MINISTRY OF HIGHER AND SECONDARY SPECIAL EDUCATION OF THE REPUBLIC OF UZBEKISTAN

TASHKENT STATE AVIATION INSTITUTE

Department: "Air Traffic Control"

Lecture notes

course "Aviation meteorology"

TASHKENT - 2005

"Aviation meteorology"

Tashkent, TGAI, 2005.

The lecture notes include basic information about meteorology, atmosphere, winds, clouds, precipitation, synoptic weather maps, baric topography maps and radar conditions. The movement and transformation of air masses, as well as pressure systems, are described. The issues of movement and evolution of atmospheric fronts, occlusion fronts, anticyclones, blizzards, types and forms of icing, thunderstorms, lightning, atmospheric turbulence and regular traffic - METAR, international aviation code TAF are considered.

Lecture notes were discussed and approved at a meeting of the Air Traffic Control Department

Method approved by the FGA council at a meeting

Lecture No. 1

1. The subject and significance of meteorology:

2. Atmosphere, composition of the atmosphere.

3. The structure of the atmosphere.

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

Under the weather commonly understood physical condition atmosphere at any moment or period of time. Weather is characterized by a combination of meteorological elements and phenomena, such as atmospheric pressure, wind, humidity, air temperature, visibility, precipitation, clouds, icing, ice, fog, thunderstorms, blizzards, dust storms, tornadoes, various optical phenomena (halos, crowns) .

Climate – long-term weather regime: characteristic of a given place, developing under the influence of solar radiation, the nature of the underlying surface, atmospheric circulation, changes in the earth and atmosphere.

Aviation meteorology studies meteorological elements and atmospheric processes from the point of view of their influence on aviation technology and aviation activities, and also develops methods and forms of meteorological support for flights. Correct consideration of meteorological conditions in each specific case to best ensure the safety, economy and efficiency of flights depends on the pilot and dispatcher, on their ability to use meteorological information.

Flight and dispatch personnel must know:

What exactly is the influence of individual meteorological elements and weather phenomena on the operation of aviation;

Good understanding of physics atmospheric processes, creating various conditions weather and their changes in time and space;

Know the methods of operational meteorological support of flights.

Organization of civil aviation aircraft flights on a scale globe, and meteorological support for these flights is unthinkable without international cooperation. There are international organizations that regulate the organization of flights and their meteorological support. These are ICAO (International Civil Aviation Organization) and WMO (World Meteorological Organization), which closely cooperate with each other on all issues of collection and dissemination of meteorological information for the benefit of civil aviation. Cooperation between these organizations is governed by special working agreements concluded between them. ICAO determines the meteorological information requirements arising from GA requests, and WMO determines the scientifically sound possibilities for meeting them and develops recommendations and regulations, as well as various guidance materials, mandatory for all its member countries.

Atmosphere.

Atmosphere is the air envelope of the earth, consisting of a mixture of gases and colloidal impurities ( dust, drops, crystals).

The earth is like the bottom of a huge ocean of air, and everything living and growing on it owes its existence to the atmosphere. It delivers the oxygen necessary for breathing, protects us from deadly cosmic rays and ultraviolet radiation from the sun, and also protects the earth's surface from extreme heating during the day and extreme cooling at night.

In the absence of an atmosphere, the surface temperature of the globe would reach 110° or more during the day, and at night it would sharply drop to 100° below zero. There would be complete silence everywhere, since sound cannot travel in emptiness, day and night would change instantly, and the sky would be completely black.

The atmosphere is transparent, but it constantly reminds us of itself: rain and snow, thunderstorms and blizzards, hurricanes and calm, heat and frost - all this is a manifestation of atmospheric processes occurring under the influence of solar energy and during the interaction of the atmosphere with the very surface of the earth.

Composition of the atmosphere.

Up to an altitude of 94-100 km. the percentage composition of the air remains constant - the homosphere (“homo” from Greek is the same); nitrogen – 78.09%, oxygen – 20.95%, argon – 0.93%. In addition, the atmosphere contains a variable amount of other gases (carbon dioxide, water vapor, ozone), solid and liquid aerosol impurities (dust, industrial gases, smoke, etc.).

The structure of the atmosphere.

Data from direct and indirect observations show that the atmosphere has a layered structure. Depending on what physical property of the atmosphere (temperature distribution, air composition at altitudes, electrical characteristics) is the basis for division into layers, there are a number of schemes for the structure of the atmosphere.

The most common scheme for the structure of the atmosphere is a scheme based on the vertical temperature distribution. According to this scheme, the atmosphere is divided into five main spheres or layers: the troposphere, stratosphere, mesosphere, thermosphere and exosphere.

		Interplanetary outer space
Upper limit of the geocorona
		Exosphere (Sphere of Scattering)
Thermopause
		Thermosphere (ionosphere)
Mesopause
Mesosphere
Stratopause
Stratosphere
Tropopause
Troposphere
The table shows the main layers of the atmosphere and their average heights in temperate latitudes. Test questions. 1. What does aviation meteorology study? 2. What functions are assigned to IKAO, WMO?

3. What functions are assigned to the Glavhydromet of the Republic of Uzbekistan?

4. Characterize the composition of the atmosphere.

Lecture No. 2.

1. The structure of the atmosphere (continued).

2. Standard atmosphere.

Troposphere – the lower part of the atmosphere to an average altitude of 11 km, where 4/5 of the total mass is concentrated atmospheric air and almost all water vapor. Its height varies depending on the latitude of the place, time of year and day. It is characterized by an increase in temperature with height, an increase in wind speed, and the formation of clouds and precipitation. There are 3 layers in the troposphere:

1. Boundary (friction layer) - from the ground to 1000 - 1500 km. This layer is affected by thermal and mechanical effects earth's surface. The daily cycle of meteorological elements is observed. The lower part of the boundary layer, 600 m thick, is called the “ground layer”. The atmosphere above 1000 - 1500 meters is called the “free atmosphere layer” (without friction).

2. The middle layer is located from the upper boundary of the boundary layer to a height of 6 km. There is almost no influence of the earth's surface here. Weather conditions depend on atmospheric fronts and the vertical balance of air masses.

3. The top layer lies above 6 km. and extends to the tropopause.

Tropopause – transition layer between the troposphere and stratosphere. The thickness of this layer ranges from several hundred meters to 1 – 2 km, and average temperature from minus 70° - 80° in the tropics.

The temperature in the tropopause layer can remain constant or increase (inversion). In this regard, the tropopause is a powerful delay layer for vertical air movements. When crossing the tropopause at the flight level, changes in temperature, changes in moisture content and air transparency can be observed. The minimum wind speed is usually located in the tropopause zone or its lower boundary.

