In the weather forecast issued by the Meteorological Observatory, we often hear that the wind turns from north to south, and the wind force is 2 to 3. The "level" here represents the wind speed.
Wind speed is the forward speed of the wind. The greater the air pressure difference between two adjacent places, the faster the air flow, the greater the wind speed and the greater the wind force. Therefore, the magnitude of wind is usually expressed by wind power. The unit of wind speed is meters per second or kilometers per hour. When releasing the weather forecast, most of them use the wind level.
How to determine the series of wind power?
/kloc-More than 0/000 years ago, in the Tang Dynasty in China, people recorded weather phenomena such as sunny, rainy and snowy weather, and measured the wind. At the beginning of the Tang dynasty, an accurate instrument for measuring wind speed was not invented, but at that time, the moving speed of wind could be calculated according to the characteristics of wind to objects, and the wind grade could be determined. There is such a record in Li's "Phenomenon Play Zhan": "The moving leaves are ten miles, the songs are hundred miles, the branches are two hundred miles, the leaves are three hundred miles, the dead branches are four hundred miles, the big branches are five hundred miles, the stones are three thousand miles." This is to estimate the wind speed according to the influence of wind on trees. "moving leaves for ten miles" means that the leaves are slightly fluttering and the wind speed is ten miles a day; What "sings" is the rustling of leaves, and the wind speed at this time is hundreds of miles a day. In addition, some wind grades are determined according to the symptoms of trees, such as "first-class moving leaves, second-class ringing, third-class shaking branches, fourth-class falling leaves, fifth-class broken branches, sixth-class broken branches, seventh-class broken trees, flying sand and stones, and eighth-class uprooting". These eight winds, plus "no wind" and "gentle wind" (when the wind comes, it is cool and gentle, so it is called gentle wind), which can be combined into ten levels. The grades of these winds are not much different from those imported from abroad. This can be said to be the earliest wind level in the world.
More than 200 years ago, there were no instruments for measuring the magnitude of wind, and there were no unified regulations. Every country expresses itself in its own way. At that time, there was a man named beaufort in England. He carefully observed the situation of various objects on land and at sea in different winds, and accumulated 50 years of experience before he classified the wind into 13 in 1805. Later, after research and supplement, the original explanation was explained more clearly, and the speed of each wind level was improved, which became the "jargon" for forecasting wind power now. In some places, the content of the wind level is compiled into songs for memory:
Zero-level windless cooking smoke; The first-class soft wind smoke is slightly inclined;
The leaves of the second breeze ring; Three-level breeze swaying branches;
Level 4 gale dust; Five-level breeze waves;
Six-level strong wind shakes trees; Seven winds are difficult to walk;
The branches of the eight-strong wind are broken; Nine-level gale chimney was destroyed;
Ten-level gale uprooting; Eleven storm lands are rare;
12 hurricane has terrible waves.
The distance that the wind moves per second-the wind speed, its formula is "from all the way to nine, multiplied by two". It means: from 1 to 9 winds, multiply each level by 2, and you can roughly get the maximum wind speed. For example, the maximum speed of the first wind is 2 meters per second, the second wind is 4 meters per second, the third wind is 6 meters per second, and so on. There are also transitional figures between different levels of wind, such as the first level wind 1-2 meters per second, the second level wind 2-4 meters per second, the third level wind 4-6 meters per second and so on. Here is a wind scale.
wind scale
Smooth wave height (m) Equivalent wind speed (m/s) of sea surface and fishing boat mark land surface object mark
Median value of general highest range *
0- Calm still smoke rises 0.0 ~ 0.20.
1 0. 1 0. 1 Microwave smoke can indicate the wind direction, and the leaves slightly shake by 0.3 ~ 1.5 1.
2 0.2 0.3 There were small ripples, fishing boats shook people's faces to feel the wind, leaves made a slight noise, flags began to flutter, and tall grass and crops began to shake 1.6 ~ 3.32.
There was a small wave on 3 0.6 1.0, and the fishing boat gradually felt the leaves and twigs shaking, the flag unfurled, and the tall grass and crops shaking for 3.4 ~ 5.44.
