the underlying surface), air masses can be warm and cold.

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

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

The nature of the weather in the UWM 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 up to 1-2 km, cloudy above. In summer, cloudy weather or cumulus clouds with weak turbulence up to 500 m prevails in the UVM, visibility is somewhat worse due to dustiness.

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

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

In the cold season in NVM, there are no difficulties in flights. As a rule, it is clear, snow blowing, blowing snow, with north and northeast winds, and with a northwest intrusion of cold air, clouds are observed with a lower boundary of at least 200-300 m of the stratocumulus or cumulonimbus type with snow charges.

Secondary cold fronts can occur in the NVM. 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 ground towards the cold air.

The wind in front of the front at the surface of the earth turns to 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 ordered 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 with chatter, because. in this transition zone, two air masses move with different air densities, with different speeds and wind directions, which leads to the formation of eddies.

To assess the actual and expected weather conditions on the route or in the area of ​​flights, the 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 criteria:

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

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

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

The baric tendency is not the same on both sides of the front, it decreases in front of the front, increases behind the front, 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 front zone, the more active the weather. On high-altitude maps, the front is expressed in the condensation of isohypses and isotherms, in sharp contrasts in temperature and wind.

The front moves in the direction and with the speed of the gradient wind observed in cold air 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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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%, the share of others is less than 0.01%.

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

International standard atmosphere.

temperature gradient.

Air is heated by the ground, and density decreases with altitude. The combination of these two factors creates a normal situation of warmer air near the surface and gradually cooling with altitude.

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. If the air cools down, then it relative humidity approaches 100% and clouds begin to form.

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

Water can be in three forms: solid, liquid, gaseous. Water has a high heat capacity. In the solid state, it has a lower density than in the liquid state. As a result, it moderates the global climate. The gaseous state 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 a horizontal plane. This imbalance appears due to differences in air temperatures in adjacent areas or vertical air circulation in different areas. The root cause is solar heating of the surface.

The wind is named after the direction from which it blows. For example: the north blows from the north, the mountain - from the mountains, the valley - to 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 - to the left. The Coriolis effect is strongly pronounced at the poles and vanishes at the equator. The reason for the Coriolis effect is the rotation of the Earth under moving objects. This is not some real force, this is an illusion of right rotation for all freely moving bodies. Rice. 32

Air masses.

An air mass is called air having the same temperature and humidity, over a territory of at least 1600 km. The air mass can be cold if it was formed in the polar regions, warm - from the tropical zone. It can be marine or continental in terms of humidity.

When CWM arrives, the surface layer of air is heated from the ground, which increases instability. When TBM arrives, the ground 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 is moving forward, it is a cold front. If warm air moves forward - 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

Cloud types.

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

stratus cumulus cirrus Fig. 35

Classification of clouds by height:

Rice. 36

Lesser known clouds:

Haze - Formed when warm and humid air moves ashore, or when the earth radiates heat at night into a cold and humid layer.

Cloud cap - formed above the top when dynamic updrafts occur. Fig.37

Clouds in the form of a flag - formed behind the tops of mountains when strong wind. Sometimes it consists of snow. Fig.38

Rotor clouds - can form on the lee side of the mountain, behind the ridge in strong winds and have the form of long wisps located along the mountain. They form on the ascending sides of the rotor and collapse on the descending ones. Indicate severe turbulence. Fig. 39

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

Rice. 37 Fig. 38 Fig.39

Ribbed clouds - very similar to ripples on the water. Formed when one air layer moving 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 an inversion layer. Rice. 42

Rice. 40 Fig. 41 Fig. 42

Cloud formation.

Clouds are made up of countless microscopic water particles of various sizes, from 0.001 cm in saturated air to 0.025 cm with continued condensation. The main way clouds form in the atmosphere is through the cooling of moist air. This happens when the air cools as it rises.

Fog forms in cooling air from contact with the ground.

Upstreams.

