Is the wind strong 2 m s. Technical Library

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- N, northeast - NE, etc.), or in the corners (relative to the meridian, north - 360 ° or 0 °, east - 90 °, south - 180 °, west - 270 °), fig. 1.

// Classification of wind strength, sea waves, and visibility at sea

Classification of wind strength, sea waves, and visibility at sea

Beaufort scale

0 points - calm
A mirror-smooth sea, almost motionless. Waves practically do not run up to the shore. The water is more like a quiet backwater of a lake than sea ​​coast. Haze may be observed above the surface of the water. The edge of the sea merges with the sky so that the border is not visible. Wind speed 0-0.2 km/h.

1 point - quiet
Light ripples on the sea. The height of the waves reaches up to 0.1 meters. The sea can still merge with the sky. There is a light, almost imperceptible breeze.

2 points - easy
Not big waves, not more than 0.3 meters high. The wind speed is 1.6-3.3 m/s, you can feel it with your face. With such a wind, the weather vane begins to move.

3 points - weak
Wind speed 3.4-5.4 m/s. Slight roughness on the water, occasionally lambs appear. The average wave height is up to 0.6 meters. A weak surf is clearly visible. The weather vane spins without frequent stops, the leaves on the trees, flags and so on sway.

4 points - moderate
Wind - 5.5 - 7.9 m / s - raises dust and small pieces of paper. The weather vane spins continuously, the thin branches of the trees bend. The sea is restless, in many places lambs are visible. Wave height up to 1.5 meters.

5 points - fresh
Almost the entire sea is covered with white lambs. Wind speed 8 - 10.7 m/s, wave height 2 meters. Branches and thin tree trunks sway.

6 points - strong
The sea in many places is covered with white ridges. The height of the waves reaches 4 meters, the average height is 3 meters. Wind speed 10.8 - 13.8 m/s. Thin tree trunks bend, and thick branches of trees, telephone wires buzz.

7 points - strong
The sea is covered with white foamy ridges, which are blown off the surface of the water from time to time by the wind. The wave height reaches 5.5 meters, the average height is 4.7 meters. Wind speed 13.9 - 17.1 m/s. Medium tree trunks sway, branches bend.

8 points - very strong
Strong waves, foam on each crest. The height of the waves reaches 7.5 meters, the average height is 5.5 meters. Wind speed 17.2 - 20 m/s. It is difficult to go against the wind, it is almost impossible to talk. Thin branches of trees break.

9 points - storm
High waves on the sea, reaching 10 meters; average height 7 meters. Wind speed 20.8 - 24.4 m/s. Large trees bend, medium branches break. The wind rips off poorly reinforced roof coverings.

10 points - strong storm
The sea is white. Waves crash on the shore or on the rocks with a crash. The maximum wave height is 12 meters, the average height is 9 meters. The wind, at a speed of 24.5 - 28.4 m/s, rips off roofs, significant damage to buildings.

11 points - fierce storm
High waves reach 16 meters, with an average height of 11.5 meters. Wind speed 28.5 - 32.6 m/s. Accompanied by great destruction on land.

12 points - hurricane
Wind speed 32.6 m/s. Serious damage to capital buildings. The wave height is over 16 meters.

Sea wave scale

In contrast to the generally accepted twelve-point system for estimating wind, there are several estimates of sea waves. British, American and Russian grading systems are generally accepted. All scales are based on a parameter that determines average height significant waves (according to the site savelyev.info). This setting is called Significance Wave Height (SWH). In the American scale, 30% of significant waves are taken, in the British 10%, in the Russian 3%. Wave height is measured from the crest (the top of the wave) to the trough (the base of the trough).
Below is a description of the height of the waves.

