In meteorology, the wind is generally divided into twelve classes according to the size of the wind:

Class 0 wind is also called no wind.

Level 2 winds are called light winds, where leaves are slightly audible and the human face feels windy.

Level 4 winds are called gentle winds, in which the twigs of the trees shake and can blow up dust and paper on the ground.

6 winds are called strong winds, with large branches shaking, wires whistling and umbrellas making it difficult to walk.

Force 8 winds are called gale force winds, which can break the thin branches of trees and make it difficult for people to walk against the wind.

10 winds are called gales, which are rare on land and can uproot trees and cause serious damage to buildings.

Winds above 12 are called typhoons or hurricanes, and are rare on land because of their destructive power.

There are many types of winds, depending on the size and direction of the wind and the humidity. Gale, gale, gale, gale, storm and hurricane, these common types of winds, the Beaufort wind level wind force of seven, eight, nine, ten, eleven and twelve, respectively.

Wind force is the magnitude of the force exhibited by wind blowing on an object. Generally based on the various phenomena produced by the wind blowing on objects on the ground or water, the size of the wind force is divided into 18 levels, the smallest is 0, the largest is 17.

Wind speed is the forward speed of the wind. The greater the difference in air pressure between two neighboring places, the faster the air flows, the greater the wind speed, the force of the wind is naturally greater. So it is usually wind power to indicate the size of the wind. The unit of wind speed is expressed in meters per second or kilometers per hour. And most of the time when weather forecasts are issued, the wind force rating is used.

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Expanded information:

Wind is a natural phenomenon on the Earth, which is caused by radiant heat from the sun. The sun's rays shine on the Earth's surface, causing the surface temperature to rise, and the air on the surface is heated and lightened by expansion and rises. After the hot air rises, cold air with low temperature flows horizontally, and the rising air gradually cools and becomes heavy and falls, because the surface temperature is high and will heat the air to make it rise, this air flow produces the wind.

Collected water vapor (cloud) into water, the volume shrinks, the surrounding water vapor to replenish, the formation of wind. Wind on Earth is related to the source of water, and wind is produced by the expansion and contraction of water and water vapor. The wind blows from the sea to the land, or the land to the sea.

In the summer on the ground at high temperatures, air, water vapor expansion rise, to the sea surface than the air, water vapor to supplement the ground air space, the sea surface temperature is low air contraction. To be high temperature on the ground by the air, water vapor expansion rise of air, water vapor to replenish the sea surface air space. In the winter sea surface temperature high sea surface air rise, the ground temperature low air specific weight along the ground to supplement the sea surface space.

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