Beijing Weather Beijing Meteorological Observatory

Level 7 is called gale, which can make trees shake, and it will be difficult to walk in the wind on the road. Huge waves can be set off on the sea, and coastal fishing boats stop in the harbor and anchor overseas.

Wind power refers to the strength of the wind when it blows on an object. According to various phenomena generated when the wind blows on objects on the ground or on the water, the wind force can be divided into 18, with the minimum being 0 and the maximum being 17.

The size of the wind depends on the wind speed, that 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.

As early as 1000 years ago, in the Tang Dynasty, the wind was measured. In addition to recording weather phenomena such as rain and snow, the ancients also measured wind power.

Although the instrument for measuring wind speed was not invented in the Tang Dynasty, at that time, according to the performance of wind on objects, the moving speed of wind was also calculated and the wind level was estimated.

Li's "Phenomenon Drama" records this way:

Move leaves for 10 miles, sing for 100 miles, shake branches for 200 miles, leave leaves for 300 miles, break branches for 400 miles, break big branches for 500 miles, walk stones for 1000 miles and pull out big roots for 3000 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; "Singing a hundred miles" means that leaves rustle and the speed of the wind is one hundred miles a day.

In Yi Si Zhan, trees are also graded according to their performance.

"First-level moving leaves, second-level voice, third-level shaking branches, fourth-level falling leaves, fifth-level folding branches, sixth-level folding big branches, seventh-level folding wood, flying sand, and eighth-level pulling up big trees and roots". This can be said to be the earliest wind level in the world.

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

Level 0 wind is also called no wind. Smoke straight

1 Soft wind smoke can indicate the wind direction.

The leaves blowing in the breeze make a slight sound.

Leaves and branches are swaying in the breeze.

The wind rises, dust and scraps of paper rise, and twigs shake.

The twigs shook in the breeze, and there were small waves on the water.

6 Strong wind, branches shaking, wires whirring.

The strong wind shook the whole tree, making it difficult to walk against the wind.

The branches broke in the strong wind, which had great resistance to the wind.

The strong wind caused minor building damage.

10 gale some trees were pulled up and buildings were seriously damaged.

1 1 storms are rarely encountered, accompanied by extensive damage.

12 hurricane has great destructive power and is rare on land.