Very weather dependent: snow, rain, fog, low clouds, strong gusty winds 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 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 the seas and large lakes, and also 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 it is calm can thin stratus clouds appear. 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 the temperature is low, in summer it is high.
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 daily wind patterns; 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 there are breaks, 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).

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. 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, 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 according to 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 the 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 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 the 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 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. Let us 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 converge by 0.8 0 C/100 m. When they become equal, 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. It is snowing, raining or hailing.

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4. Local signs weather

6. Aviation weather forecast

1. Atmospheric phenomena dangerous to aviation

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

Common weather phenomena on Earth are 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 navy and aviation.

Atmospheric phenomena dangerous to aviation include thunderstorms, squalls (wind gusts of 12 m/sec and above, storms, hurricanes), fog, icing, rainfall, hail, blizzards, dust storms, 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. Strong vortex air movements are observed in thunderclouds; In the middle part of the clouds, pellets, snow, and hail are observed, and in the upper part there is a blizzard. Thunderstorms are usually accompanied by squalls. There are 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 due to electrical discharges and strong vibrations; A lightning strike on an airplane can lead to serious consequences. During a severe thunderstorm, radio communications should not be used. Flights in the presence of thunderstorms are extremely difficult. Cumulonimbus clouds must be avoided from the side. Less vertically developed thunderclouds can be overcome from above, but at a significant elevation. In exceptional cases, the intersection of thunderstorm zones can be accomplished through small cloud breaks found in these zones.

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

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

Icing is the phenomenon of ice deposits on various parts of an 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 airplane leads to their freezing. Ice buildup increases the weight of the aircraft, reduces its lift, increases drag etc.

There are three types of icing:

b deposition of pure ice (the most dangerous type of 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 surfaces, and in the nozzle; ice on the ground is a sign of the presence of significant icing zones in the air;

b frost - a whitish, granular coating - a less dangerous type of icing, it occurs at temperatures up to -15--20 ° C and below, settles more evenly on the surface of the aircraft and does not always hold tightly; a long flight in an area that produces frost is dangerous;

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

If icing begins while flying in the clouds, you must:

b if there are breaks in the clouds, fly through these gaps 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 insignificant, then it is necessary to gain altitude in order to leave the clouds or get into a layer with lower temperatures.

If icing began while flying in freezing rain, you must:

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

b leave the rain zone, and if the icing is threatening, return or land at the nearest airfield.

A blizzard is a phenomenon of snow being transported by the wind in a horizontal direction, often accompanied by vortex movements. Visibility in snowstorms can decrease sharply (to 50-100 m or less). Blizzards are typical for cyclones, the periphery of anticyclones and fronts. They make it difficult for an airplane to land and take off, sometimes making it impossible.

Mountainous areas are characterized by sudden changes in weather, frequent cloud formations, precipitation, thunderstorms, and changing winds. In the mountains, especially in the warm season, there is constant upward and downward movement of air, and near the slopes of the mountains there are air vortices. The mountain ranges are mostly covered with clouds. During the day and in the summer it is cumulus clouds, and at night and in winter - low stratus clouds. Clouds form primarily over the tops of mountains and on their windward side. Powerful cumulus clouds over the mountains are often accompanied by heavy showers and thunderstorms with hail. Flying near mountain slopes is dangerous, as the plane can get caught in air vortices. The flight over the mountains must be carried out at an altitude of 500-800 m; the descent after flying over the mountains (peaks) can begin at a distance of 10-20 km from the mountains (peaks). Flying under 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 specified altitude and if the mountain tops are closed in places, then the flight becomes more difficult, and with further decrease in clouds it becomes dangerous. In mountainous conditions, breaking through the clouds upward or flying through the clouds using instruments is possible only with excellent knowledge of the flight area.

2. Effect of clouds and precipitation on flight

aviation weather atmospheric

The influence of clouds on flight.

The nature of the flight is often determined by the presence of clouds, its height, structure and extent. Cloudiness complicates 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 techniques. In powerful cumulus clouds, flying (especially on heavy aircraft) is complicated by high air turbulence; in cumulonimbus clouds, in addition, the presence of thunderstorms.

IN cold period year, and at high altitudes and in the summer, when flying in the clouds, there is a danger of icing.

Table 1. Cloud visibility value.

Effect of precipitation on flight.

The influence of precipitation on flight is mainly due to the phenomena accompanying it. Covering precipitation (especially drizzle) often covers large areas, is accompanied by low clouds and greatly impairs visibility; If there are supercooled droplets in them, icing of the aircraft occurs. Therefore, in heavy precipitation, especially at low altitudes, flight is difficult. In frontal rainfall, 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. Hear a detailed report from the meteorologist on duty about the condition and weather forecast along the flight route (area). In this case, special attention should be paid to the presence along the flight route (area):

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

b zones with hazardous weather phenomena for aviation, their boundaries, direction and speed of displacement;

b ways to avoid areas with bad weather.

2. Receive a weather bulletin from the weather station, which should indicate:

b actual weather along the route and at the landing point no more than two hours ago;

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

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

b astronomical data of departure and landing points.

3. If the departure is delayed by more than an hour, the crew must listen again to the report of the duty meteorologist and receive a new weather bulletin.

During the flight, the aircraft crew (pilot, navigator) is obliged to:

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

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

4. Local weather signs

Signs of persistent good weather.

1. High blood pressure, slowly and continuously increasing 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, there is a regular 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 it is calm, thin stratus clouds can float. In summer, it’s the opposite: cumulus clouds develop during the day and disappear in the evening.

4. Correct daily temperature variation (increase during the day, decrease at night). In the winter half of the year the temperature is low, in the summer it is high.

5. 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 daily wind patterns; wind speed is significant.

3. The sky is completely covered with nimbostratus or stratus clouds.

4. Long rains or snowfalls.

5. Minor changes in temperature 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 cirrostratus.

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. 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 decreases in winter and increases in summer (after a preliminary decrease).

5. Examples of aircraft crashes due to atmospheric phenomena

On Friday, a Uruguayan Air Force FH-227 turboprop carried the Old Christians junior rugby team from Montevideo, Uruguay, across the Andes for 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 remained there overnight. The plane was unable to fly directly to Santiago due to weather, so the pilots had to fly south parallel to the Mendoza Mountains, then turn west, then head north and begin their descent to Santiago after passing through Curico.

When the pilot reported passing Curico, the air traffic controller cleared the descent to Santiago. This was a fatal mistake. The plane flew into a cyclone and began to descend, guided only by time. When the cyclone was passed, it became clear that they were flying straight onto 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 with rocks and the ground, the car lost its tail and wings. The fuselage rolled at great speed down the slope until it crashed nose-first into blocks of snow.

