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1 kilometer per hour [km/h] = 0.277777777777778 meter per second [m/s]

Initial value

Converted value

meter per second meter per hour meter per minute kilometer per hour kilometer per minute kilometers per second centimeter per hour centimeter per minute centimeter per second millimeter per hour millimeter per minute millimeter per second foot per hour foot per minute foot per second yard per hour yard per minute yard per second mile per hour mile per minute mile per second knot knot (Brit.) speed of light in vacuum first space velocity second space velocity third space velocity earth's rotation speed sound speed in fresh water sound speed in sea water (20°C, depth 10 meters) Mach number (20°C, 1 atm) Mach number (SI standard)

Bulk charge density

More about speed

General information

Speed ​​is a measure of the distance traveled in a given time. Velocity can be a scalar quantity or a vector value - the direction of motion is taken into account. The speed of movement in a straight line is called linear, and in a circle - angular.

Speed ​​measurement

average speed v find by dividing the total distance traveled ∆ x for the total time ∆ t: v = ∆x/∆t.

In the SI system, speed is measured in meters per second. Also commonly used are kilometers per hour in the metric system and miles per hour in the US and UK. When, in addition to the magnitude, the direction is also indicated, for example, 10 meters per second to the north, then we are talking about vector speed.

The speed of bodies moving with acceleration can be found using the formulas:

• a, with initial speed u during the period ∆ t, has a final speed v = u + a×∆ t.
• body moving with constant acceleration a, with initial speed u and final speed v, has an average speed ∆ v = (u + v)/2.

Average speeds

The speed of light and sound

According to the theory of relativity, the speed of light in a vacuum is the highest speed at which energy and information can travel. It is denoted by the constant c and equal to c= 299,792,458 meters per second. Matter cannot move at the speed of light because it would require an infinite amount of energy, which is impossible.

The speed of sound is usually measured in an elastic medium and is 343.2 meters per second in dry air at 20°C. The speed of sound is lowest in gases and highest in solids. It depends on the density, elasticity, and shear modulus of the substance (which indicates the degree of deformation of the substance under shear loading). Mach number M is the ratio of the speed of a body in a liquid or gas medium to the speed of sound in this medium. It can be calculated using the formula:

M = v/a,

where a is the speed of sound in the medium, and v is the speed of the body. The Mach number is commonly used in determining speeds close to the speed of sound, such as aircraft speeds. This value is not constant; it depends on the state of the medium, which, in turn, depends on pressure and temperature. Supersonic speed - speed exceeding 1 Mach.

Vehicle speed

Below are some vehicle speeds.

• Passenger aircraft with turbofan engines: the cruising speed of passenger aircraft is from 244 to 257 meters per second, which corresponds to 878–926 kilometers per hour or M = 0.83–0.87.
• High-speed trains (like the Shinkansen in Japan): These trains reach top speeds of 36 to 122 meters per second, i.e. 130 to 440 kilometers per hour.

animal speed

The maximum speeds of some animals are approximately equal:

human speed

• Humans walk at about 1.4 meters per second, or 5 kilometers per hour, and run at up to about 8.3 meters per second, or 30 kilometers per hour.

Examples of different speeds

four dimensional speed

In classical mechanics, the vector velocity is measured in three-dimensional space. According to the special theory of relativity, space is four-dimensional, and the fourth dimension, space-time, is also taken into account in the measurement of speed. This speed is called four-dimensional speed. Its direction may change, but the magnitude is constant and equal to c, which is the speed of light. Four-dimensional speed is defined as

U = ∂x/∂τ,

where x represents the world line - a curve in space-time along which the body moves, and τ - "proper time", equal to the interval along the world line.

group speed

Group velocity is the velocity of wave propagation, which describes the propagation velocity of a group of waves and determines the rate of wave energy transfer. It can be calculated as ∂ ω /∂k, where k is the wave number, and ω - angular frequency. K measured in radians / meter, and the scalar frequency of wave oscillations ω - in radians per second.

Hypersonic speed

Hypersonic speed is a speed exceeding 3000 meters per second, that is, many times higher than the speed of sound. Solid bodies moving at such a speed acquire the properties of liquids, because due to inertia, the loads in this state are stronger than the forces that hold the molecules of matter together during a collision with other bodies. At ultra-high hypersonic speeds, two colliding solid bodies turn into gas. In space, bodies move at precisely this speed, and engineers designing spacecraft, orbital stations, and spacesuits must take into account the possibility of a station or astronaut colliding with space debris and other objects when working in outer space. In such a collision, the skin of the spacecraft and the suit suffer. Equipment designers are conducting hypersonic collision experiments in special laboratories to determine how strong impact suits can withstand, as well as skins and other parts of the spacecraft, such as fuel tanks and solar panels testing them for strength. To do this, spacesuits and skin are subjected to impacts by various objects from a special installation with supersonic speeds exceeding 7500 meters per second.