There are three main causes of updrafts. 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 lifting speed depends on the strength of the wind and the steepness of the slope, it can reach up to 30 m/s. Thermal flow occurs when lifting more warm air, which in sunny days heated by the earth's surface. 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. Assume that the rising air is cooled in a certain way, for example, 1 0 С/100 m. But the dew point drops only by 0.2 0 С/100 m. Thus, the dew point and the temperature of the rising air converge by 0.8 0 С/100 m. When they equalize, clouds will form. Meteorologists use dry and wet bulbs to measure ground and saturation temperatures. From these measurements, you can calculate the base of the clouds. 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 2000m.

Cloud life.

Clouds during their development 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 to decay into an amorphous mass. However, often the clouds do not break up as quickly. This occurs when the air humidity is at cloud level and cloud level is the same. 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 lexicon of airmen.

Continuing thermals can also feed individual clouds, increasing their lifetime by more than 0.5 hours. In fact, thunderstorms are long-lived clouds formed by thermal flows.

Precipitation.

Precipitation requires two conditions: continuous updrafts and high humidity. In the cloud, water droplets or ice crystals begin to grow. When they get big, they start to fall. It is snowing, raining or hail.

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4. Local signs of weather

6. Aviation weather forecast

1. Atmospheric phenomena dangerous for aviation

Atmospheric phenomena are important element weather: whether it is raining or snowing, whether there is fog or a dust storm, whether a blizzard or thunderstorm is raging, both the perception of the current state of the atmosphere by living beings (humans, animals, plants) and the effect of weather on those under open-air machines and mechanisms, buildings, roads, etc. Therefore, observations of atmospheric phenomena (their correct definition, fixing the start and end times, intensity fluctuations) on a network of weather stations are of great importance. Atmospheric phenomena have a great influence on the activity civil aviation.

Ordinary weather conditions on Earth it is wind, clouds, precipitation(rain, snow, etc.), fog, thunderstorms, dust storms and snowstorms. Rarer occurrences include natural disasters such as tornadoes and hurricanes. The main consumers of meteorological information are the navy and aviation.

Atmospheric phenomena hazardous to aviation include thunderstorms, squalls (wind gusts of 12 m/s and above, storms, hurricanes), fog, icing, heavy precipitation, hail, blizzards, dust storms, and low clouds.

A thunderstorm is a phenomenon of cloud formation, accompanied by electrical discharges in the form of lightning and precipitation (sometimes hail). The main process in the formation of thunderstorms is the development of cumulonimbus clouds. The base of the clouds reaches an average height of 500 m, and the upper limit can reach 7000 m or more. In thunderclouds, strong vortex air movements are observed; grain, snow, hail are observed in the middle part of the clouds, and a snow blizzard is observed in the upper part. Thunderstorms are usually accompanied by squalls. Distinguish between intramass and frontal thunderstorms. Frontal thunderstorms develop mainly on cold atmospheric fronts, less often on warm ones; the band of these thunderstorms is usually narrow in width, but along the front it covers an area of ​​up to 1000 km; observed day and night. Thunderstorms are dangerous with electric discharges and strong turbulence; A lightning strike on an aircraft can lead to serious consequences. During a severe thunderstorm, you cannot use radio communications. Flying in the presence of thunderstorms is extremely difficult. Cumulonimbus clouds must be avoided from the side. Less vertically developed thunderclouds can be overcome from above, but at a significant excess. In exceptional cases, the intersection of thunderstorm zones can be carried out through small breaks of cloudiness occurring in these zones.

A squall is a sudden increase in wind with a change in its direction. Flurries usually occur during the passage of sharply pronounced cold fronts. The width of the squall zone is 200-7000 m, the height is up to 2-3 km, the length of the front is hundreds of kilometers. Wind speed during squalls can reach 30-40 m/s.