More than a quarter of the passengers died when they fell and collided with a rock, and several more died later from wounds and cold. Then, of the remaining 29 survivors, 8 more died in an avalanche.

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

Information about the tragedy that took place this morning on the outskirts of Smolensk still has to be collected bit by bit. The Polish President's Tu-154 plane was landing near the Severny airfield. This is a first-class runway and there were no complaints about it, but at that hour the military airfield was not accepting planes due to bad 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, dispatchers deployed a Russian transporter to a reserve site.

None of those on board the Tu-154 survived.

The plane crash occurred in northeast China - according to various estimates, about 50 people survived and more than 40 died. The Henan Airlines plane, flying from Harbin, overshot the runway in heavy fog when landing in the city of Yichun, broke into pieces 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. The majority are in a relatively stable condition, their lives are not in danger. 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 conventional forecasts public use(for the population).

The source texts of airport weather forecasts (code form TAF - Terminal Aerodrome Forecast) are published as they are compiled by the weather services of the corresponding airports and transmitted to the worldwide weather information exchange network. It is in this form that they are used for consultations with airport flight control personnel. These forecasts are the basis for analyzing the expected weather conditions at the landing point and making a decision for departure by the crew commander.

The weather forecast for the airfield is compiled every 3 hours for a period from 9 to 24 hours. As a rule, forecasts are issued at least 1 hour 15 minutes before the start of their validity period. In case of sudden, 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 in Greenwich Mean Time (Universal Time - UTC), to obtain Moscow time you must add 3 hours to it (during summer time - 4 hours). The name of the airfield 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 from 12 o'clock to 12 o'clock the next day; for extraordinary forecasts, minutes can also be indicated, for example 24134022 - on the 24th from 13-40 to 22 o'clock).

The weather forecast for an aerodrome includes the following elements (in order):

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

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

b weather phenomena;

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

b air temperature (indicated only in some cases);

b presence of turbulence and icing.

Note:

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

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Dangerous weather phenomena for aviation.

Visibility-impairing phenomena

Fog ()- this is an accumulation of water droplets or crystals suspended in the air near the earth's surface, impairing horizontal visibility of less than 1000 m. At a visibility range of 1000 m to 10,000 m, this phenomenon is called haze (=).

One of the conditions for the formation of fog in the ground layer is an increase in moisture content and a decrease in the temperature of moist air to the condensation temperature, the dew point.

Depending on what conditions influenced the formation process, several types of fogs are distinguished.

Intramass fogs

Radiation mists are formed on clear, quiet nights due to radiative cooling of the underlying surface and cooling of the air layers adjacent to it. The thickness of such fogs ranges from several meters to several hundred meters. Their density is greater near the ground, which means visibility is worse here, because... The lowest temperature is observed near the ground. With height their density decreases and visibility improves. Such fogs form throughout the year in the ridges high pressure, in the center of the anticyclone, in the saddles:

They appear first in lowlands, ravines, and floodplains. As the sun rises and the wind increases, radiation fogs dissipate and sometimes turn into a thin layer of low clouds. Radiation fogs are especially dangerous for aircraft landing.

Advective fogs are formed by the movement of a warm, moist, airy mass over the cold underlying surface of a continent or sea. They can be observed in wind speeds of 5 – 10 m/sec. and more, occur at any time of the day, occupy large areas and persist for several days, creating serious interference for aviation. Their density increases with height and the sky is usually not visible. At temperatures from 0 to -10С, icing is observed in such fogs.

More often, these fogs are observed in the cold half of the year in the warm sector of the cyclone and on the western periphery of the anticyclone.

In summer, advective fogs arise over the cold surface of the sea when air moves from warm land.

Advection-radiation fogs are formed under the influence of two factors: the movement of warm air over the cold earth's surface and radiation cooling, which is most effective at night. These fogs can also occupy large areas, but are shorter in duration than advective fogs. They are formed under the same synoptic situation as advective fogs (warm sector of the cyclone, western periphery of the anticyclone), most characteristic of the autumn-winter period.

Mists of the slopes occur when moist air rises calmly along mountain slopes. In this case, the air expands adiabatically and cools.

Mists of evaporation arise due to the evaporation of water vapor from a warm water surface into a colder surrounding

air. This is how a fog of evaporation appears over the Baltic and Black Seas, on the Angara River and in other places when the water temperature is 8-10°C or more higher than the air temperature.

Frosty (furnace) mists are formed in winter at low temperatures in areas of Siberia and the Arctic, usually over small settlements(airfields) in the presence of surface inversion.

They usually form in the morning, when the air begins to receive large number condensation nuclei along with smoke from the firebox and stoves. They quickly acquire significant density. During the day, as the air temperature rises, they collapse and weaken, but intensify again in the evening. Sometimes such fogs last for several days.

Frontal fogsare formed in the zone of slowly moving and stationary fronts (warm and warm occlusion fronts) at any (more often in cold) time of day and year.

Prefrontal fogs are formed due to the saturation of cold air located under the frontal surface with moisture. Conditions for the formation of prefrontal fog are created when the temperature of the falling rain is higher than the temperature of cold air located near the surface of the earth.

The fog that forms during the passage of a front is a cloud system that has spread to the surface of the earth* This is especially common when the front passes over higher elevations.

The conditions of formation of behind-frontal fog are practically no different from the conditions of formation of advective fogs.

Blizzard - transfer of snow by strong winds over the surface of the earth. The intensity of a snowstorm depends on wind speed, turbulence and snow conditions. A snowstorm can impair visibility, make landing difficult, and sometimes prevent aircraft from taking off and landing. During severe, prolonged snowstorms, the performance of airfields deteriorates.

There are three types of snowstorms: drifting snow, blowing snow and general snowstorm.

Drifting snow() - snow transport by wind only at the surface of the snow cover up to a height of 1.5 m. Observed in the rear of the cyclone and the front part of the anticyclone with a wind of 6 m/sec. and more. It causes swelling on the runway and makes it difficult to visually determine the distance to the ground. The horizontal visibility of drifting snow does not impair.

Blizzard() - the transfer of snow by the wind along the earth's surface with a rise to a height of more than two meters. Observed with winds of 10-12 m/sec or more. The synoptic situation is the same as with drifting snow (the rear of the cyclone, the eastern periphery of the anticyclone). Visibility during a blowing snow it depends on the wind speed. If the wind is II-I4 m/sec., then the horizontal visibility can be from 4 to 2 km, with a wind of 15-18 m/sec. 2 km up to 500 m and with a wind of more than 18 m/sec. - less than 500 m.

