The Beaufort scale is an empirical measure of wind strength, based mainly on observations of the state of the sea and the waves on its surface. Currently, it is the standard for assessing wind speed and its impact on terrestrial and marine objects around the world. Consider this issue in more detail in the article.
A Brief Biography of Francis Beaufort
The creator of the wind power rating scale, Francis Beaufort, was born in 1774. From an early age, he began to show interest in the sea and ships. Having entered the Royal Navy of Great Britain, he directed all his efforts to building a career for a sailor. As a result, Beaufort was able to achieve the rank of Admiral of the Royal Navy.
During his service, he not only performed naval tasks, but also devoted much time to compiling geographic maps and making observations in various corners of the planet. Beaufort served even in old age. He died in 1857, when he was 83 years old.
The first scale for estimating wind speed
Beaufort scale was proposed in 1805. Up to this point, there was no specific standard according to which it would be possible to assess how weak or strong the wind blows. Many sailors based on their subjective ideas.
Initially, the wind force on the Beaufort scale was presented in the form of a calibration from 0 to 12. Moreover, each point did not speak about the speed of air mass movement, but about how to behave in terms of controlling the ship. For example, when you can set sail, and when they need to be removed to avoid breaking the masts. That is, the original Beaufort wind scale pursued exclusively practical goals in the maritime industry.
This scale was adopted as a standard for the British fleet only in the late 1830s.
Land scale application
Beginning in the 1850s, the Beaufort scale began to be used for land purposes. A mathematical formula was developed to translate its points into the physical quantities used to measure wind speed, that is, in meters per second (m / s) and kilometers per second (km / s). In addition, manufactured anemometers (instruments that measure wind speed) also began to calibrate based on this scale.
At the beginning of the 20th century, meteorologist George Simpson added to the scale the effects that a corresponding-strength wind produced on land. Starting in the 1920s, the scale began to be widely used throughout the world to describe phenomena associated with wind power, both at sea and on land.
The relationship between scale points and wind power
As already noted above, the wind power in points on the Beaufort scale can be converted into units that are convenient for use. To do this, use the following formula: v = 0.837 * B 1.5 m / s, where v is the wind speed in meters per second, B is the value of the score on the Beaufort scale. For example, for 4 points of the considered scale, which corresponds to the name "moderate breeze", the wind speed will be: v = 0.837 * 4 1.5 = 6.7 m / s or 24.1 km / h.
It is often necessary to obtain the velocity of air masses in kilometers per hour. For this purpose, one more mathematical relationship between the points of the scale and the corresponding physical quantity was derived. The formula is: v = 3 * B 1.5 ± B, here v is the speed with which the wind blows, expressed in km / h. Note that the “±” mark allows you to get the speed limits that correspond to the specified score. So, in the example above, the wind speed on the Beaufort scale, which corresponds to 4 points, will be equal to: v = 3 * 4 1.5 ± 4 = 24 ± 4 km / h or 20-28 km / h.
As can be seen from the example, both formulas give the same result, therefore, can be used to determine wind speed in certain units.
Further in the article we will describe the consequences of the impact of wind of one or another force on various natural objects and human structures. To this end, the entire Beaufort scale can be divided into three parts: 0-4 points, 5-8 points and 9-12 points.
Scores from 0 to 4
If the anemometer shows that the wind is within 4 points of the scale under consideration, then they speak of a light breeze:
- Calm (0): the surface of the sea is smooth, without waves; smoke from a bonfire rises vertically.
- Light breeze (1): small waves without foam at sea; smoke indicates the direction the wind is blowing.
- Weak breeze (2): transparent crests of waves that are continuous; leaves from the trees begin to fall and the blades of the windmills move.
- Light breeze (3): small waves, their crests begin to break; leaves on trees and flags begin to fluctuate.
- Moderate breeze (4): many “lamb” on the surface of the sea; paper and dust rise from the ground, the crowns of the trees begin to flutter.
Scores from 5 to 8
These Beaufort wind scores cause the breeze to turn into strong winds. The following description corresponds to them:
- Fresh breeze (5): waves at sea of medium size and length; slight wobble of tree trunks, the appearance of ripples on the surface of lakes.
- Strong breeze (6): large waves begin to form, their crests break apart, and sea foam forms; tree branches begin to swing, difficulties arise in holding an open umbrella.
- Strong wind (7): the surface of the sea becomes extremely wavy and “voluminous”, foam is carried away by the wind; large trees start to move, difficulties arise when pedestrians move against the wind.
- Strong wind (8): large waves that “break”, the appearance of strips of foam; the crowns of some trees begin to break, pedestrian traffic is hindered, some vehicles move under the influence of wind.
Scores from 9 to 12
The last Beaufort score marks the onset of a storm and a hurricane. The consequences of such winds are given below:
- Very strong wind (9): very large waves with broken crests, visibility decreases; damage to trees, the impossibility of normal movement of pedestrians and vehicles, some artificial structures begin to be damaged.
- Storm (10): thick waves, on the crests of which foam is visible, the color of the surface of the sea turns white; trees uproots, damage to buildings.
- Severe storm (11): very large waves, the sea is completely white, visibility is very low; destruction of a different nature everywhere, heavy rain, floods, the flight of people and other objects in the air.
- Hurricane (12): huge waves, white sea and zero visibility; flight of people, vehicles, trees and parts of houses, widespread destruction, wind speed reaches 120 km / h.
Hurricane Scales
Naturally, the question arises: are there winds that blow stronger than 120 km / h on our Earth? In other words, is there a scale that describes the different strengths of hurricanes? The answer to this question is positive: yes, such a scale exists, and it is not the only one.
First of all, it should be said that the Beaufort hurricane scale also exists, and it simply fits in with the standard scale (points from 13 to 17 are added). This extended scale was developed back in the middle of the last century, however, although it can be used to describe tropical hurricanes that often occur on the coasts of Southeast Asia (Taiwan, China), it is rarely used. For these purposes, there are other special scales.
A detailed description of the hurricanes is given in the Saffir-Simpson scale. It was developed in 1969 by an American engineer Herbert Saffir, then Simpson added flood-related effects to it. This scale divides all hurricanes into 5 levels depending on wind speed. It covers all possible limits of this value: from 120 km / h to 250 km / h and more, and describes in detail the destruction typical for a given point. The Saffir-Simpson scale is easy to translate into an extended Beaufort scale. So, 1 point for the first will correspond to 13 points of the second, 2 points - 14 points and so on.
Other theoretical tools for classifying hurricanes are the Fujita scale and the TORRO scale. Both scales are used to describe a tornado or tornado (type of hurricane), while the first is based on the classification of damage from a tornado, the second has a corresponding mathematical expression and is based on the speed of the wind in the tornado. Both scales are used throughout the world to describe this type of hurricane.