Each a natural phenomenon, which has different degrees of severity, it is customary to evaluate in accordance with certain criteria. Especially if information about it must be transmitted quickly and accurately. For wind strength, the Beaufort scale has become a single international benchmark.

Developed by the British rear admiral, a native of Ireland, Francis Beaufort (emphasis falls on the second syllable) in 1806, the system, improved in 1926 by adding information about the equivalence of wind strength in points of its specific speed, allows you to fully and accurately characterize this atmospheric process, while remaining relevant and to this day.

What is wind?

Wind is the movement of air masses parallel to the surface of the planet (horizontally above it). This mechanism is caused by pressure difference. The direction of movement always comes from the higher area.

To describe the wind, it is customary to use the following characteristics:

• speed (measured in meters per second, kilometers per hour, knots and points);
• wind strength (in points and m.s. - meters per second, the ratio is approximately 1:2);
• direction (according to cardinal directions).

The first two parameters are closely related. They can be mutually denoted by each other's units of measurement.

The direction of the wind is determined by the side of the world from where the movement began (from the north - the north wind, etc.). Velocity determines the pressure gradient.

Baric gradient (otherwise - barometric gradient) - change in atmospheric pressure per unit distance along the normal to a surface of equal pressure (isobaric surface) in the direction of decreasing pressure. In meteorology, the horizontal barometric gradient is usually used, that is, its horizontal component (Great Soviet Encyclopedia).

The speed and strength of the wind cannot be separated. A large difference in indicators between atmospheric pressure zones generates a strong and rapid movement of air masses above the earth's surface.

Features of wind measurement

In order to correctly correlate the data of meteorological services with your real position or to make a measurement correctly, you need to know what standard conditions professionals use.

• The measurement of the strength and speed of the wind takes place at a height of ten meters on an open flat surface.
• The name of the wind direction is given by the cardinal direction from which it blows.

Managers of water transport, as well as lovers of spending time in nature, often purchase anemometers that determine the speed, which is easy to correlate with the wind force in points. There are waterproof models. For convenience, devices of various compactness are produced.

In the Beaufort system, the description of the height of the waves, correlated with a certain force of wind in points, is given for the open sea. It will be much less in shallow water areas and coastal zones.

From personal to global use

Sir Francis Beaufort not only had a high military rank in the navy, but was also a successful practical scientist who held important posts, a hydrographer and cartographer, who brought great benefits to the country and the world. One of the seas in the Arctic Ocean, washing Canada and Alaska, bears his name. An Antarctic island is named after Beaufort.

A convenient system for estimating wind strength in points, available for fairly accurate determination of the severity of the phenomenon "by eye", Francis Beaufort created for his own use in 1805. The scale had a gradation from 0 to 12 points.

In 1838, the system of visual assessment of weather and wind strength in points began to be officially used by the British Navy. In 1874 it was adopted by the international synoptic community.

In the 20th century, several more improvements were made to the Beaufort scale - the ratio of points and a verbal description of the manifestation of the elements with wind speed (1926), and five more divisions were added - points for grading the strength of hurricanes (USA, 1955).

Criteria for estimating wind strength in Beaufort points

V modern form The Beaufort scale has several characteristics that allow, in combination, to most accurately correlate a specific atmospheric phenomenon with its indicators in points.

• First, it is verbal information. Verbal description of the weather.
• Average speed in meters per second, kilometers per hour and knots.
• The impact of moving air masses on characteristic objects on land and sea is determined by typical manifestations.

Non-dangerous wind

Safe wind is determined in the range from 0 to 4 points.

	Name	Wind speed (m/s)	Wind speed (km/h)		Description	Characteristic
	Calm, complete calm (Calm)		less than 1 km/h		Smoke movement - vertically upwards, tree leaves do not move	The surface of the sea is immovable, smooth
	Quiet wind (Light Air)				The smoke has a small angle of inclination, the weather vane is motionless	Light ripples without foam. Waves no higher than 10 centimeters
	Light Breeze				Feel the breath of the wind on the skin of the face, there is a movement and rustle of leaves, a slight movement of the weather vane	Short low waves (up to 30 centimeters) with a glass-like crest
	Weak (Gentle Breeze)				The continuous movement of foliage and thin branches on the trees, the waving of flags	Waves remain short but more noticeable. The ridges begin to tip over and turn into foam. Rare small "lambs" appear. The height of the waves reaches 90 centimeters, but on average does not exceed 60
	Moderate (Moderate Breeze)				Dust, small debris begins to rise from the ground	The waves become longer and rise up to one and a half meters. "Lambs" appear often

A wind of 5 points, characterized as "fresh", or fresh breeze, can be called borderline. Its speed ranges from 8 to 10.7 meters per second (29-38 km/h, or 17 to 21 knots). Thin trees sway along with the trunks. Waves rise up to 2.5 (average up to two) meters. Sometimes there are splashes.