0 points - calm
1 point - ripples (SWH< 0,1 м)
2 points - weak waves (SWH 0.1 - 0.5 m)
3 points - light waves (SWH 0.5 - 1.25 m)
4 points - moderate waves (SWH 1.25 - 2.5 m)
5 points - rough sea (SWH 2.5 - 4.0 m)
6 points - very rough sea (SWH 4.0 - 6.0 m)
7 points - strong sea (SWH 6.0 - 9.0 m)
8 points - very strong sea (SWH 9.0 - 14.0 m)
9 points - phenomenal sea (SWH > 14.0 m)
In this scale, the word "storm" is not applicable. Since it is not determined by the strength of the storm, but by the height of the wave. Storm is defined by Beaufort.
For the WH parameter for all scales, it is precisely a part of the waves (30%, 10%, 3%) that is taken because the magnitude of the waves is not the same. At a certain time interval there are waves, for example, 9 meters, as well as 5, 4, etc. Therefore, each scale has its own SWH value, where a certain percentage of the highest waves is taken. There are no instruments for measuring wave height. Therefore, there is no exact definition of the score. The definition is conditional.
On the seas, as a rule, the wave height reaches 5-6 meters in height, and up to 80 meters in length.

Visibility scale

Visibility is the maximum distance at which objects are detected during the day and navigation lights at night. Visibility depends on weather conditions. In metrology, the influence of weather conditions on visibility is determined by a conditional scale of points. This scale is a way of indicating the transparency of the atmosphere. Distinguish between day and night visibility. Below is a daily scale for determining the range of visibility.
Up to 1/4 cable
About 46 meters. Very poor visibility. Thick fog or blizzard.
Up to 1 cable
About 185 meters. Bad visibility. Thick fog or sleet.
2-3 cables
370 - 550 meters. Bad visibility. Fog, wet snow.
1/2 mile
About 1 km. Haze, thick haze, snow.
1/2 - 1 mile
1 - 1.85 km. Average visibility. Snow, heavy rain
1 - 2 miles
1.85 - 3.7 km. Haze, mist, rain.
2 - 5 miles
3.7 - 9.5 km. Light haze, haze, light rain.
5 - 11 miles
9.3 - 20 km. Good visibility. Visible horizon.
11 - 27 miles
20 - 50 km. Very good visibility. The horizon is clearly visible.
27 miles
Over 50 km. Exceptional visibility. The horizon is clearly visible, the air is transparent.

Many people ask the question: at what wind speed do planes not fly? Indeed, there are certain speed limits. Compared to the speed of the aircraft, which reaches 250 m/s, even a strong wind with a speed of 20 m/s will not interfere with the aircraft during flight. However, a crosswind can interfere with an airliner when it is moving at a slower speed, namely at the time of takeoff or landing. Therefore, under such conditions, planes do not take off. Air currents affect the speed of the aircraft, the direction of movement, as well as the length of the roll and takeoff run. In the atmosphere, these streams are present at all altitudes. This movement of air in relation to a flying airliner is a portable movement. If a strong wind is blowing, the direction of movement of the airliner in relation to the ground does not coincide with the longitudinal axis of the aircraft. Strong air currents can blow the plane off course.

Airliners always land and take off against the direction of the wind. In the case of takeoff or landing with a tailwind, the length of the takeoff run and run increases significantly. When taking off or landing, an airliner penetrates the lower atmosphere so quickly that the pilot does not have time to respond to a change in the wind. If he does not know about a sharp increase or, conversely, a weakening of air flows in the lower layers of the atmosphere, this is fraught with a plane crash.

During takeoff, when an airliner is gaining altitude, it enters a zone of strong headwind. As the aircraft climbs, the lift force of the aircraft increases. Moreover, the increase occurs faster than the pilot can control it. The flight path in this case may be higher than the calculated one. If there is a sharp increase in wind, this can cause the airliner to fall into a supercritical angle of attack. This can lead to airflow stall and collision with the ground.

Generally, the allowable maximum wind force is determined for each aircraft individually, depending on the specifics of its specific characteristics and technical capabilities. Sets the maximum wind speed at which takeoff or landing can be made, by the manufacturer of the airliner. More precisely, the manufacturer sets two maximum speeds: passing and lateral. Tail speed for most modern airliners is the same. During takeoff and landing, the tail speed must not exceed 5 m/s. As for the lateral speed, it is different for each airliner:

• for TU-154 aircraft - 17 m/s;
• for AN-24 - 12 m/s;
• for TU-134 - 20 m/s.