General snowstorm () - snow falling from the clouds and simultaneously being transported by the wind along the earth's surface. It usually starts when there is wind 7 m/sec. and more. Occurs on atmospheric fronts. The height extends to the bottom of the clouds. In strong winds and heavy snowfall, visibility sharply worsens both horizontally and vertically. Often during takeoff and landing in a general snowstorm, the aircraft becomes electrified, distorting instrument readings

Dust storm() - transfer of large quantities of dust or sand by strong winds. It is observed in deserts and places with arid climates, but sometimes occurs in temperate latitudes. The horizontal extent of a dust storm can be. from a few hundred meters to 1000 km. The vertical height of the atmospheric dust layer varies from 1-2 km (dusty or sandy drifting snow) to 6-9 km (dust storms).

The main reasons for the formation of dust storms are the turbulent wind structure that occurs during daytime heating of the lower layers of air, squally wind patterns, and sudden changes in the pressure gradient.

The duration of a dust storm ranges from a few seconds to several days. Frontal dust storms present especially great difficulties in flight. As the front passes, dust rises to great heights and is transported over considerable distances.

Haze() - cloudiness of the air caused by particles of dust and smoke suspended in it. In severe haze, visibility can be reduced to hundreds and tens of meters. More often, visibility in darkness is more than 1 km. Observed in steppes and deserts: maybe after dust storms, forest and peat fires. Haze over large cities is associated with air pollution from smoke and dust of local origin. i

Aircraft icing.

The formation of ice on the surface of an aircraft when flying in supercooled clouds or fog is called icing.

Severe and moderate icing, in accordance with the Civil Aviation Regulations, are classified as dangerous meteorological phenomena for flights.

Even with light icing, the aerodynamic qualities of the aircraft change significantly, the weight increases, engine power decreases, and the operation of control mechanisms and some navigation instruments is disrupted. Ice released from icy surfaces can get into the engines or onto the casing, leading to mechanical damage. Icing on the cockpit windows impairs visibility and reduces visibility.

The complex impact of icing on an aircraft poses a threat to flight safety, and in some cases can lead to an accident. Icing is especially dangerous during takeoff and landing as a concomitant phenomenon in the event of failures of individual aircraft systems.

The process of aircraft icing depends on many meteorological and aerodynamic variable factors. The main cause of icing is the freezing of supercooled water droplets when they collide with an aircraft. The manual for meteorological support of flights provides for a conditional gradation of icing intensity.

The intensity of icing is usually measured by the thickness of ice growth per unit time. Thickness is usually measured in millimeters of ice deposited on different parts of the aircraft per minute (mm/min). When measuring ice deposits on the leading edge of a wing, it is customary to consider:

Weak icing - up to 0.5 mm/min;

Moderate - from 0.5 to 1.0 mm/min.;

Strong - more than 1.0 mm/min.

With a weak degree of icing, periodic use of anti-icing agents completely frees the aircraft from ice, but if the systems fail, flying in icing conditions is more than dangerous. A moderate degree is characterized by the fact that even a short-term entry of an aircraft into an icing zone without the anti-icing systems turned on is dangerous. If the degree of icing is severe, systems and means cannot cope with the growing ice and an immediate exit from the icing zone is necessary.

Aircraft icing occurs in clouds located from the ground to the height 2-3 km. At negative temperatures ah, icing is most likely in water clouds. In mixed clouds, icing depends on the water content of their droplet-liquid part; in crystalline clouds, the probability of icing is low. Icing is almost always observed in intramass stratus and stratocumulus clouds at temperatures from 0 to -10°C.

In frontal clouds, the most intense icing of aircraft occurs in cumulonimbus clouds associated with cold fronts, occlusion fronts and warm fronts.

In nimbostratus and altostratus clouds of a warm front, intense icing occurs if there is little or no precipitation, and with heavy precipitation on the warm front, the probability of icing is low.

The most intense icing can occur when flying under clouds in an area of ​​freezing rain and/or drizzle.

Icing is unlikely in upper-level clouds, but it should be remembered that intense icing is possible in cirrostratus and cirrocumulus clouds if they remain after the destruction of thunderstorm clouds.

Icing could occur at temperatures from -(-5 to -50°C in clouds, fog and precipitation. As statistics show, the largest number of cases of icing. Sun is observed at air temperatures from 0 to -20°C, and especially from 0 to - 10°C. Icing of gas turbine engines can also occur at positive temperatures from 0 to +5°C.

Relationship between icing and precipitation

Supercooled rain is very dangerous due to icing ( N.S.) The radius of raindrops is several mm, so even light freezing rain can very quickly lead to severe icing.

Drizzle (St ) at negative temperatures during a long flight also leads to severe icing.

Sleet (NS) , WITH B ) - usually falls out in flakes and is very dangerous due to strong icing.

Icing in “dry snow” or crystalline clouds is unlikely. However, icing of jet engines is possible even in such conditions - the surface of the air intake can cool to 0°, snow, sliding along the walls of the air intake into the engine, can cause a sudden cessation of combustion in the jet engine.

Types and forms of aircraft icing.

The following parameters determine the type and shape of aircraft icing:

Microphysical structure of clouds (whether they consist only of supercooled drops, only of crystals, or have a mixed structure, spectral size of drops, water content of the cloud, etc.);

- temperature of the air flow;

- speed and flight mode;

- shape and size of parts;

As a result of the influence of all these factors, the types and forms of ice deposits on the surface of aircraft are extremely diverse.

The type of ice deposits is divided into:

Transparent or glassy, ​​it is most often formed when flying in clouds containing mainly large drops, or in an area of ​​supercooled rain at air temperatures from 0 to -10 ° C and below.

Large drops, hitting the surface of the aircraft, spread and gradually freeze, first forming a smooth, ice film that almost does not distort the profile of the bearing surfaces. With significant growth, the ice becomes lumpy, which makes this type of deposit, which has the highest density, very dangerous due to the increase in weight and significant changes in the aerodynamic characteristics of the aircraft;

Matt or mixed appears in mixed clouds at temperatures from -6 to -12 ° C. Large drops spread before freezing, small ones freeze without spreading, and snowflakes and crystals freeze into a film of supercooled water. As a result, translucent or opaque ice with uneven a rough surface, the density of which is slightly less than transparent. This type of deposit greatly distorts the shape of parts of the aircraft flown by the air flow, adheres firmly to its surface and reaches a large mass, therefore it is the most dangerous;

White or coarse, in fine-droplet clouds of layered form and fog, it is formed at temperatures below - 10 Drops quickly freeze when they hit the surface, retaining their shape. This type of ice is characterized by porosity and low specific gravity. Coarse ice has weak adhesion to aircraft surfaces and is easily separated during vibrations, but during a long flight in an icing zone, the accumulating ice, under the influence of mechanical air shocks, becomes compacted and acts as matte ice;

Drizzle is formed when there are small supercooled droplets in the clouds with a large number of ice crystals at a temperature of -10 to -15°C. Frost deposits, uneven and rough, adhere weakly to the surface and are easily dislodged by air flow when vibrating. Dangerous during a long flight in an icing zone, reaching great thickness and having an uneven shape with torn protruding edges in the form of pyramids and columns;

frost occurs as a result of sublimation of water vapor when BC suddenly enters from cold layers to warm ones. It is a light fine-crystalline coating that disappears when the sun temperature equalizes the air temperature. Frost: not dangerous, but can be a stimulator of severe icing when the aircraft enters the clouds.