Wind that brings trouble

With a wind force of 6 points, strong phenomena begin that can cause damage to health and property.

Points	Name	Wind speed (m/s)	Wind speed (km/h)	Wind speed (sea streaks)	Description	Characteristic
	Strong (Strong Breeze)				The thick branches of the trees sway strongly, the hum of telegraph wires is heard	Formation of large waves, foam crests acquire significant volume, splashing is likely. The average wave height is about three meters, the maximum reaches four
	Strong (Moderate gale)				The trees are swinging whole	Active movement of waves up to 5.5 meters high overlapping each other, foam dispersion along the wind direction
	Very strong (Gale)				Tree branches break from the pressure of the wind, it is difficult to walk against its direction	Waves of significant length and height: average - about 5.5 meters, maximum - 7.5 m. Moderately high long waves. Sprays fly up. Foam falls in stripes, the vector coincides with the direction of the wind
	Storm (Strong gale)				Wind damages buildings, begins to destroy roof tiles	Waves up to ten meters with an average height of up to seven. The streaks of foam become wider. Tilting combs splatter. Reduced visibility

Dangerous force of the wind

Wind force from ten to twelve points is dangerous and is characterized as a strong (storm) and severe storm (violent storm), as well as a hurricane (hurricane).

Wind uproots trees, damages buildings, destroys vegetation, destroys buildings. The waves make a deafening noise from 9 meters and above, long. At sea, they reach a dangerous height even for large ships - from nine meters and above. Foam covers the water surface, visibility is zero or close to such an indicator.

The speed of movement of air masses is from 24.5 meters per second (89 km / h) and reaches from 118 kilometers per hour with a wind force of 12 points. Violent storms and hurricanes (winds of magnitudes 11 and 12) are very rare.

Additional five points to the classical Beaufort scale

Since hurricanes are also not identical to each other in terms of intensity and degree of damage, in 1955 the United States Weather Bureau adopted an addition to the standard Beaufort classification in the form of five scale units. Wind strength from 13 to 17 points inclusive - these are clarifying characteristics for destructive hurricane winds and related phenomena environment.

How to protect yourself when the elements are raging?

If the storm warning of the Ministry of Emergency Situations catches in an open area, it is better to follow the advice and reduce the risk of accidents.

First of all, you should pay attention to warnings every time - there is no guarantee that the atmospheric front will come to the area where you are, but you also cannot be sure that it will bypass it again. All items should be removed or securely fastened, to protect pets.

If a heavy wind catches in a fragile structure - a garden house or other light structures - it is better to close the windows from the air movement side, and if necessary, strengthen them with shutters or boards. On the leeward, on the contrary, slightly open and fix in this position. This will eliminate the danger of an explosive effect from the pressure difference.

It is important to remember that any strong wind can bring with it unwanted precipitation - in winter it is blizzards and snowstorms, in summer dust and sand storms are possible. It should also be borne in mind that strong winds can occur even in absolutely clear weather.

Wind(horizontal component of air movement relative to the earth's surface) is characterized by direction and speed.
Wind speed measured in meters per second (m/s), kilometers per hour (km/h), knots or Beaufort (wind force). A knot is a nautical measure of speed, 1 nautical mile per hour, approximately 1 knot equals 0.5 m/s. The Beaufort scale (Francis Beaufort, 1774-1875) was created in 1805.

Direction of the wind(where it blows from) is indicated either in rhumbs (on a 16-rhumb scale, for example, north wind - C, northeast - NE, etc.), or in angles (relative to the meridian, north - 360 ° or 0 °, east - 90°, south - 180°, west - 270°), fig. one.

