What is the wind speed of 4 meters per second?
Wind power refers to the strength of the wind blowing on an object. Generally speaking, according to various phenomena caused by wind blowing on objects on the ground or water surface, the magnitude of wind power is divided into 18, with the smallest being 0 and the largest being 17.
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 the weather forecast is released, the wind level is mostly used.
In the Tang Dynasty more than 1000 years ago, our people not only recorded weather phenomena such as rain and snow, but also 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 trees". 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 divided the wind into 13 in 1805, which is also commonly known as Beaufort wind scale. Later, after research and supplement, the original explanation was explained more clearly, and the speed of each wind level was increased, which became the "jargon" for forecasting wind power.
Reference: Wind Speed-Baidu Encyclopedia