Fog is a phenomenon of condensation of water vapor in the surface layer of air, in which the visibility range is reduced to 1 km or less. At a visibility range of more than 1 km, condensation haze is called haze. According to the formation conditions, fogs are divided into frontal and intramass. Frontal fogs are more common when passing warm fronts and they are very dense. Intramass fogs are divided into radiation (local) and adventive (moving cooling fogs).

Icing is the accumulation of ice on various parts aircraft. The cause of icing is the presence of water droplets in the atmosphere in a supercooled state, i.e., with temperatures below 0 ° C. The collision of droplets with an aircraft leads to their freezing. The build-up of ice increases the weight of the aircraft, reduces its lift, increases drag, etc.

Icing is of three types:

b deposition of pure ice (most dangerous view icing) is observed when flying in clouds, precipitation and fog at temperatures from 0 ° to -10 ° C and below; deposition occurs primarily on the frontal parts of the aircraft, cables, tail unit, in the nozzle; ice on the ground is a sign of the presence of significant icing zones in the air;

hoarfrost - a whitish, granular coating - a less dangerous type of icing, occurs at temperatures up to -15 - -20 ° C and lower, settles more evenly on the surface of the aircraft and does not always hold tightly; a long flight in a frost zone is dangerous;

Frost is observed at fairly low temperatures and does not reach dangerous sizes.

If icing began while flying in clouds, then it is necessary:

b if there are breaks in the clouds, fly through these breaks or between layers of clouds;

b if possible - go to an area with a temperature above 0 °;

b if it is known that the temperature near the ground is below 0 ° and the height of the clouds is negligible, then it is necessary to gain altitude in order to get out of the clouds or get into a layer with lower temperatures.

If icing began while flying in supercooled rain, then it is necessary:

b fly into a layer of air with a temperature above 0 °, if the location of such a layer is known in advance;

leave the rain zone, and in case of threatening icing, return or land at the nearest airfield.

A blizzard is a phenomenon of snow being carried by the wind in a horizontal direction, often accompanied by whirling movements. Visibility in snowstorms can drop sharply (up to 50–100 m or less). Blizzards are characteristic of cyclones, the periphery of anticyclones, and fronts. They make it difficult to land and take off the aircraft, sometimes making them impossible.

Mountainous regions are characterized by sudden changes in the weather, frequent cloud formations, precipitation, thunderstorms, and changing winds. In the mountains, especially in the warm season, there is a constant upward and downward movement of air, and air whirlwinds appear near the slopes of the mountains. Mountain ranges are mostly covered with clouds. During the day and in summer they are cumulus clouds, and at night and in winter they are low stratus clouds. Clouds form primarily over mountain tops and on their windward side. Powerful cumulus clouds over mountains are often accompanied by heavy downpours and thunderstorms with hail. It is dangerous to fly near mountain slopes, as the aircraft can get caught in air vortices. The flight over the mountains must be carried out in excess of 500-800 m, after the flight of the mountains (peaks) you can start descending at a distance of 10-20 km from the mountains (peaks). Flight under the clouds can be relatively safe only if the lower boundary of the clouds is located at an altitude of 600-800 m above the mountains. If this limit is lower than the indicated height and if the tops of the mountains are closed in places, then the flight becomes more difficult, and with a further decrease in the clouds it becomes dangerous. In mountainous conditions, it is possible to break through the clouds upwards or fly in the clouds using instruments only with excellent knowledge of the flight area.

2. Effect of clouds and precipitation on flight

aviation weather atmospheric

Influence of clouds on flight.

The nature of the flight is often determined by the presence of cloudiness, its height, structure and extent. Cloudiness complicates the piloting technique and tactical actions. Flight in the clouds is difficult, and its success depends on the availability of appropriate flight and navigation equipment on the aircraft and on the training of the flight crew in instrument piloting. In cumulus clouds, flight (especially on heavy aircraft) is complicated by high air turbulence, in cumulonimbus, in addition, the presence of thunderstorms.

In the cold season, and at high altitudes and in summer period, when flying in clouds, there is a risk of icing.

