Typhoon knowledge

Typhoon is actually a strong tropical cyclone. Tropical cyclone is a strong weather system that occurs in tropical ocean. Like a vortex moving forward in a flowing river, it rotates rapidly around the center and moves forward with the surrounding atmosphere. In tropical cyclones in the northern hemisphere, the airflow rotates counterclockwise around the center, while in the southern hemisphere, it is the opposite. The closer to the tropical cyclone center, the lower the air pressure and the stronger the wind. However, tropical cyclones with strong development, such as typhoons, have a calm and clear sky area at their center, that is, the typhoon eye.

The intensity of tropical cyclones occurring in tropical oceans varies greatly. When the maximum wind force near the center of tropical cyclone is less than 8, it is called tropical depression; Tropical storms are called winds of 8 or 9. Strong tropical storms with winds of 10 and 1 1; Only tropical cyclones with maximum wind force 12 near the center are called typhoons.

The generation and development of tropical cyclones need huge energy, so they are formed on the tropical ocean surface with suitable meteorological conditions such as high temperature and high humidity. According to statistics, tropical cyclones are generated in tropical oceans all over the world except the South Atlantic.

Tropical cyclone disaster is the most serious natural disaster, because its frequency is much higher than that of earthquake disaster, so its cumulative loss is also higher than that of earthquake disaster. 1991The tropical cyclone that landed in Bangladesh at the end of April claimed139,000 lives. China is one of the countries suffering from the most tropical cyclones in the world. In recent years, its average annual loss is more than 100 billion yuan, and the loss caused by a strong tropical cyclone like typhoon 94 17 is more than 100 billion yuan.

2. What is the typhoon path?

Looking down from space, the typhoon looks like a spinning top, and the trajectory of the spire of this virtual top is the typhoon path. Throughout the history of typhoons, the paths of typhoons are various, and there has never been a typhoon with the same path.

There are many reasons for the typhoon path, mainly because the typhoon is affected by complex atmospheric environment and other factors in the process of atmospheric movement. If the atmospheric environment is a big palette, then the newly generated typhoon is like a canvas. When it is painted with different colors by the atmosphere in motion, it will produce different paths. At present, typhoons affecting China are mainly generated in the western Pacific, and the common paths are:

Move west. After the typhoon was generated from the east of the Philippines, the basic airflow around it was very weak. At this time, the movement of typhoon center is mainly internal force movement, and the direction is northwest. Due to the influence of the subtropical high at high altitude, the deep easterly airflow will guide the typhoon to move westward. Typhoons moving along this path have the greatest impact on the coastal areas of Hainan, Guangdong and Guangxi, mostly in spring and autumn.

Northwest moving path. After the typhoon is generated in the eastern Philippines, it will encounter southerly winds with the axis from northwest to southeast. Under the guidance of this deep airflow, the typhoon will move from the east of the Philippines to the northwest, land in Taiwan Province Province via bashi channel, and then cross the Taiwan Province Strait to approach the eastern part of Guangdong or the coastal areas of Fujian, and land in Taiwan Province, Fujian, Guangdong and other coastal areas. If the starting latitude of the typhoon is high, it will pass through the Ryukyu Islands, land in the coastal areas of Zhejiang, Shanghai and Jiangsu, and even reach Shandong and Liaoning. Typhoons moving along this path have the greatest impact on Taiwan Province Province, eastern Guangdong Province and Fujian Province, and such typhoons mostly appear in late July to early September.

Turning path. The typhoon generated from the east of the Philippines and moved to the northwest. When it is blocked by the western Pacific subtropical high or the offshore westerly trough, it will turn northeast and move to the Korean Peninsula or Japan. This turning typhoon can be divided into three categories: turning eastward, transiting and turning westward. Among them, the typhoon that turns west, especially after landing in China's coastal areas, turns to the northeast, and its path is parabolic, which is also the most common path. The typhoon moving along this path has the greatest impact on the eastern coastal areas of China. Most of these typhoons occur in summer and autumn, but the latitude of the turning point changes with the seasons, with the northernmost part being summer and the southernmost part being spring.

Special path. When the environment of typhoon changes rapidly, or there are multiple typhoons interacting at sea, the moving path of typhoon will become very strange, just like the gyro is affected by external force when it rotates, and the center will move in a cyclone arc. When this movement is just opposite to the original movement direction, it will lead to the stagnation and rotation of the typhoon. If the external force is unbalanced, it will swing from side to side, like a moving snake. Such a moving path is more complicated and more difficult to predict, so it is more prone to disasters. For example, Typhoon Lily (200 1) has a special moving path. After it was formed, it slowly turned around the northern waters of Taiwan Province Province, landed near Yilan, Taiwan Province Province, and rushed to the Taiwan Province Strait after 44 hours of raging, and finally landed again in Chaoyang and Huilai, bringing serious disasters and huge losses to the local area. Typhoon "Lily" lasted 14 days, strengthened into a typhoon three times and weakened into a tropical storm three times, and its peculiar path left a deep impression on people.

China's meteorological departments attach great importance to the monitoring of typhoons, and the moving path of typhoons is the focus of monitoring. In the era of underdeveloped science and technology, it is impossible to monitor the generation and movement of typhoons because of the large ocean area, and typhoons are often not discovered until they approach ships and land. In the 1960s, after meteorological satellites were put into operation, every typhoon, especially its moving path, could not escape the eyes of the satellites. Since then, the meteorological department has never missed the news of a typhoon.

Advanced satellite remote sensing technology has provided great help for typhoon observation and forecast. Starting from 1980, meteorological departments can basically make correct typhoon forecasts for typhoons landing in China. With the development of satellite remote sensing, radar detection and numerical forecasting technology, the level of typhoon monitoring and forecasting can be reached to a higher level, and the typhoon track is in people's hands.