wind name	Speed, m/s	Speed, km/h	Knots	Wind force, points	wind action
Calm	0	0	0	0	The smoke rises vertically, the leaves of the trees are motionless. Mirror-smooth sea
Quiet	1	4	1-2	1	The smoke deviates from the vertical direction, there are light ripples on the sea, there is no foam on the ridges. Wave height up to 0.1 m
Light	2-3	7-10	3-6	2	The wind is felt in the face, the leaves rustle, the weather vane starts to move, the sea has short waves with a maximum height of up to 0.3 m
Weak	4-5	14-18	7-10	3	Leaves and thin branches of trees sway, light flags sway, slight excitement on the water, occasionally small "lambs" form. Average wave height 0.6 m
Moderate	6-7	22-25	11-14	4	The wind raises dust, pieces of paper; thin branches of trees sway, white "lambs" on the sea are visible in many places. Maximum wave height up to 1.5 m
Fresh	8-9	29-32	15-18	5	Branches and thin trunks of trees sway, the wind is felt by hand, white "lambs" are visible on the water. Maximum wave height 2.5 m, average - 2 m
Strong	10-12	36-43	19-24	6	The thick branches of the trees sway, the thin trees bend, the telephone wires hum, the umbrellas are hardly used; white foamy ridges occupy large areas, water dust is formed. Maximum wave height - up to 4 m, average - 3 m
Strong	13-15	47-54	25-30	7	Tree trunks sway, large branches bend, it is difficult to go against the wind, the crests of the waves are torn off by the wind. Maximum wave height up to 5.5 m
Very strong	16-18	58-61	31-36	8	Thin and dry branches of trees break, it is impossible to speak in the wind, it is very difficult to go against the wind. Strong storm at sea. Maximum wave height up to 7.5 m, average - 5.5 m
Storm	19-21	68-76	37-42	9	Large trees are bending, the wind is tearing tiles from the roofs, very strong sea waves, high waves (maximum height - 10 m, average - 7 m)
Heavy storm	22-25	79-90	43-49	10	Rarely on dry land. Significant destruction of buildings, the wind knocks down trees and uproots them, the surface of the sea is white with foam, a strong roar of waves is like blows, very high waves (maximum height - 12.5 m, average - 9 m)
Violent storm	26-29	94-104	50-56	11	It is observed very rarely. Accompanied by destruction in large spaces. At sea, exceptionally high waves (maximum height - up to 16 m, average - 11.5 m), small vessels are sometimes hidden from view
Hurricane	Over 29	Over 104	Over 56	12	Serious destruction of capital buildings

Meteorological dangerous phenomena- natural processes and phenomena that occur in the atmosphere under the influence of various natural factors or their combinations, which have or may have a damaging effect on people, farm animals and plants, economic facilities and the natural environment.

Wind - this is the movement of air parallel to the earth's surface, resulting from the uneven distribution of heat and atmospheric pressure and directed from a high pressure zone to a low pressure zone.

The wind is characterized by:
1. Wind direction - determined by the azimuth of the side of the horizon, from where
it blows, and is measured in degrees.
2. Wind speed - measured in meters per second (m/s; km/h; miles/hour)
(1 mile = 1609 km; 1 nautical mile = 1853 km).
3. Wind force - measured by the pressure that it exerts on 1 m2 of surface. The strength of the wind varies almost proportional to the speed,
therefore, the strength of the wind is often estimated not by pressure, but by speed, which simplifies the perception and understanding of these quantities.

Many words are used to indicate the movement of the wind: tornado, storm, hurricane, storm, typhoon, cyclone and many local names. To systematize them, all over the world use Beaufort scale, which allows you to very accurately estimate the strength of the wind in points (from 0 to 12) according to its effect on ground objects or on waves in the sea. This scale is also convenient in that it allows, according to the signs described in it, to fairly accurately determine the wind speed without instruments.

Beaufort scale (Table 1)

Points Beaufort	Verbal definition wind force	Wind speed, m/s (km/h)	The action of the wind on land
			On the land	On the sea
		0,0 – 0,2 (0,00-0,72)	Calm. Smoke rises vertically	Mirror-smooth sea
	Quiet breeze	0,3 –1,5 (1,08-5,40)	The direction of the wind can be seen from the drift of the smoke,	Ripples, no foam on the ridges
	light breeze	1,6 – 3,3 5,76-11,88)	The movement of the wind is felt by the face, the leaves rustle, the weather vane moves	Short waves, crests do not tip over and appear glassy
	Weak breeze	3,4 – 5,4 (12,24-19,44)	Leaves and thin branches of trees sway, the wind blows the top flags	Short well defined waves. Combs, tipping over, form foam, occasionally small white lambs are formed.
	moderate breeze	5,5 –7,9 (19,8-28,44)	The wind raises dust and pieces of paper, sets in motion the thin branches of trees.	The waves are elongated, white lambs are visible in many places.
	fresh breeze	8,0 –10,7 (28,80-38,52)	Thin tree trunks sway, waves with crests appear on the water	Well developed in length, but not very large waves, white lambs are visible everywhere.
	strong breeze	10,8 – 13,8 (38,88-49,68)	The thick branches of the trees are swaying, the wires are buzzing	Large waves begin to form. White foamy ridges occupy large areas.
	strong wind	13,9 – 17,1 (50,04-61,56)	Tree trunks sway, it's hard to go against the wind	Waves pile up, crests break, foam falls in stripes in the wind
	Very strong wind storm)	17,2 – 20,7 (61,92-74,52)	The wind breaks the branches of trees, it is very difficult to go against the wind	Moderately high, long waves. On the edges of the ridges, spray begins to take off. Strips of foam fall in rows in the wind.
	Storm (strong storm)	20,8 –24,4 (74,88-87,84)	Minor damage; the wind rips off the smoke caps and roof tiles	high waves. Foam in wide dense stripes lays down in the wind. The crests of the waves overturn and crumble into spray.
	Heavy storm (full storm)	24,5 –28,4 (88,2-102,2)	Significant destruction of buildings, trees uprooted. Rarely on land	Very high waves with long bends ridges down. The foam is blown up by the wind in large flakes in the form of thick stripes. The surface of the sea is white with foam. The roar of the waves is like blows. Visibility is poor.
	Violent storm (hard storm)	28,5 – 32,6 (102,6-117,3)	Large destruction over a large area. Very rare on land	Exceptionally high waves. Vessels are sometimes out of sight. The sea is covered with long flakes of foam. The edges of the waves are everywhere blown into foam. Visibility is poor.
		32.7 and more (117.7 and over)	Heavy objects are carried by the wind over long distances.	The air is filled with foam and spray. The sea is all covered with strips of foam. Very poor visibility.

