What is the concept of wind grade?

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

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 strong wind, the twigs of trees can be broken, and people walk against 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.

Winds above 12 are called typhoons or hurricanes, which are extremely destructive and rarely seen on land.

Extended data:

Wind grade measurement method:

In order to measure the wind more accurately, people often use portable anemometers to measure the wind in the field. This portable anemometer generally consists of a sensing part and a counter. 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. 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.

References:

Baidu Encyclopedia-Level of Wind