On average, airliners are set to the maximum lateral speed 17 m/s. At more speed the vast majority of aircraft do not take off. If there is a sharp increase in wind in the arrival area, the speed of which exceeds the permissible values, the planes do not land at this airport, but make emergency landing to another runway where conditions allow the aircraft to land safely.

Answering the question in what wind the planes do not fly, it can be said with confidence that at a speed of more than 20 m / s, if the wind blows perpendicular to the runway, takeoff cannot be carried out. Such a strong wind is associated with the passage of powerful cyclones. Below you can watch a video of landing an aircraft in a strong crosswind to see how difficult it is to do even for a professional experienced pilot with a long experience. Of particular danger in this case is the gusty wind in the lower layers of the atmosphere. It can begin to blow at the most inopportune moment, forming a large roll, which poses a great danger to the aircraft.

Crosswind is dangerous because it requires the pilot to take certain actions that are very difficult to perform. In aviation, there is such a thing as a "drift angle". This term refers to the amount of angle an airliner deviates from a given direction due to the wind. The stronger the wind, the larger this angle. Accordingly, the more effort the pilot needs to make to turn the airliner to this angle in reverse side. As long as the aircraft is in flight, even such a strong wind does not cause any problems. But as soon as the plane makes contact with the surface of the runway, the airliner acquires traction and begins to move in a direction parallel to its axis. At this moment, the pilot must abruptly change the direction of the aircraft, which is very difficult.

As for the problem of a strong tailwind, it is easily solved by changing the operating threshold of the runway. However, not every airport has such an opportunity. For example, Sochi and Gelendzhik are deprived of such an opportunity. If a strong wind blows towards the sea, landing can be carried out, but taking off under such conditions is unsafe. That is, the landing of the aircraft at strong wind possible, but not in all cases.

Runway condition

Even if the wind speed allows you to take off or land, there are still a number of factors that can affect the final decision. In particular, in addition to weather conditions, visibility, the condition of the runway is taken into account. If it is covered with ice, landing or takeoff cannot be carried out. In aviation, there is such a term as "traction coefficient". If this indicator is below 0.3, this runway strip unsuitable for landing or takeoff and needs to be cleaned. If the decrease in friction coefficient was due to heavy snowfall, in which cleaning is not possible, the entire airport is closed until the weather improves. Such a break in work can last several hours.

How is the decision to take off made?

This decision must be made by the aircraft commander. To do this, first of all, he must familiarize himself with the meteorological data on the air hubs of departure, landing and alternate airports. For this, METAR and TAF forecasts are used. The first forecast is issued for all airports every half hour. The second is given every 3-6 hours. Such forecasts reflect all relevant information that may influence the decision to take off or cancel a flight. In particular, such forecasts contain data on wind speed and its changes.

To make a decision, all flights are conditionally divided into 2-hour and longer ones. If the flight lasts less than two hours, it is enough for the actual weather to be acceptable (above the minimum) for takeoff. If the flight is longer, the TAF forecast must be additionally taken into account. If the weather conditions at the destination do not allow landing, in some cases, the decision to take off may be positive. For example, if the weather conditions at the destination are below the minimum, however, there are two aerodromes in the immediate vicinity with optimal weather conditions. But a positive decision is almost never made in these cases, given the danger of such a flight.

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Wind is the movement of air in a horizontal direction along the earth's surface. In which direction it blows depends on the distribution of pressure zones in the planet's atmosphere. The article deals with issues related to the speed and direction of the wind.

Perhaps, absolutely calm weather will be a rare phenomenon in nature, since you can constantly feel that a light breeze is blowing. Since ancient times, mankind has been interested in the direction of air movement, so the so-called weather vane or anemone was invented. The device is an arrow freely rotating on a vertical axis under the influence of wind force. She points his direction. If you determine the point on the horizon from which the wind blows, then the line drawn between this point and the observer will show the direction of air movement.