The shape of ice deposits depends on the same reasons as the types:

- profile, having the appearance of the profile on which the ice was deposited; most often made of transparent ice;

- wedge-shaped is a clip on the front wing made of white coarse ice;

The groove-shaped has a reverse V appearance at the leading edge of the streamlined profile. The recess is obtained due to kinetic heating and thawing of the central part. These are lumpy, rough growths of matte ice. This is the most dangerous type of icing

- barrier or mushroom-shaped - a roller or separate streaks behind the heating zone of transparent and matte ice;

The shape largely depends on the profile, which varies along the entire length of the wing or propeller blade, so various shapes icing.

Effect of high speeds on icing.

The influence of air speed on the intensity of icing affects in two ways:

An increase in speed leads to an increase in the number of droplets colliding with the surface of the aircraft"; and thus the intensity of icing increases;

As speed increases, the temperature of the frontal parts of the aircraft increases. Kinetic heating appears, which affects the thermal conditions of the icing process and begins to manifest itself noticeably at speeds of more than 400 km/h

V km/h 400 500 600 700 800 900 1100

T C 4 7 10 13 17 21 22

Calculations show that kinetic heating in clouds is 60^ of kinetic heating in dry air (heat loss due to the evaporation of part of the droplets). In addition, kinetic heating is unevenly distributed over the surface of the aircraft and this leads to the formation of a dangerous form of icing.

Type of ground icing.

Deposition may occur on the surface of aircraft on the ground at sub-zero temperatures. various types ice. According to the conditions of formation, all types of ice are divided into three main groups.

The first group includes frost, hoarfrost and solid deposits formed as a result of the direct transition of water vapor into ice (sublimation).

Frost mainly covers the upper horizontal surfaces of the aircraft when they are cooled to subzero temperatures on clear, quiet nights.

Frost forms in moist air, mainly on the protruding windward parts of the aircraft, in frosty weather, fog and light winds.

Frost and frost adhere weakly to the surface of the aircraft and are easily removed by mechanical treatment or hot water.

The second group includes types of ice formed when supercooled drops of rain or drizzle freeze. In the case of slight frosts (from 0 to -5°C), falling raindrops spread over the surface of the aircraft and freeze in the form of transparent ice.

At lower temperatures, the drops quickly freeze and frosted ice forms. These types of ice can reach large sizes and adhere firmly to the surface of the aircraft.

The third group includes types of ice deposited on the surface of an aircraft when falling rain, sleet, or fog drops freeze. These types of ice do not differ in structure from the types of ice of the second group.

Such types of aircraft icing on the ground sharply worsen its aerodynamic characteristics and increase its weight.

From the above it follows that before takeoff the aircraft must be thoroughly cleared of ice. You need to check the condition of the aircraft surface especially carefully at night at subzero air temperatures. It is prohibited to take off on an airplane whose surface is covered with ice.

Features of helicopter icing.

Physico-meteorological conditions for helicopter icing are similar to those for airplanes.

At temperatures from 0 to ~10°C, ice is deposited on the propeller blades mainly at the axis of rotation and spreads to the middle. The ends of the blades are not covered with ice due to kinetic heating and high centrifugal force. At constant number rpm, the intensity of propeller icing depends on the water content of the cloud or supercooled rain, the size of the droplets and the air temperature. At air temperatures below -10°C, the propeller blades become completely icy, and the intensity of ice growth at the leading edge is proportional to the radius. When the main rotor becomes icy, strong vibration occurs, affecting the controllability of the helicopter, the engine speed drops, and the speed cannot be increased to the previous value. restores the lifting force of the propeller, which can lead to loss of its instability.

Ice.

This layer of dense ice (opaque or transparent). growing on the surface of the earth and on objects when supercooled rain or drizzle falls. Usually observed at temperatures from 0 to -5°C, less often at lower temperatures: (up to -16°). Ice forms in the zone of a warm front, most often in the zone of the occlusion front, stationary front and in the warm sector of the cyclone.

Black ice – ice on the earth's surface that forms after a thaw or rain as a result of the onset of cold weather, as well as ice remaining on the earth after the cessation of precipitation (after ice).

Flight operations in icing conditions.

Flights in icing conditions are permitted only on approved aircraft. In order to avoid the negative consequences of icing, during the pre-flight preparation period it is necessary to carefully analyze the meteorological situation along the route and, based on data on actual weather and the forecast, determine the most favorable flight levels.

Before entering cloudy areas where icing is likely, anti-icing systems should be turned on, since delay in turning on significantly reduces their effectiveness.

If icing is severe, anti-icing agents are not effective, so the flight level should be changed in consultation with the traffic service.

IN winter period, when the cloud layer with an isotherm from -10 to -12°C is located close to the earth's surface, it is advisable to go up to the temperature region below -20°C, leaving the rest of the year, if the height allowance allows, down to the region of positive temperatures.

If the icing does not disappear when changing flight levels, you must return to the departure point or land at the earliest alternate airfield.

Difficult situations most often arise due to pilots underestimating the danger of even mild icing.

THUNDERSTORMS

Thunderstorm is complex atmospheric phenomenon, in which multiple electrical discharges are observed, accompanied by a sound phenomenon - thunder, as well as rainfall precipitation.

Conditions necessary for the development of intramass thunderstorms:

instability of the air mass (large vertical temperature gradients, at least up to an altitude of about 2 km - 1/100 m before the condensation level and - > 0.5°/100 m above the condensation level);

High absolute air humidity (13-15 mb. in the morning);

High temperatures at the surface of the earth. The zero isotherm on days with thunderstorms lies at an altitude of 3-4 km.

Frontal and orographic thunderstorms develop mainly due to the forced rise of air. Therefore, these thunderstorms in the mountains begin earlier and end later, form on the windward side (if these are high mountain systems) and are stronger than in flat areas for the same synoptic position.

Stages of development of a thundercloud.

