Information about typhoons

Typhoon is a strong tropical cyclone generated on the surface of tropical ocean. Typhoons are often accompanied by strong winds and heavy rains. The wind rotates counterclockwise. Isobars and isotherms are approximately a set of concentric circles. The central air pressure is the lowest and the temperature is the highest.

Typhoon classification. Typhoons are classified according to the maximum wind force near the center of tropical cyclones. In the past, the meteorological department of our country called the winds with the magnitude of 8 to 1 1 as typhoons, and the winds with the magnitude of 12 or above as strong typhoons. From 65438+65438+ 1 in 0989 to 65438+1in October, it is called a tropical storm when the maximum wind force near the center is 8 ~ 9, and it is called a strong tropical storm when10 ~1. For the sake of simplicity, the following is still collectively referred to as typhoon.

Typhoon path. Typhoon paths can be roughly divided into three categories: ① Westward typhoons move from the east to the west of the Philippines, cross the South China Sea, and finally land on Hainan Island in China or northern Vietnam. (2) Landing type: The typhoon moved to the northwest, crossed the Taiwan Province Strait, landed in the coastal areas of Guangdong, Fujian and Zhejiang, and gradually weakened into a low pressure. This typhoon has the greatest impact on China. The two typhoons "90 15" and "97 1 1" which have had the greatest impact on Jiangsu in recent years belong to this type. (3) Parabolic type: The typhoon moves to the northwest first, then turns to the northeast when approaching the eastern coast of China, and turns to the vicinity of Japan, with a parabolic path. Typhoon disaster. Typhoon is a very destructive and disastrous weather system, but sometimes it can also play a beneficial role in eliminating drought. Its harmfulness mainly includes three aspects: ① strong wind. The maximum wind force near the typhoon center is generally above 8. ② Heavy rain. Typhoon is one of the strongest rainstorm weather systems. Generally, it can produce rainfall of150 mm ~ 1 000 mm in the area where typhoons pass, and a few typhoons can produce heavy rain above1000 mm. The torrential rain caused by Typhoon No.3 in the upper reaches of Huaihe River 1975 created the extreme value of heavy rain in Chinese mainland and caused the "75.8" flood in Henan. ③ Storm surge. Generally, typhoons will increase water in coastal waters, and the maximum water increase in coastal areas of Jiangsu Province can reach 3m. Typhoon "9608" and "97 1 1" increased water, which made Jiangsu's coastal areas along the Yangtze River have a super-historical climax.

After the typhoon is formed, it will generally move out of the source and experience the evolution process of development, weakening and extinction. A mature typhoon has a circular vortex radius of 5 OOKM ~ 1000 km and a height of 15 km ~ 20 km. Typhoon consists of three parts: peripheral area, maximum wind speed area and typhoon eye. The wind speed in the peripheral area increases from outside to inside, with spiral clouds and precipitation; The strongest precipitation occurs in the maximum wind speed area, with an average width of 8 km ~ 19 km, and there is a circular cloud wall between it and the typhoon eye; The typhoon eye is located in the center of the typhoon. The most common typhoon eye is round or oval, ranging in diameter from 10 km to 70 km, with an average of about 45km. The weather in typhoon eye is calm, partly cloudy, dry and warm.

Typhoon number. China numbered the tropical depressions that entered the west of l50 degrees east longitude and the north of l0 degrees north latitude. The winds near the center were strong and reached magnitude 8, which were arranged in the order of annual occurrence. This is the "Typhoon X this year (tropical storm, strong tropical storm)" that we heard or saw on radio and television.

Danger:

Typhoon has brought abundant rainfall to vast areas and become a rainfall system closely related to human life and production. However, typhoons always bring all kinds of injuries. Because of its sudden and destructive power, it is one of the most serious natural disasters in the world.

The destructive power of typhoons is mainly caused by strong winds, heavy rains and storm surges.

1. Strong typhoon is a huge energy pool, and its wind speed is above 17m/s, even above 60m/s ... According to the measurement, when the wind reaches 12, the wind pressure per square meter on the plane perpendicular to the wind direction can reach 230kg.

2. Rainstorm typhoon is a strong precipitation system. When the typhoon lands, the rainstorm center can drop 100-300mm a day, or even reach 500-800mm. The floods caused by typhoons and rainstorms are the most dangerous disasters. Typhoon rainstorm is strong, flood occurs frequently, spreads widely, and is fierce and destructive.

3. Storm Surge The so-called storm surge means that when the typhoon moves to the land, due to the typhoon's strong wind and low air pressure, the sea water accumulates strongly in the direction of the coast, the tide level rises sharply, and water waves are overwhelming to the coast. The storm surge of a strong typhoon can raise the coastal water level by 5-6 meters. Storm surge meets astronomical high tide level, resulting in high-frequency tide level, which leads to tidal overflow, seawall burst, washed away houses and various building facilities, flooded towns and farmland, and caused a large number of casualties and property losses. Storm surge will also cause coastal erosion and land salinization caused by seawater intrusion.

Prevention:

Before the typhoon comes, we should pay attention to watching the typhoon disaster weather warning information released by meteorological stations at all levels. In order to ensure the safety of primary and secondary school students, we should make corresponding preparations in advance, minimize going out, stay away from low-lying areas and dangerous areas such as the seaside, and stay away from dangerous facilities or articles such as trees and billboards. Move schools, students and residents in dangerous areas to safe areas in advance.

The meaning of typhoon blue warning signal: it may be affected by tropical cyclones within 24 hours, with an average wind force of more than 6 or a gust of more than 7; Or have been affected by tropical cyclones, the average wind force is 6 ~ 7, or the gust is 7 ~ 8 and may continue.

The yellow warning signal of typhoon means: it may be affected by tropical cyclones within 24 hours, with an average wind force of more than 8 or a gust of more than 9; Or it has been affected by tropical cyclones, with an average wind force of 8 ~ 9, or a gust of 9 ~ 10 and may continue.

The meaning of the orange warning signal of typhoon: it may be affected by tropical cyclones within 12 hours, and the average wind force may reach 10 or above, or the gust 1 1 above; Or have been affected by tropical cyclones, the average wind force 10 ~ 1 1, or the gust1/kloc-0 ~/2 may continue. The meaning of typhoon red warning signal: It may or may have been affected by tropical cyclones within 6 hours, and the average wind force may reach or reach 12 or above and may continue.