Is strong wind dangerous for the aircraft. Beaufort scale - wind strength and sea conditions

Beaufort scale - a conditional scale that allows you to visually assess the approximate strength of the wind by its effect on ground objects or by waves at sea. Developed by the English admiral and hydrographer Francis Beaufort (Eng. Francis Beaufort) in 1806.

Since 1874, it has been officially accepted for use in international synoptic practice. Since 1926, the Beaufort scale has additionally indicated wind strength in meters per second at a height of 10 meters from the surface. In the USA, in addition to the international 12-point scale, since 1955, a scale expanded to 17 points has been used, which is used for more accurate gradation of hurricane winds.

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. 1.

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 a distinctive feature of the wind rose is the 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, it is possible to answer the question of what wind speed is by examining the location on the geographical map of isobars, that is, wide 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 increased 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 the features of the geographical location and topography of the area under consideration.
• 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.

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

The horizontal movement of air above the Earth's surface is called wind. The wind always blows from an area of ​​high pressure to an area of ​​low pressure.

Wind characterized by speed, strength and direction.

Wind speed and strength

Wind speed measured in meters per second or points (one point is approximately equal to 2 m/s). The speed depends on the baric gradient: the greater the baric gradient, the higher the wind speed.

The force of the wind depends on the speed (Table 1). The greater the difference between adjacent areas of the earth's surface, the stronger the wind.

Beaufort scale- a conditional scale for visual assessment of the strength (speed) of the wind in points according to its effect on ground objects or on waves at sea. It was developed by the English admiral F. Beaufort in 1806 and at first was used only by him. In 1874, the Standing Committee of the First Meteorological Congress adopted the Beaufort scale for use in International synoptic practice. In subsequent years, the scale has changed and refined. The Beaufort scale is widely used in marine navigation.

Direction of the wind

Direction of the wind is determined by the side of the horizon from which it blows, for example, the wind blowing from the south is south. The direction of the wind depends on the pressure distribution and on the deflecting effect of the Earth's rotation.

On the climate map, the prevailing winds are shown by arrows (Fig. 1). The winds observed near the earth's surface are very diverse.

You already know that the surface of land and water heats up in different ways. On a summer day, the land surface heats up more. From heating, the air above the land expands and becomes lighter. Over the pond at this time the air is colder and therefore heavier. If the reservoir is relatively large, on a quiet hot summer day on the shore you can feel a light breeze blowing from the water, above which it is higher than above land. Such a light breeze is called daytime. breeze(from the French brise - light wind) (Fig. 2, a). The night breeze (Fig. 2, b), on the contrary, blows from the land, since the water cools much more slowly and the air above it is warmer. Breezes can also occur at the edge of the forest. The scheme of breezes is shown in fig. 3.

Rice. 1. Scheme of distribution of prevailing winds on the globe

Local winds can occur not only on the coast, but also in the mountains.

Föhn- a warm and dry wind blowing from the mountains to the valley.

Bora- gusty, cold and strong wind that appears when cold air rolls over low ridges to the warm sea.

Monsoon

If the breeze changes direction twice a day - day and night, then seasonal winds - monsoons— change their direction twice a year (Fig. 4). In summer, the land warms up quickly, and the air pressure over its surface hits. At this time, cooler air begins to move to land. In winter, the opposite is true, so the monsoon blows from land to sea. With the change of the winter monsoon to the summer monsoon, dry, slightly cloudy weather changes to rainy.

The action of monsoons is strongly manifested in the eastern parts of the continents, where they are adjacent to vast expanses of oceans, so such winds often bring heavy rainfall to the continents.

The unequal nature of the circulation of the atmosphere in different regions of the globe determines the differences in the causes and nature of the monsoons. As a result, extratropical and tropical monsoons are distinguished.

Rice. 2. Breeze: a - daytime; b - night

Rice. Fig. 3. Scheme of breezes: a - in the afternoon; b - at night

Rice. 4. Monsoons: a - in summer; b - in winter

extratropical monsoons - monsoons of temperate and polar latitudes. They are formed as a result of seasonal fluctuations in pressure over the sea and land. The most typical zone of their distribution is the Far East, Northeast China, Korea, and to a lesser extent Japan and the northeastern coast of Eurasia.

tropical monsoons - monsoons of tropical latitudes. They are due to seasonal differences in the heating and cooling of the Northern and Southern hemispheres. As a result, pressure zones shift seasonally relative to the equator to the hemisphere in which it is summer at a given time. Tropical monsoons are most typical and persistent in the northern part of the Indian Ocean basin. This is largely facilitated by the seasonal change in the atmospheric pressure regime over the Asian continent. The fundamental features of the climate of this region are associated with the South Asian monsoons.

The formation of tropical monsoons in other regions of the globe is less characteristic when one of them, the winter or summer monsoon, is more clearly expressed. Such monsoons are observed in Tropical Africa, in northern Australia and in the equatorial regions of South America.