The first is the growth stage, which is characterized by a rapid rise to the top and maintenance appearance droplet cloud. During thermal convection during this period, cumulus clouds (Ci) turn into powerful cumulus clouds (Ci conq/). In clouds b, only upward air movements from several m/s (Ci) to 10-15 m/s (Ci conq/) are observed under the clouds. Then the upper layer of clouds moves into the zone of negative temperatures and acquires a crystalline structure. These are already cumulonimbus clouds and heavy rain begins to fall from them, downward movements above 0° appear - severe icing.

Second - stationary stage , characterized by the cessation of intensive upward growth of the cloud top and the formation of an anvil (cirrus clouds, often elongated in the direction of movement of the thunderstorm). These are cumulonimbus clouds in a state of maximum development. Turbulence is added to vertical movements. The speed of ascending flows can reach 63 m/s, and descending flows ~ 24 m/s. In addition to showers, there may be hail. At this time, electrical discharges - lightning - are formed. There may be squalls and tornadoes under the cloud. The upper limit of the clouds reaches 10-12 km. In the tropics, individual thunderstorm cloud tops develop to a height of 20-21 km.

The third is the stage of destruction (dissipation), during which the droplet-liquid part of the cumulonimbus cloud is washed away, and the top, which has turned into a cirrus cloud, often continues to exist independently. At this time, electrical discharges stop, precipitation weakens, and downward air movements predominate.

During the transition seasons and during the winter development stage, all processes of a thundercloud are much less pronounced and do not always have clear visual signs

According to the Civil Aviation Administration, a thunderstorm over an airfield is considered if the distance to the thunderstorm is No. km. and less. A thunderstorm is distant if the distance to the thunderstorm is more than 3 km.

For example: “09.55 distant thunderstorm in the northeast, moving to the southwest.”

“18.20 thunderstorm over the airfield.”

Phenomena associated with a thundercloud.

Lightning.

The period of electrical activity of a thundercloud is 30-40 minutes. The electrical structure of St. is very complex and changes rapidly in time and space. Most observations of thunderclouds show that a positive charge is usually formed in the upper part of the cloud, a negative charge in the middle part, and both positive and negative charges in the lower part. The radius of these areas with opposite charges varies from 0.5 km to 1-2 km.

The breakdown strength of the electric field for dry air is I million V/m. In clouds, for lightning discharges to occur, it is enough for the field strength to reach 300-350 thousand V/m. (measured values ​​during experimental flights) Apparently, these or close to them field strength values ​​represent the strength of the beginning of the discharge, and for its propagation, strengths that are much lower, but covering a large space, are sufficient. The frequency of discharges in a moderate thunderstorm is about 1/min, and in an intense thunderstorm – 5–10/min.

Lightning- this is a visible electrical discharge in the form of curved lines, lasting a total of 0.5 - 0.6 seconds. The development of a discharge from a cloud begins with the formation of a stepped leader (streamer), which advances in “Jumps” with a length of 10-200 m. Along the ionized lightning channel, a return stroke develops from the surface of the earth, which transfers the main lightning charge. The current strength reaches 200 thousand A. Usually following the first step leader after hundredths of a second. development occurs along the same channel of the arrow-shaped leader, after which the second return blow occurs. This process can be repeated many times.

Linear lightning are formed most often, their length is usually 2-3 km (between clouds up to 25 km), the average diameter is about 16 cm (maximum up to 40 cm), the path is zigzag.

Flat zipper- a discharge covering a significant part of the cloud and states of luminous quiet discharges emitted by individual droplets. Duration about 1 sec. You cannot mix flat lightning with lightning. Lightning strikes are discharges of distant thunderstorms: lightning is not visible and thunder is not heard, only the lighting of the clouds by lightning differs.

Ball lightning brightly glowing ball of white or reddish

colors with an orange tint and an average diameter of 10-20 cm. Appears after a linear lightning discharge; moves in the air slowly and silently, can penetrate inside buildings and aircraft during flight. Often, without causing harm, it goes away unnoticed, but sometimes it explodes with a deafening crash. The phenomenon can last from a few seconds to several minutes. This is a little studied physicochemical process.

A lightning discharge into an aircraft can lead to depressurization of the cabin, fire, blinding of the crew, destruction of the skin, individual parts and radio equipment, magnetization of steel

cores in devices,

Thunder caused by heating and therefore expansion of air along the lightning path. In addition, during the discharge, water molecules decompose into their component parts with the formation of “explosive gas” - “channel explosions”. Since the sound from different points of the lightning path does not arrive simultaneously and is reflected many times from clouds and the surface of the earth, thunder has the character of long peals. Thunder is usually heard at a distance of 15-20 km.

hail- This is precipitation falling from the Earth in the form of spherical ice. If above the 0° level the maximum increase in upward flows exceeds Yum/sec, and the top of the cloud is located in the temperature zone - 20-25°, then ice formation is possible in such a cloud. A hailstone is formed above the level maximum speed upward flows, and here the accumulation of large drops and the main growth of hailstones occurs. In the upper part of the cloud, when crystals collide with supercooled drops, snow grains (embryos of hailstones) are formed, which, falling down, turn into hail in the zone of accumulation of large drops. The time interval between the beginning of the formation of hailstones in the cloud and their falling out of the cloud is about 15 minutes. The width of the “hail road” can be from 2 to 6 km, length 40-100 km. The thickness of the layer of fallen hail sometimes exceeds 20 cm. The average duration of hail is 5 10 minutes, but in some cases it may be longer. Most often, hailstones with a diameter of 1-3 cm are found, but they can be up to 10 cm or more. .Hail is detected not only under a cloud, but can damage aircraft at high altitudes (up to an altitude of 13,700 m and up to 15-20 km from a thunderstorm).

Hail can break the glass of the pilot's cockpit, destroy the radar fairing, pierce or make dents in the casing, and damage the leading edge of the wings, stabilizer, and antennas.

Heavy rain shower sharply reduces visibility to less than 1000 m, can cause engines to shut down, degrades the aerodynamic qualities of the aircraft and can, in some cases, without any wind shear, reduce the lifting force during approach or takeoff by 30%.

Squall- a sharp increase (more than 15 m/s) of wind for several minutes, accompanied by a change in its direction. Wind speed during a squall often exceeds 20 m/s, reaching 30 and sometimes 40 m/s or more. The squall zone extends up to 10 km around the thundercloud, and if these are very powerful thunderstorms, then in the front part the width of the squall zone can reach 30 km. Swirls of dust near the surface of the earth in the region of a cumulonimbus cloud are visual sign“front of air gusts” (squalls) Squalls are associated with intramass and frontal strongly developed NE clouds.