Breeze (light to strong breeze) sailors refer to the wind as having a speed of 4 to 31 miles per hour. In terms of kilometers (factor 1.6) it will be 6.4-50 km/h

Wind speed and direction determine weather and climate.

Strong winds, significant changes in atmospheric pressure and a large number of precipitation causes dangerous atmospheric whirlwinds (cyclones, storms, squalls, hurricanes) that can cause destruction and loss of life.

Cyclone is the general name for eddies with reduced pressure in the center.

An anticyclone is an area of ​​high pressure in the atmosphere with a maximum in the center. In the Northern Hemisphere, the winds in the anticyclone blow counterclockwise, and in the Southern Hemisphere - clockwise, in the cyclone the wind movement is reversed.

Hurricane - wind of destructive force and considerable duration, the speed of which is equal to or exceeds 32.7 m/s (12 points on the Beaufort scale), which is equivalent to 117 km/h (Table 1).
In half of the cases, the wind speed during a hurricane exceeds 35 m/s, reaching up to 40-60 m/s, and sometimes up to 100 m/s.

Hurricanes are classified into three types based on wind speed:
- Hurricane (32 m/s and more),
- strong hurricane (39.2 m/s or more)
- fierce hurricane (48.6 m/s and more).

Cause of these hurricane winds is the occurrence, as a rule, on the line of collision of the fronts of warm and cold air masses, powerful cyclones with a sharp pressure drop from the periphery to the center and with the creation of a vortex air flow moving in the lower layers (3-5 km) in a spiral towards the middle and up, in the northern hemisphere, counterclockwise.

Such cyclones, depending on the place of their occurrence and structure, are usually divided into:
- tropical cyclones found over warm tropical oceans, usually moves westward during formation, and curves poleward after formation.
A tropical cyclone that reaches unusual strength is called hurricane if he is born in the Atlantic Ocean and adjacent seas; typhoon - in the Pacific Ocean or its seas; cyclone - in the region indian ocean.
mid-latitude cyclones can form both over land and over water. They usually move from west to east. characteristic feature such cyclones is their great "dryness". The amount of precipitation during their passage is much less than in the zone of tropical cyclones.
The European continent is affected by both tropical hurricanes that originate in the central Atlantic and cyclones of temperate latitudes.
Storm – a type of hurricane, but has a lower wind speed 15-31
m/sec.

The duration of storms is from several hours to several days, the width is from tens to several hundreds of kilometers.
Storms are divided into:

2. Stream storms – These are local phenomena of small distribution. They are weaker than whirlwinds. They are subdivided:
- stock - the air flow moves down the slope from top to bottom.
- Jet - characterized by the fact that the air flow moves horizontally or up the slope.
Stream storms pass most often between chains of mountains connecting valleys.
Depending on the color of the particles involved in the movement, black, red, yellow-red and white storms are distinguished.
Depending on the wind speed, storms are classified:
- storm 20 m/s and more
- strong storm 26 m/s and more
- severe storm of 30.5 m/s and more.

Squall – a sharp short-term increase in wind up to 20–30 m/s and higher, accompanied by a change in its direction associated with convective processes. Despite the short duration of squalls, they can lead to catastrophic consequences. Squalls in most cases are associated with cumulonimbus (thunderstorm) clouds, either local convection or a cold front. A squall is usually associated with heavy rainfall and thunderstorms, sometimes with hail. Atmospheric pressure during a squall rises sharply due to the rapid precipitation, and then falls again.

If possible, limit the area of ​​impact, all of the listed natural disasters are classified as non-localized.

Dangerous consequences of hurricanes and storms.

Hurricanes are one of the most powerful forces of the elements and, in terms of their detrimental effects, are not inferior to such terrible natural disasters as earthquakes. This is due to the fact that hurricanes carry enormous energy. Its amount released by a hurricane of average power during 1 hour is equal to the energy of a nuclear explosion of 36 Mt. In one day, the amount of energy that would be enough to provide electricity to a country like the United States is released. And in two weeks (the average duration of the existence of a hurricane), such a hurricane releases energy equal to the energy of the Bratsk hydroelectric power station, which it can generate in 26 thousand years. The pressure in the hurricane zone is also very high. It reaches several hundred kilograms per square meter a fixed surface perpendicular to the direction of the wind.