Earth's constant winds - trade winds And westerly winds- depend on the position of atmospheric pressure belts. Since low pressure prevails in the equatorial belt, and near 30 ° N. sh. and yu. sh. - high, near the surface of the Earth throughout the year the winds blow from the thirtieth latitudes to the equator. These are trade winds. Under the influence of the rotation of the Earth around its axis, the trade winds deviate to the west in the Northern Hemisphere and blow from the northeast to the southwest, and in the Southern they are directed from the southeast to the northwest.

From the high pressure belts (25-30°N and S), the winds blow not only towards the equator, but also towards the poles, since at 65°N. sh. and yu. sh. low pressure prevails. However, due to the rotation of the Earth, they gradually deviate to the east and create air currents moving from west to east. Therefore, westerly winds prevail in temperate latitudes.

Interestingly, the idea of ​​"non-flying weather" for passengers and pilots can sometimes be very different. What is “heavy fog” for a passenger may turn out to be “a veil over which a bright sun shines” for a pilot. And in the same way, what is “normal weather” for the passenger, for the pilot “the inability to land the plane at the destination due to strong crosswinds and icing on the runway.”

"Non-flying weather" is not just a natural phenomenon, like a downpour, heavy snowfall or fog.

This term refers to several factors, such as:

Technical parameters of the aircraft,

Technical equipment and condition of a particular airport,

pilot training,

direct weather conditions.

The technical parameters of an aircraft are the data set by the manufacturer, under which the safe operation of the aircraft is possible. That is, for example, if the airport is well equipped and can handle flights in heavy fog, and a particular aircraft is not equipped with sufficiently modern navigation devices for landing in very low visibility conditions, then the flight cannot be operated. Since a 100% successful landing cannot be guaranteed, and this poses a threat to passengers and crew. Roughly speaking, the aircraft on instruments may "not see" the runway.

Maldives Airport is a single runway on an island in the open ocean.

Runway at Hulule Airport, Maldives

There are airfields equipped with the latest technical innovations, and they can receive flights in conditions of almost zero visibility. And there are airports where the minimum visibility should be, for example, 600 or 800m. And even if the aircraft is equipped with the latest technology, in conditions of poor visibility, the flight to this airport cannot be operated.

When performing any flight, of course, the professional training of pilots is taken into account. It is not enough that the aircraft be "the latest model with all the technical innovations." It would be nice if the pilots knew how to use these same innovations and had supporting documents. Then, "and we will fly away into the fog, and we will sit down in the rain."

Well, the most interesting - weather.

By weather conditions, we passengers, as a rule, mean heavy rain or snowfall, strong wind, hail, lightning, fog.

For pilots, three factors are decisive:

- runway condition,

- visibility,

- wind.

Runway condition- this is both the state of the strip itself, and the consequences of weather conditions on this strip, such as icing or heavy snowfall, which can negate all the work of cleaning the strip. Under such conditions, takeoff and landing may be impossible.

Visibility is affected fog, rain, snow, dust, smoke, in general, everything that lowers this very visibility. And it is not so important what exactly caused the poor visibility. The main thing is how well the runway is visible in specific conditions.

Here it is still necessary to clarify such a moment as the height of the decision, or, as they say, the point of no return - this is the height to which, when descending, the pilot can still go around. That is, before this altitude, the pilot must decide whether he can land or is forced to climb again.

Wind is a very important factor, influencing the decision "to take off or not to take off". Side wind can be a danger, because to compensate for it you have to turn the plane a little into the wind. And when landing, at the moment of adhesion to the runway, the aircraft must be turned sharply and directed along the axis of the landing line, which can be difficult to do.

The direction of the wind is also of great importance. Planes take off and land against the wind. This reduces the takeoff and run distance, that is, it allows you to take off earlier during takeoff or reduce the speed of the aircraft faster during landing.

But there are airports where it is impossible to change the direction of takeoff / landing due to geographical features. For example, on one side of the runway the sea, on the other - the mountains. If the wind blows towards the sea, then it is possible to land (towards the mountains), but it is no longer possible to take off (a tailwind does not make it possible to quickly get off the ground). Therefore, it is sometimes not clear to passengers why some planes fly (that is, they land), while others do not (that is, they do not take off).

There is one more nuance in the question “to fly or not to fly”. All flights are conditionally divided into 2 categories: flight duration up to 2 hours and more than 2 hours. In the first case (for short distances), pilots are allowed to rely on the actual weather and ignore the forecast. In the second option (long distances), they are guided, first of all, by the forecast, and only then they look at the actual weather at the airfield.

The final decision on takeoff and landing is always made by the aircraft commander.

And if he decides not to fly, trust me, it's for your own good.

Don't blame the airline, or the pilots, or the airport, but thank everyone for your life.

Travel safely!

And have a good rest!