In order for an observer to convey information about the wind to other people, concepts such as north, south, east, west and their various combinations are used. Since the totality of all directions forms a circle, the verbal formulation is also duplicated by the corresponding value in degrees. For example, north wind means 0 o (the blue compass needle points due north).

The concept of the wind rose

Speaking about the direction and speed of movement of air masses, a few words should be said about the wind rose. It is a circle with lines showing how air flows. The first mention of this symbol was found in the books of the Latin philosopher Pliny the Elder.

The entire circle, reflecting the possible horizontal directions of the forward movement of air, is divided into 32 parts on the wind rose. The main ones are north (0 o or 360 o), south (180 o), east (90 o) and west (270 o). The resulting four parts of the circle are divided further, forming the northwest (315 o), northeast (45 o), southwest (225 o) and southeast (135 o). The resulting 8 parts of the circle are again divided in half each, which forms additional lines on the wind rose. Since the result is 32 lines, the angular distance between them is equal to 11.25 o (360 o /32).

Note that distinctive feature The wind rose is an image of a fleur-de-lis located above the north icon (N).

Where does the wind blow from?

Horizontal movements of large air masses are always carried out from areas of high pressure to areas of lower air density. At the same time, you can answer the question of what wind speed is by studying the location on geographical map isobars, that is, broad lines within which air pressure is constant. The speed and direction of movement of air masses is determined by two main factors:

• The wind always blows from the areas where the anticyclone stands to the areas covered by the cyclone. This can be understood if we remember that in the first case we are talking about zones of high pressure, and in the second case - low pressure.
• Wind speed is in direct proportion to the distance that separates two adjacent isobars. Indeed, the greater this distance, the weaker the pressure drop will be felt (in mathematics they say a gradient), which means that the forward movement of air will be slower than in the case of small distances between isobars and large pressure gradients.

Factors affecting wind speed

One of them, and the most important one, has already been voiced above - this is the pressure gradient between neighboring air masses.

In addition, the average wind speed depends on the topography of the surface over which it blows. Any irregularities in this surface significantly hinder the forward movement of air masses. For example, everyone who has been in the mountains at least once should have noticed that the winds are weak at the foot. The higher you climb the mountainside, the stronger the wind is felt.

For the same reason, winds blow stronger over the sea than over land. It is often eroded by ravines, covered with forests, hills and mountain ranges. All these heterogeneities, which are not over the seas and oceans, slow down any gusts of wind.

High above the earth's surface (on the order of several kilometers) there are no obstacles to the horizontal movement of air, so the wind speed in the upper troposphere is high.

Another factor that is important to consider when talking about the speed of movement of air masses is the Coriolis force. It is generated due to the rotation of our planet, and since the atmosphere has inertial properties, any movement of air in it is deflected. Due to the fact that the Earth rotates from west to east around its own axis, the action of the Coriolis force leads to the deviation of the wind to the right in the northern hemisphere, and to the left in the southern.

Curiously, this effect of the Coriolis force, which is negligible at low latitudes (tropics), has a strong influence on the climate of these zones. The fact is that the slowdown in wind speed in the tropics and at the equator is compensated by an increase in updrafts. The latter, in turn, lead to the intense formation of cumulus clouds, which are sources of strong tropical showers.

Instrument for measuring wind speed

It is an anemometer, which consists of three cups located at an angle of 120 o relative to each other, and fixed on a vertical axis. The principle of operation of an anemometer is quite simple. When the wind blows, the cups experience its pressure and begin to rotate on the axis. The stronger the air pressure, the faster they spin. By measuring the speed of this rotation, one can accurately determine the wind speed in m/s (meters per second). Modern anemometers are equipped with special electrical systems that independently calculate the measured value.

The instrument of wind speed based on the rotation of the cups is not the only one. There is another simple tool called the pitot tube. This device measures the dynamic and static wind pressure, the difference between which can accurately calculate its speed.