4 1.0 1.5 There are some white foams on the crest. When the fishing boat is full of sails, it can make the hull lean to one side, blow up the dust and paper on the ground, shake the branches, and the tall grass and crops fluctuate by 5.5 ~ 7.97.
5 2.0 2.5 There is more white foam on the wave peak, some leaves and twigs of fishing boats swing, there are waves on the inland water surface, and the waves of tall grass and crops fluctuate obviously by 8.0 ~ 10.79.
63. 04. 0 The white foam began to be blown off the peak by the strong wind, and most branches of the fishing boat were broken by the earthquake, and the wires whizzed, making it difficult to hold up the umbrella. Tall grass and crops fall to the ground from time to time.
7 4.0 5.5 White foam leaves the peak and is blown into stripes. The whole tree shakes and the branches bend, making it inconvenient to walk in the wind13.9 ~17.16.
8 5.5 7.5 The white foam was blown into obvious stripes and broke twigs. When going against the wind, people felt great resistance, ranging from 17.2 to 20.7 19.
9 7.0 10.0 The horizontal visibility is reduced due to the waves blown by the wind, and the straw house is damaged due to the navigation difficulty of the motorized sailboat, and the roof tiles are lifted, and the branches can be broken by 20.8 ~ 24.4 23.
10 9.0 12.5 The waves from the wind obviously reduce the horizontal visibility, and the motorboat navigation is quite dangerous. Trees can be blown down, and general buildings are damaged by 24.5 ~ 28.426.
111.516.0 The waves from the wind obviously reduce the horizontal visibility, and the extremely dangerous trees encountered by motorboats can be blown away, and the general buildings are seriously damaged by 28.5 ~ 32.6 3 1.
1214.0-sea waves are rare on land and extremely destructive >; 32.6 >3 1
In fact, in nature, the wind sometimes exceeds 12. For example, the central wind force of a strong typhoon or tornado may be much larger than the magnitude of 12, but the wind above the magnitude of 12 is rare, so the magnitude is generally not specified.
In order to measure the wind more accurately, people often use portable anemometers to measure the wind in the field. This kind of portable anemometer generally consists of an induction part and a counter (see the left picture). The induction part consists of three air cups (there are also four air cups) installed on the cross. The air cups can rotate freely on bearings and are protected by a small frame. The lower part of the central shaft is connected with the counter, and when the air cup rotates, the counter also rotates. So the counter records the number of revolutions of the air cup. A counter usually has two or three counters, with the large pointer indicating single digits and ten digits, and the pointers on the two small counters indicating hundred digits and single digits respectively. There is a switch (starting lever) at the lower part of the instrument. Pushing up can make the counter engage with the sensing part, and the counter starts to work. When the starting lever is pulled down, the counter is separated from the sensing part and stops working. When the instrument is placed in a high place and it is not convenient to start it directly by hand, you can connect the switch with a small rope. When observing, you can pull the rope to open and close. Portable anemometers are generally placed in open areas around without tall obstacles, and their bodies are vertical. Turn off the switch before observation and write down the instructions of the pointer. After a minute or two, turn on the switch and start the stopwatch to record the time. At this point, the observer quickly left the anemometer and stood downwind of the instrument. After starting the instrument for nearly 100 seconds, the observer quickly approaches the instrument, turns off the switch at 100 seconds, and records the indication of the second hand. According to the two readings before and after, calculate the difference value, indicating the scale number of anemometer pointer during the observation time, and record it in the record table. Divide this difference by the observation time, and you can get the scale number of anemometer per second, and take one decimal place. Then, according to the number of scales per second, the average wind speed (unit: m/s) is found from the anemometer verification certificate, and one decimal place is taken.
It is best to observe it twice in a row and take its average value to eliminate the instrument itself and human error.
Some portable anemometers have not only the structural performance of the anemometer mentioned above, but also a wind vane on the shaft to indicate the wind direction. This kind of anemometer is called anemometer.