Squall Gate- a vortex with a horizontal axis in the front part of a thundercloud. This is a dark, hanging, rotating cloud bank 1-2 km before a continuous curtain of rain. Usually the vortex moves at an altitude of 500m, sometimes it drops to 50m. After its passage, a squall is formed; there may be a significant decrease in air temperature and an increase in pressure caused by the spread of air cooled by precipitation.

Tornado- a vertical vortex descending from a thundercloud to the ground. The tornado looks like a dark cloud column with a diameter of several tens of meters. It descends in the form of a funnel, towards which another funnel of spray and dust can rise from the earth's surface, connecting with the first. Wind speeds in a tornado reach 50 - 100 m/sec with a strong upward component. The pressure drop inside a tornado can be 40-100 mb. Tornadoes can cause catastrophic destruction, sometimes resulting in loss of life. The tornado should be bypassed at a distance of at least 30 km.

Turbulence near thunderclouds has a number of features. It becomes increased already at a distance equal to the diameter of the thundercloud, and the closer to the cloud, the greater the intensity. As the cumulonimbus cloud develops, the turbulence zone increases, with the greatest intensity observed in the rear part. Even after a cloud has completely collapsed, the area of ​​the atmosphere where it was located remains more disturbed, that is, turbulent zones live longer than the clouds with which they are associated.

Above the upper boundary of a growing cumulonimbus cloud, upward movements at a speed of 7-10 m/sec create a layer of intense turbulence 500 m thick. And above the anvil, downward air movements are observed at a speed of 5-7 m/sec, they lead to the formation of a layer with intense turbulence 200 m thick.

Types of thunderstorms.

Intramass thunderstorms formed over the continent. in summer and in the afternoon (over the sea these phenomena are observed most often in winter and at night). Intramass thunderstorms are divided into:

- convective (thermal or local) thunderstorms, which are formed in low-gradient fields (in saddles, in old filling cyclones);

- advective- thunderstorms that form in the rear of the cyclone, because here there is an invasion (advection) of cold air, which in the lower half of the troposphere is very unstable and thermal and dynamic turbulence develops well in it;

- orographic- are formed in mountainous areas, develop more often on the windward side and are stronger and longer lasting (start earlier, end later) than in flat areas under the same weather conditions on the windward side.

Frontal thunderstorms are formed at any time of the day (depending on which front is located in a given area). In summer, almost all fronts (except stationary ones) produce thunderstorms.

Thunderstorm centers in the frontal zone sometimes have zones up to 400-500 km long. On major slow-moving fronts, thunderstorms may be masked by upper- and mid-level clouds (especially on warm fronts). Very strong and dangerous thunderstorms form on the fronts of young deepening cyclones, at the top of the wave, at the point of occlusion. In the mountains, frontal thunderstorms, like frontal thunderstorms, intensify on the windward side. Fronts on the periphery of cyclones, old eroding occlusion fronts, and surface fronts give rise to thunderstorms in the form of separate centers along the front, which during aircraft flights are bypassed in the same way as intramass ones.

In winter, thunderstorms in temperate latitudes rarely form, only in the zone of main, active atmospheric fronts that separate air masses with a large temperature contrast and move at high speed.

Thunderstorms are observed visually and instrumentally. Visual observations have a number of disadvantages. A weather observer, whose observation radius is limited to 10-15 km, records the presence of a thunderstorm. At night, in difficult meteorological conditions, it is difficult to determine cloud shapes.

For instrumental observations of thunderstorms, weather radars (MRL-1, MRL-2. MRL-5), thunderstorm azimuth direction finders (GAT), panoramic thunderstorm recorders (PRG) and lightning markers included in the KRAMS complex (comprehensive radio-technical automatic weather station) are used. .

MRL give the most full information about the development of thunderstorm activity within a radius of up to 300 km.

Based on reflectivity data, it determines the location of the thunderstorm source, its horizontal and vertical dimensions, speed and direction of displacement. Based on observational data, radar maps are compiled.

If thunderstorm activity is observed or predicted in the flight area, during the pre-flight preparation period the flight control center is obliged to carefully analyze the meteorological situation. Using MRL maps, determine the location and direction of movement of thunderstorm (shower) centers, their upper limit, outline detour routes, safe echelon. It is necessary to know the symbols of thunderstorm weather phenomena and heavy rainfall.

When approaching a zone of lightning activity, the pilot-in-command using the radar must assess in advance the possibility of flying through this zone and inform the controller about the flight conditions. For safety, a decision is made to bypass thunderstorms or fly to an alternate airfield.

The dispatcher, using information from the meteorological service and weather reports from the aircraft, is obliged to inform crews about the nature of thunderstorms, their vertical power, directions and speed of displacement and give recommendations on leaving the area of ​​thunderstorm activity.

If powerful cumulus and cumulonimbus clouds are detected in flight by the BRL, it is allowed to bypass these clouds at a distance of at least 15 km from the nearest border of illumination.

The intersection of frontal clouds with individual thunderstorm centers can occur in the place where the distance between

the boundaries of flare on the BRL screen are at least 50 km.

Flight over the upper boundary of powerful cumulus and cumulonimbus clouds is permitted with an elevation of at least 500 m above them.

Aircraft crews are prohibited from intentionally entering powerful cumulus and cumulonimbus clouds and areas of heavy rainfall.

When taking off, landing and the presence of thick cumulus, cumulonimbus clouds in the airfield area, the crew: is obliged to inspect the airfield area with the help of radar, assess the possibility of takeoff, landing and determine the procedure for avoiding thick cumulus, cumulonimbus clouds and areas of heavy rainfall precipitation.

Flight under cumulonimbus clouds is permitted only during the day, outside the zone of heavy rainfall, if:

- aircraft flight altitude above the terrain is at least 200 m and in mountainous areas at least 600 m;

- vertical distance from the aircraft to the bottom of the clouds is at least 200 m.

Electrification of aircraft and discharge of static electricity.

The phenomenon of aircraft electrification is that when flying in clouds, precipitation due to friction (water drops, snowflakes), the surface of the aircraft receives an electric charge, the magnitude of which is greater, the larger the aircraft and its speed, as well as the greater the number of moisture particles contained in unit volume of air. Charges on an aircraft can also appear when flying near clouds that have electric charges. The highest charge density is observed on the sharp convex parts of the aircraft, and an outflow of electricity is observed in the form of sparks, luminous crowns, and a crown.

Most often, aircraft electrification is observed when flying in crystalline clouds of the upper tier, as well as mixed clouds of the middle and lower tiers. Charges can also appear on the aircraft when flying near clouds that have electrical charges.

In some cases, the electric charge that an aircraft has is one of the main causes of aircraft being damaged by lightning in nimbostratus clouds at altitudes of 1500 to 3000 m. The thicker the clouds, the greater the likelihood of damage.