Table 1. The value of visibility in the clouds.

Effect of precipitation on flight.

The influence of precipitation on flight is mainly due to the phenomena accompanying it. Heavy precipitation (especially drizzle) often takes large areas, are accompanied by low clouds and greatly impair visibility; in the presence of supercooled drops in them, icing of the aircraft occurs. Therefore, in heavy precipitation, especially at low altitudes, flight is difficult. In showers of a frontal nature, flight is difficult due to a sharp deterioration in visibility and increased wind.

3. Responsibilities of the aircraft crew

Before departure, the aircraft crew (pilot, navigator) must:

1. Listen to a detailed report of the duty meteorologist on the state and weather forecast along the route (area) of the flight. In this case, special attention should be paid to the presence along the route (area) of the flight:

l atmospheric fronts, their position and intensity, vertical power of frontal cloud systems, direction and speed of front movement;

l zones with dangerous weather phenomena for aviation, their boundaries, direction and speed of displacement;

Ways to bypass areas with bad weather.

2. Obtain a weather bulletin from the weather station, which should include:

ь actual weather along the route and at the point of landing not more than two hours ago;

l weather forecast along the route (area) and at the landing point;

l vertical section of the expected state of the atmosphere along the route;

l astronomical data of points of departure and landing.

3. If the departure is more than an hour late, the crew must hear the report of the meteorologist on duty again and receive a new weather bulletin.

In flight, the aircraft crew (pilot, navigator) must:

1. Observe the state of the weather, especially for phenomena that are dangerous for flight. This will allow the crew to timely notice a sharp deterioration in the weather along the route (area) - flights, correctly assess it, make an appropriate decision for a further flight and complete the task.

2. Request information about the meteorological situation in the landing area, as well as barometric pressure data at the aerodrome level, 50–100 km before approaching the airfield, and set the obtained barometric pressure value on the onboard altimeter.

4. Local signs of weather

Signs of persistent good weather.

1. High blood pressure, rising slowly and steadily over several days.

2. The correct daily course of the wind: it is quiet at night, during the day there is a significant increase in wind; on the shores of the seas and large lakes, as well as in the mountains, the correct change of winds: 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, the sky is clear, and only in the evening when there is calm, thin stratus clouds can float. In summer, on the contrary: cumulus clouds develop during the day and disappear in the evening.

4. The correct daily course of temperature (increase during the day, decrease at night). Temperatures are low in winter and high in summer.

5. No precipitation; heavy dew or frost at night.

6. Ground mists disappearing after sunrise.

Signs of persistent bad weather.

1. Low pressure, changing little or even more decreasing.

2. Lack of normal daily wind patterns; wind speed is significant.

3. The sky is completely covered with stratified rain or stratus clouds.

4. Long rains or snowfalls.

5. Minor temperature changes during the day; Relatively warm in winter, cool in summer.

Signs of bad weather.

1. pressure drop; the faster the pressure drops, the sooner the weather will change.

2. The wind intensifies, its daily fluctuations almost disappear, the direction of the wind changes.

3. Cloudiness increases, and the following order of appearance of clouds is often noticed: cirrus appears, then cirrostratus (their movement is so fast that it is noticeable to the eye), cirrostratus is replaced by high-stratus, and the latter - stratified rain.

4. Cumulus clouds do not dissipate and do not disappear by evening, and their number even increases. If they take the form of towers, then thunderstorms are to be expected.

5. The temperature rises in winter, while in summer there is a noticeable decrease in its daily variation.

6. Colored circles and crowns appear around the Moon and Sun.

Signs of better weather.

1. Pressure rises.

2. Cloudiness becomes changing, gaps appear, although at times the entire sky can still be covered with low rain clouds.

3. Rain or snow falls from time to time and is quite heavy, but there is no continuous fall of them.

4. The temperature drops in winter, rises in summer (after a preliminary decrease).

5. Examples of aircraft crashes due to atmospheric phenomena

On Friday, an FH-227 turboprop aircraft of the Uruguayan Air Force carried the Old Christians junior rugby team from Montevideo, Uruguay, through the Andes, to a match in the Chilean capital of Santiago.

