How is the wind graded?

The classification of wind power has both magnitude and direction, so the wind forecast includes wind speed and direction. The magnitude of wind speed is often expressed by several winds. The level of wind is determined according to the degree of influence of wind on ground objects. In meteorology, at present, it is generally divided into twelve grades according to the magnitude of wind. Level 0 wind is also called no wind. Level 2 wind is called breeze, the leaves are slightly noisy, and people feel windy. Level 4 wind is called breeze, and the twigs of trees shake, which can blow up dust and paper on the ground. The 6-level wind is called strong wind, the branches are shaking, the wires are whistling, and it is difficult to walk with an umbrella. The 8-level wind is called gale, the twigs of trees can be broken, and people walk in the wind with great resistance. 10 wind is called gale, which is rare on land. Trees can be pulled up and buildings are seriously damaged. /kloc-winds above 0/2 are called hurricanes, which have great destructive power and are rare on land. In the weather forecast, we often hear the expression "the north wind is 4 to 5", in which the wind refers to the average wind; If you hear the phrase "gust 7", gust refers to the wind with high and low speed, and the wind at this time refers to the high-speed wind.