For electrical discharges to occur, it is necessary that a non-uniform electric field exist in the cloud, which is largely determined by the phase state of the cloud.

If the electric field strength between volumetric electric charges in the cloud is less than a critical value, then no discharge occurs between them.

When flying near an airplane cloud that has its own electrical charge, the voltage fields can reach a critical value, then an electrical discharge occurs into the aircraft.

As a rule, lightning does not occur in nimbostratus clouds, although they contain opposite volumetric electric charges. The electric field strength is not sufficient to cause lightning. But if there is an aircraft with a large surface charge near such a cloud or in it, then it can cause a discharge on itself. Lightning originating in a cloud will hit the sun.

A method for predicting dangerous damage to aircraft by electrostatic discharges outside zones of active thunderstorm activity has not yet been developed.

To ensure flight safety in nimbostratus clouds, if the aircraft becomes highly electrified, the flight altitude should be changed in agreement with the dispatcher.

Damage to aircraft by atmospheric electrical discharge more often occurs in cloud systems of cold and secondary cold fronts, in autumn and winter more often than in spring and summer.

Signs of strong electrification of aircraft are:

Noises and crackling in headphones;

Random oscillation of radio compass needles;

Sparking on the glass of the cockpit and the glow of the tips of the wings at night.

Atmospheric turbulence.

The turbulent state of the atmosphere is a state in which disordered vortex movements of various scales and different speeds are observed.

When crossing vortices, the aircraft is exposed to their vertical and horizontal components, which are separate gusts, as a result of which the balance of aerodynamic forces acting on the aircraft is disrupted. Additional accelerations occur, causing the aircraft to sway.

The main causes of air turbulence are contrasts in temperatures and wind speeds that arise for some reason.

When assessing the meteorological situation, it should be taken into account that turbulence can occur under the following conditions:

During takeoff and landing in the lower surface layer due to non-uniform heating of the earth's surface, friction of the flow against the earth's surface (thermal turbulence).

Such turbulence occurs during the warm period of the year and depends on the height of the sun, and the nature of the underlying surface, humidity and the nature of the stability of the atmosphere.

On a sunny summer day, dry ones heat up the most. sandy soils, less - land areas covered with grass, forests, and even less - water surfaces. Unevenly heated areas of land cause uneven heating of the layers of air adjacent to the ground, and ascending movements of unequal intensity.

If the air is dry and stable, and the underlying surface is poor in moisture, then clouds do not form and in such areas there may be weak or moderate turbulence. It spreads from the ground to an altitude of 2500m. Maximum turbulence occurs in the afternoon hours.

If the air is humid, then with: rising currents, clouds of cumulus shapes form (especially with unstable air mass). In this case, the upper boundary of the turbulence is the cloud's top.

When inversion layers intersect in the tropopause zone and the inversion zone above the earth's surface.

At the boundary of such layers, in which the winds often have different directions and speeds, wave-like movements arise, ..^ causing weak or moderate chatter.

Turbulence of the same nature also occurs in the zone of frontal sections, where large contrasts in temperature and wind speed are observed:

- when flying in a jet stream zone due to differences in speed gradients;

When flying over mountainous terrain, orographic bumps form on the leeward side of mountains and hills. . . On the windward side there is a uniform upward flow, and the higher the mountains and the less steep the slopes, the farther from the mountains the air begins to rise. With a ridge height of 1000 m, upward movements begin at a distance of 15 km from it, with a ridge height of 2500-3000 m at a distance of 60-80 km. If the windward slope is heated by the sun, the speed of the rising currents increases due to the mountain-valley effect. But when the slopes are steep and the wind is strong, turbulence will also form inside the updraft, and the flight will occur in a turbulent zone.

Directly above the very top of the ridge, the wind speed usually reaches its greatest value, especially in the layer 300-500m above the ridge, and there can be strong wind.

On the leeward side of the ridge, the plane, falling into a powerful downdraft, will spontaneously lose altitude.

The influence of mountain ranges on air currents under appropriate meteorological conditions extends to high altitudes.

When an air flow crosses a mountain range, leeward waves are formed. They are formed when:

- if the air flow is perpendicular to the mountain range and the speed of this flow at the top is 50 km/h. and more;

- if wind speed increases with height:

If the transshipment air is rich in moisture, then lentil-shaped clouds form in the part where rising air currents are observed.

In the case when dry air passes over a mountain range, cloudless leeward waves are formed and the pilot can completely unexpectedly encounter strong bumps (one of the cases of TIAN).

In zones of convergence and divergence of air flows with a sharp change in flow direction.

In the absence of clouds, this will be the conditions for the formation of CN (clear sky turbulence).

The horizontal length of a nuclear power plant can be several hundred km. A

several hundred meters thick. hundred meters. Moreover, there is such a dependence: the more intense the turbulence (and the associated turbulence of the aircraft), the thinner the layer thickness.

When preparing for a flight, using the configuration of isohypses on the AT-400 and AT-300 maps, you can determine areas of possible aircraft roughness.

Wind shear.

Wind shear is a change in the direction and (or) speed of wind in space, including upward and downward air flows.

Depending on the orientation of points in space and the direction of movement of the aircraft relative to H1Sh, vertical and horizontal wind shears are distinguished.

The essence of the influence of wind shear is that with an increase in the mass of the aircraft (50-200t), the aircraft began to have greater inertia, which prevents a rapid change in ground speed, while its indicated speed changes according to the speed of the air flow.

The greatest danger is posed by wind shear when the aircraft is in landing configuration on the glide path.

Wind shear intensity criteria (recommended by the working group

(ICAO).

Wind shear intensity is a qualitative term	Vertical wind shear – upward and downward flows at 30 m height, horizontal wind shear at 600 m, m/sec.	Effect on aircraft control
Weak	0 - 2	Minor
Moderate	2 – 4	Significant
Strong	4 – 6	Dangerous
Very strong	More than 6	Dangerous

Many AMSGs do not have continuous wind data (for any 30-meter layer) in the surface layer, so the wind shear values ​​are recalculated to the 100-meter layer:

0-6 m/sec. - weak; 6 -13 m/sec. - moderate; 13 -20 m/sec, strong

20 m/sec. very strong

Horizontal (lateral) wind shears caused by... sharp changes in wind direction with height cause a tendency for the aircraft to shift from the centerline of the upper propeller. When landing an aircraft, this is a challenge ^ there is a danger of the ground touching the runway, during takeoff the layout

increase the lateral displacement beyond the safe climb sector.

Wertsch
Vertical wind shear in prizog

When the wind increases sharply with altitude, positive wind shear occurs.