The flight began the day before, on October 12, when the flight took off from Carrasco Airport, but due to bad weather, the plane landed at the airport in Mendoza, Argentina and stayed there overnight. The plane was unable to fly directly to Santiago due to the weather, so the pilots had to fly south parallel to the Mendoza mountains, then turn west, then head north and begin their descent towards Santiago after passing Curico.

When the pilot reported the passage of Curico, the air traffic controller cleared the descent to Santiago. This was a fatal mistake. The plane flew into the cyclone and began to descend, focusing only on time. When the cyclone was passed, it became clear that they were flying straight to the rock and there was no way to avoid the collision. As a result, the plane caught the top of the peak with its tail. Due to impacts on the rocks and the ground, the car lost its tail and wings. The fuselage rolled at great speed down the slope until it crashed nose into blocks of snow.

More than a quarter of the passengers died in the fall and collision with a rock, several more died later from wounds and cold. Then, out of the remaining 29 survivors, another 8 died during an avalanche.

The crashed plane belonged to the special transport aviation regiment of the Polish Army, which served the government. Tu-154-M was assembled in the early 1990s. The plane of the President of Poland and the second of the same government Tu-154 from Warsaw were undergoing scheduled repairs in Russia, in Samara.

Information about the tragedy that broke out this morning on the outskirts of Smolensk still has to be collected bit by bit. The plane of the President of Poland Tu-154 came in for landing in the area of ​​the airfield "Severny". This is a first-class airstrip, there were no complaints about it, but at this hour the military airfield did not receive aircraft due to non-flying weather. The hydrometeorological center of Russia predicted heavy fog the day before, visibility 200-500 meters, these are very bad conditions for landing, on the verge of a minimum even for the best airports. Some ten minutes before the tragedy, the dispatchers deployed a Russian transporter to an alternate site.

Of those who were on board the Tu-154, no one escaped.

The plane crash occurred in northeast China - according to various estimates, about 50 people survived, and more than 40 died. A Henan Airlines plane flying from Harbin, while landing in the city of Yichun, “skipped” the runway in heavy fog, fell apart on impact and caught fire.

There were 91 passengers and five crew members on board. The victims were taken to the hospital with fractures and burns. Most are in a relatively stable condition, nothing threatens their lives. Three are in critical condition.

6. Aviation weather forecast

In order to avoid aircraft crashes due to atmospheric phenomena, aviation weather forecasts are developed.

The development of aviation weather forecasts is a complex and interesting branch of synoptic meteorology, and the responsibility and complexity of such work is much higher than in the preparation of ordinary general use forecasts (for the public).

The source texts of aerodrome weather forecasts (code form TAF - Terminal Aerodrome Forecast) are published in the form in which they are compiled by the meteorological services of the respective airports and transferred to worldwide network exchange of meteorological information. It is in this form that they are used for consultations with the air traffic control staff of airports. These forecasts are the basis for the analysis of the expected meteorological conditions at the point of landing and the decision by the crew commander to take off.

The weather forecast for the aerodrome is made every 3 hours for the period from 9 to 24 hours. As a rule, forecasts are issued at least 1 hour and 15 minutes in advance before the start of their validity period. In case of sharp, previously unpredicted weather changes, an extraordinary forecast (adjustment) may be issued, its lead time may be 35 minutes before the start of the validity period, and the validity period may differ from the standard one.

Time in aviation forecasts is indicated according to Greenwich Mean Time (Universal Time - UTC), to get Moscow time you need to add 3 hours to it (during summer time - 4 hours). The name of the aerodrome is followed by the day and time of the forecast (for example, 241145Z - on the 24th at 11-45), then the day and period of validity of the forecast (for example, 241322 - on the 24th from 13 to 22 hours; or 241212 - on the 24th of from 12:00 to 12:00 of the next day; for extraordinary forecasts, minutes can also be indicated, for example, 24134022 - on the 24th from 13:40 to 22:00).

