Beaufort's wind level depends on the influence of wind on smoke, dust, ground objects, fishing boats and fishing waves. It is often used to estimate wind speed. Wind power is divided into 0- 12 and * *13 according to its strength, which is currently recommended by the World Meteorological Organization. Usually, in the weather forecast, "Dongfeng level 3" and other expressions refer to "Beaufort level".
In the 1950' s, the progress of wind measuring instruments made it possible to measure the wind in nature greatly beyond 12, so the wind level was expanded to 17, that is, * * *18. However, the classification adopted in the Maritime Meteorological Service Manual of the World Meteorological Organization is only 0 to 12, and the extended classification from 13 to 17 is not recommended.
Extended data
The cause of wind
Wind is a kind of air flow phenomenon on the earth, which is generally caused by solar radiation heat. Sunlight shines on the earth's surface, causing the surface temperature to rise, and the surface air to expand and become lighter and lighter. After the hot air rises, the cold air with low temperature flows in horizontally, and the rising air falls down because it gradually cools and becomes heavier. Because the surface temperature is high, it will heat the air and make it rise. This airflow is the wind.
When the gathered steam forms water, its volume shrinks, and the surrounding steam comes to replenish it, forming wind. The wind on the earth is related to the water source, and the wind is produced by the expansion and contraction of water and steam.
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