The hurricane destroys strong and demolishes light buildings, devastates sown fields, breaks wires and knocks down power lines and communication poles, damages highways and bridges, breaks and uproots trees, damages and sinks ships, causes accidents on public energy networks, in production. There are cases when hurricane winds destroyed dams and dams, which led to large floods, threw trains off the rails, tore bridges off their supports, knocked down factory pipes, and threw ships onto land. Hurricanes are often accompanied by heavy downpours, which are more dangerous than the hurricane itself, as they cause mudflows and landslides.

Hurricanes vary in size. Usually, the width of the zone of catastrophic destruction is taken as the width of the hurricane. Often, the area of ​​storm force winds with relatively little damage is added to this zone. Then the width of the hurricane is measured in hundreds of kilometers, sometimes reaching 1000 km. For typhoons, the destruction zone is usually 15-45 km. The average duration of a hurricane is 9-12 days. Hurricanes occur at any time of the year, but most often from July to October. In the remaining 8 months they are rare, their paths are short.

The damage caused by a hurricane is determined by a whole complex of various factors, including the terrain, the degree of development and the strength of buildings, the nature of vegetation, the presence of population and animals in its area of ​​action, the time of year, preventive measures taken and a number of other circumstances, the main of which is velocity head of the air flow q, proportional to the product of the density atmospheric air per square of air flow velocity q = 0.5pv 2.

According to building codes and the rules, the maximum standard value of wind pressure is q = 0.85 kPa, which, at an air density of r = 1.22 kg/m3, corresponds to wind speed.

For comparison, we can cite the calculated values ​​of the velocity head used to design nuclear power plants for the Caribbean region: for buildings of category I - 3.44 kPa, II and III - 1.75 kPa and for open installations - 1.15 kPa.

Every year, about a hundred powerful hurricanes march through the globe, causing destruction and often taking away human lives(Table 2). On June 23, 1997, a hurricane swept over most of the Brest and Minsk regions, as a result of which 4 people died and 50 were injured. In the Brest region, 229 settlements were de-energized, 1071 substations were disabled, roofs were torn off from 10-80% residential buildings in more than 100 settlements, up to 60% of buildings of agricultural production were destroyed. In the Minsk region, 1,410 settlements were de-energized, hundreds of houses were damaged. Broken and uprooted trees in forests and forest parks. At the end of December 1999, Belarus also suffered from a hurricane wind that swept across Europe. Power lines were cut, many settlements were de-energized. In total, 70 districts and more than 1,500 settlements were affected by the hurricane. Only in the Grodno region, 325 transformer substations failed, in the Mogilev region even more - 665.

table 2
Impact of some hurricanes

Location of the crash, year	Death toll	Number of wounded	Associated phenomena
Haiti, 1963		Not fixed
		Not fixed
Honduras, 1974		Not fixed
Australia, 1974
Sri Lanka, 1978		Not fixed
Dominican Republic, 1979
		Not fixed
Indochina, 1981		Not fixed	Flood
Bangladesh, 1985		Not fixed	Flood

Tornado (tornado)- whirlwind movement of air, propagating in the form of a giant black column with a diameter of up to hundreds of meters, inside which there is a rarefaction of air, where various objects are drawn.

Tornadoes occur both over the water surface and over land, much more often than hurricanes. Very often they are accompanied by thunderstorms, hail and showers. The speed of air rotation in the dust column reaches 50-300 m/s and more. During its existence, it can travel a distance of up to 600 km - along a strip of terrain several hundred meters wide, and sometimes up to several kilometers, where destruction occurs. The air in the column rises in a spiral and draws in dust, water, objects, people.
Dangerous factors: buildings caught in a tornado due to a vacuum in the air column are destroyed from the pressure of air from the inside. It uproots trees, overturns cars, trains, lifts houses into the air, etc.

Tornadoes in Belarus occurred in 1859, 1927 and 1956.

Absolutely non-flying weather from the point of view of the passenger, it can be only a minor inconvenience for the pilot, while at the same time, quite tolerable weather in the traditional sense can be non-flying. Of course, in the latter case, delays and cancellations of flights cause understandable anger on the part of the passenger. In fact, a number of meteorological phenomena can interfere with the safe operation of a flight. It often happens that flights of some airlines take off and land, while others wait for hours for the weather or are canceled altogether. We have already touched on the topic of weather conditions in, in this article we will talk in more detail about what kind of weather and how it affects aviation activities, what is meteorological minimum and how the crew decides to take off.