An aerodrome weather forecast includes the following elements (in order):

b wind - direction (where it blows from, in degrees, for example: 360 - north, 90 - east, 180 - south, 270 - west, etc.) and speed;

ь horizontal visibility range (usually in meters, in the USA and some other countries - in miles - SM);

l weather phenomena;

L cloudiness by layers - the amount (clear - 0% of the sky, separate - 10-30%, scattered - 40-50%, significant - 60-90%; solid - 100%) and the height of the lower boundary; in case of fog, blizzard and other phenomena, vertical visibility may be indicated instead of the lower boundary of the clouds;

l air temperature (indicated only in some cases);

the presence of turbulence, icing.

Note:

Responsibility for the accuracy and justification of the forecast lies with the forecasting engineer who developed this forecast. In the West, when compiling aerodrome forecasts, the data of global computer modeling of the atmosphere are widely used, the weather forecaster only makes minor adjustments to these data. In Russia and the CIS, aerodrome forecasts are developed mainly manually, using labor-intensive methods (analysis of synoptic maps, taking into account local aeroclimatic conditions), and therefore the accuracy and validity of forecasts is lower than in the West (especially in a complex, rapidly changing synoptic situation).

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It is very weather dependent: snow, rain, fog, low clouds, strong gusty wind and even complete calm are unfavorable conditions for a 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, rising slowly and steadily over several days.
2. The correct daily course of the wind: quiet at night, during the day a significant increase in wind; on the shores of the seas and large lakes, as well as in the mountains, the correct change of winds:
   • by day - from water to land and from valleys to peaks,
   • at night - from land to water and from peaks to valleys.
3. In winter, the sky is clear, and only in the evening when there is calm, thin stratus clouds can float. In summer, on the contrary: cumulus clouds develop and disappear in the evening.
4. The correct daily course of temperature (increase during the day, decrease at night). Temperatures are low in winter and high in summer.
5. There are no precipitations; heavy dew or frost at night.
6. Surface mists disappearing after sunrise.

Signs of persistent bad weather

1. Low pressure, changing little or falling even more.
2. Lack of normal daily wind patterns; wind speed is significant.
3. The sky is completely overcast with nimbostratus or stratus clouds.
4. Continuous rain or snowfall.
5. Minor changes in temperature during the day; Relatively warm in winter, cool in summer.

Signs of bad weather

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

Signs of better weather

1. The pressure is rising.
2. Cloudiness becomes changing, gaps appear, although at times the entire sky can still be covered with low rain clouds.
3. Rain or snow falls from time to time and is quite heavy, but they do not fall continuously.
4. The temperature drops in winter and rises in summer (after a preliminary decrease).

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. With the development of aviation (the creation of new types of aircraft, the expansion of the range of altitudes and flight speeds, the scale of territories for performing flights, the expansion of the range of tasks solved with the help of aircraft, etc.), before M. a. new tasks are set. The creation of new airports and the opening of new air routes require climate research in the areas of proposed construction and in the free atmosphere along the planned flight routes in order to select the optimal solutions to the tasks set. Changing conditions around already existing airports (as a result of human activities or under the influence of natural physical processes) requires constant study of the climate of existing airports. The close dependence of the weather near the earth's surface (aircraft takeoff and landing zone) on local conditions requires special studies for each airport and the development of methods for forecasting takeoff and landing conditions for almost every airport. The main tasks of M. and. as an applied discipline - increasing the level and optimization of information support for flights, improving the quality of the meteorological services provided (accuracy of actual data and justification of forecasts), and increasing efficiency. The solution of these problems is achieved by improving the material and technical base, technologies and methods of observation, in-depth study of the physics of the processes of formation of weather phenomena important for aviation and improving the methods for forecasting these phenomena.

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

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