Beaufort scale

Information about wind speed, expressed in meters per second or kilometers per hour, for most people - and especially for sailors - says little. Therefore, in the 19th century, the English admiral Francis Beaufort proposed to use some empirical scale for evaluation, which consists of a 12-point system.

The higher the Beaufort scale, the stronger the wind blows. For example:

• The number 0 corresponds to absolute calm. With it, the wind blows at a speed not exceeding 1 mph, that is, less than 2 km / h (less than 1 m / s).
• The middle of the scale (number 6) corresponds to a strong breeze, the speed of which reaches 40-50 km/h (11-14 m/s). Such a wind is capable of raising large waves on the sea.
• The maximum on the Beaufort scale (12) is a hurricane whose speed exceeds 120 km/h (more than 30 m/s).

Major winds on planet Earth

They are usually classified into one of four types in the atmosphere of our planet:

• Global. They are formed as a result of the different ability of continents and oceans to heat up from the sun's rays.
• Seasonal. These winds change with the season of the year, which determines how much solar energy a certain area of ​​the planet receives.
• Local. They are associated with features geographical location and topography of the area in question.
• Rotating. These are the strongest movements of air masses that lead to the formation of hurricanes.

Why is it important to study the winds?

In addition to the fact that information about wind speed is included in the weather forecast, which every inhabitant of the planet takes into account in his life, air movement plays an important role in a number of natural processes.

So, he is a carrier of plant pollen and is involved in the distribution of their seeds. In addition, wind is one of the main sources of erosion. Its destructive effect is most pronounced in deserts, when the terrain changes dramatically during the day.

It should also not be forgotten that the wind is the energy that people use in economic activity. According to general estimates, wind energy makes up about 2% of all solar energy falling on our planet.

In 1963, the World Meteorological Organization clarified Beaufort scale and it was adopted for an approximate estimate of wind speed by its effect on ground objects or by waves on the high seas. average speed wind is indicated at a standard height of 10 meters above an open flat surface.

The smoke (from the captain's pipe) rises vertically, the leaves of the trees are motionless. Mirror-like sea.

Wind 0 - 0.2m/s

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 0.1m.

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.

Wind 1.6 - 3.3m/s.

Leaves and thin branches of trees sway, light flags sway, slight excitement on the water, occasionally small lambs form.

The average wave height is 0.6 m. The wind is 3.4 - 5.4 m/s.

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. Wind 5.5 - 7.9 m/s.

Branches and thin tree trunks sway, the wind is felt by hand, white lambs are visible everywhere.

The maximum wave height is 2.5 m, the average is 2 m. The wind is 8.0 - 10.7 m/s.

In this weather, we tried to leave by Baltic Sea from Darlowo. (Poland) against the wave. In 30 minutes only approx. 10km. and very wet from the splashes. We returned along the way - och. funny.

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. The maximum wave height is up to 4m, the average is 3m. Wind 10.8 - 13.8m/s.

Such weather was caught on boats in front of Rostock. The navigator was afraid to look around, the most valuable thing was stuffed into his pockets, the radio was tied to his vest. Spray from the side waves constantly covered us. For a water-powered fleet, not to mention a simple motorboat, this is probably the maximum ...

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. The maximum wave height is up to 5.5m. wind 13.9 - 17.1 m/s.

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.

The maximum wave height is up to 7.5 m, the average is 5.5 m. The wind is 17.2 - 20.7 m / s.

Large trees are bending, the wind is tearing tiles from the roofs, very strong sea waves, high waves. It is observed very rarely. Accompanied by destruction in large spaces. At sea, there are exceptionally high waves (maximum height - up to 16m, average - 11.5m), small vessels are sometimes hidden from view.

Wind 28.5 - 32.6m/s. Violent storm.

The sea is all covered with strips of foam. The air is filled with foam and spray. Visibility is very poor. Full p ... ts small-sized ships, yachts and other ships - it's better not to get hit.

Wind 32.7 m/s or more...