So, let's start with the fact that before trying to determine whether the weather is flying or not, you need to establish the appropriate criterion. This criterion is called meteorological minimum, takeoff and landing minima apply to wind speed and direction, visibility, cloud base, runway conditions.

As such, there are no minima for flying along the route, but we must not forget that there are a number of meteorological conditions that are a priori dangerous for aviation, we are talking primarily about thunderstorms and related phenomena, such as hail, lightning, heavy icing, severe turbulence. Of course, most thunderstorms can be bypassed, but when it comes to frontal thunderstorms that stretch for hundreds of kilometers like a solid wall, it is often not possible to bypass them.

As a rule, when talking about minima, we are talking about the minimum visibility on the runway and the decision height (CHL). Decision Height is the height at which the pilot must perform a go-around if he cannot see the runway.

There are three types of minima:

• Aircraft minimum.

  This is the minimum set by the aircraft manufacturer, that is, a list of acceptable weather conditions under which the manufacturer guarantees safe operation aircraft.

• Airfield minimum.

  This is the minimum set at this airport for each particular runway. It depends on the ground-based radio navigation, lighting and technical equipment installed at the airport and the terrain surrounding the airport (mainly the terrain and artificial obstacles).

• Crew minimum.

  The crew minimum is the personal admission of each pilot to perform a flight in certain weather conditions. Pilot minimums are achieved by passing a special training program and confirmed by flight checks.

The basic rule for the application of meteorological minima is that the worst minimum of the three is applied: airplane, airport, and crew.

Let's take an example. The aircraft manufacturer set the minimum visibility on the landing strip for this aircraft at 200 meters, the crew confirmed their qualifications as a result of checks and has a landing clearance with a horizontal visibility of 200 meters, however, for the aerodrome on which the flight is performed, a minimum of 800 meters is set. As mentioned above, the worst minimum is selected, that is, in this case, a minimum of 800 meters will be applied. Everything is extremely logical, in this case, despite the excellent equipment of the aircraft and the high qualification of the pilots, the airport has less advanced equipment that will not allow you to perform a landing approach with such high accuracy, so the final minimum will correspond to the minimum of the airfield.

Let's talk in more detail about weather phenomena that limit the activities of aviation.

Visibility.

Probably the most common reason for weather delays is limited visibility. This group includes such meteorological phenomena as fog, rain, snow, dust, smoke, in general, everything that somehow reduces visibility. From an aviation point of view, it is not particularly important what the visibility is limited to, the main parameter determining the possibility of taking off and landing is the runway visual range, or RVR (Runway visual range). The second landing minimum parameter is decision height. For example, 60x550, where 60 meters is the decision height and 550 meters is the runway visual range. Sometimes a third parameter is added - the height of the cloud base.

As already mentioned, the minimum airfield depends, among other things, on the radio navigation equipment of the runway, most often on the category of the course-glide path landing system ILS. Most Russian airports have a basic ILS system of the first category, which provides a minimum 60x550, often the airfield is not equipped with a HUD at all, then the landing approach is carried out according to the so-called inaccurate systems and the airfield minimum is much higher. ILS equipment of the second category is currently installed at several airports in the Russian Federation such as Ufa, Vnukovo, Novosibirsk, Krasnoyarsk, the minimum is 30x300 meters. And only three airports have Category IIIA HUD equipment, the minimum for which is 15x200 meters, these are Sheremetyevo, Domodedovo and Pulkovo.

Mountain airfields are a special case, where the minima can be much higher despite the ground equipment installed.

If we talk about aircraft minimums, then most of the foreign-made aircraft, which are the majority today, are allowed to fly under the category IIIB and IIIC, that is, they can land in automatic mode when visibility is close to zero, but in Russia so far not a single airport has the appropriate equipment, which is not surprising because of its huge cost. As for the pilots, most of them have a landing clearance of at least 15x200, less often you can meet crews with a 60x550 clearance, as a rule, these are those who have only recently performed solo flights.

Airport minimums for takeoff depend mainly on the characteristics of the lighting and technical equipment of the runway and obstacles around the runway and are usually about 150-250 meters.

Wind.

Usually, the wind limits are the limits set by the aircraft manufacturer, very rarely airport regulations require these values ​​to be adjusted upwards. The wind speed is decomposed into two components - lateral and longitudinal. Airplanes are taking off and landing against the wind, or with a small associated component. The reason for this is security, because take-off and landing against the wind can significantly reduce the speed of landing and take-off, and therefore reduce the take-off and run distances. For most modern civil aircraft, the maximum tailwind component during takeoff and landing is 5 meters per second, and the side wind component is about 17-18 meters per second.

The wind speed of 11 m/s is decomposed into two components: lateral and tailwind.

side wind is dangerous, because in order to compensate for it, it is necessary to turn the aircraft slightly against the wind, to the so-called drift angle the stronger the wind, the larger this angle. While the plane is flying, drift does not cause problems, but at the moment it touches the runway, the plane acquires grip with its surface and tends to move in a direction parallel to its axis, at this moment the pilot needs to sharply change the direction of movement, which is not always easy. Of particular danger is the gusty wind, which can “blow” at the most inopportune moment, creating a large roll, which is very dangerous in conditions of proximity to the ground.

Landing with a strong side wind.

Recall that we are talking about the wind components decomposed for a particular runway direction, the value of the wind speed itself can be much higher.

Wind that would blow strictly perpendicular to the runway at a speed of about 20 meters per second is an infrequent phenomenon, usually such a strong wind is associated with the passage of powerful cyclones. As for the tailwind, for the vast majority of airports this problem is solved by simply changing the operating threshold of the runway, but there are a number of airports where this is not possible. For example, Sochi and Gelendzhik. These airfields are located in close proximity to the mountains, which excludes the possibility of taking off towards the mountains and landing from the side of the mountains, that is, you need to take off at sea. If the wind blows towards the sea, often the tail component excludes the possibility of a safe takeoff. That is, in fact, you can sit down, but you can’t take off anymore.

Adler Airport in Sochi.

Runway condition.

If the runway is covered with a layer of ice, whatever one may say, it is impossible to take off and land. In aviation, such a concept is used as adhesion coefficient, which is regularly measured by the aerodrome service, if its value falls below 0.3, the runway is not suitable for takeoff and landing. In case there is a side wind, this threshold value is adjusted upwards. A friction coefficient below 0.29 means that the lane is covered with a layer of ice, snow or slush and needs cleaning. Unfavorable weather conditions such as heavy snowfall or freezing precipitation can derail all runway clearance work, causing the airfield to be closed for many hours.

How is the decision to fly made?

The decision to take off is the exclusive right of the aircraft commander. To decide to fly or not to fly, first of all, you need to familiarize yourself with the meteorological information on the aerodromes of departure, destination and alternate. For this, weather reports of the actual weather are used. METAR, which are issued for all airports with a frequency of 30 minutes and forecasts TAF, the frequency of release of which is usually 3 or 6 hours. METAR and TAF reflect in standard form all meteorological information that is somehow significant when flying to a given aerodrome.

As an example, let's take the METAR of Krasnoyarsk Airport:

UNKL 181830Z 00000MPS 4600 BCFG SCT046 BKN240 11/09 Q1012 TEMPO 0500 FG RMK QFE733 29////65

For an uninitiated person, this is just a set of letters and numbers, but one glance is enough for a pilot to understand that the weather is “not very good”. The following information is encoded in the report: at the Krasnoyarsk airfield on the 18th at 18:30 UTC, the following conditions existed: wind - calm, visibility 4600m, fog in places, scattered clouds at 1500 meters, broken at 800 meters, temperature 11 degrees, dew point 9 degrees, fog at times with visibility of 500 meters, pressure 733 millimeters of mercury column, friction coefficient on the runway 0.65.

When deciding on a departure, all flights are conditionally divided into two categories: less than two hours and more than two hours. For flights less than two hours, it is allowed to ignore the forecast and take off if the actual weather at the moment is above the minimum. If the flight lasts more than two hours, on the contrary, the actual weather at the aerodrome is not taken into account, and the decision is made based on the TAF forecast. By the way, Russian legislation allows you to make a decision to take off if the weather at the destination airfield is predicted to be below the minimum if there are two alternate airfields with acceptable weather conditions, but this opportunity is rarely used, which is quite reasonable.

Why do some take off and land, while others wait for the weather?

There are many reasons. Let's give examples. For example, fog below the minimum is predicted in Samara, while the actual weather is still above the minimum. Flights from Moscow take off and land, and flights from St. Petersburg are delayed. The fact is that the flight from Moscow lasts less than two hours, and the decision to take off is made based on actual conditions, while the flight from St. Petersburg takes more than two hours, which means that it will be possible to fly only under the predicted improvement.

Some sat down, while others went to the alternate airfield, why? Again, different planes, different crews. It is possible that the flight that was diverted was operated by a crew with a poor personal minimum, or the aircraft was not allowed to land in these conditions. By the way, even two outwardly identical aircraft of the same manufacturer may have different restrictions, for example, some A320 aircraft are allowed to operate with a tailwind component of 7 meters per second, while the rest have a limit of 5 meters per second.

Often, from passengers waiting for the departure of a flight delayed due to weather conditions, one can hear statements like “I just called my aunt, she said that there is no fog and never was! We are being deceived!" We hasten to assure that no one is deceiving anyone. For some reason, many citizens think that if there is fog in Sheremetyevo, then all of Moscow, exactly along its border, should be covered with fog. Not at all. Many weather events are very local in nature. It happens that visibility on parallel runways differs by several kilometers.