Knowledge about typhoons
1． What is a typhoon?
Typhoons are actually severe tropical cyclones. A tropical cyclone is an intense weather system that occurs in the tropical ocean. It is like a vortex advancing in a flowing river, rotating rapidly around its center while moving forward with the surrounding atmosphere. The airflow in a tropical cyclone rotates counterclockwise around the center in the Northern Hemisphere, and vice versa in the Southern Hemisphere. The closer you get to the center of a tropical cyclone, the lower the air pressure and the stronger the wind. However, when a tropical cyclone develops strongly, such as a typhoon, its center is an area of calm clear sky, which is the eye of the typhoon.
Tropical cyclones that occur over tropical oceans vary widely in intensity. When the maximum wind force near the center of a tropical cyclone is less than level 8, it is called a tropical depression; when the wind force is level 8 and 9, it is called a tropical storm; when the wind force is level 10 and 11, it is a severe tropical storm; only when the maximum wind force near the center reaches level 12, it is called a tropical cyclone. called a typhoon.
The generation and development of tropical cyclones require huge amounts of energy, so they form on the tropical ocean surface where high temperature, high humidity and other suitable meteorological conditions exist. According to statistics, tropical cyclones are generated in all tropical oceans around the world except the South Atlantic.
Tropical cyclone disasters are the most serious natural disasters. Because their occurrence frequency is much higher than that of earthquake disasters, their cumulative losses are also higher than that of earthquake disasters. The tropical cyclone that made landfall in Bangladesh at the end of April 1991 claimed 139,000 lives. Our country is one of the countries most affected by tropical cyclones in the world. In recent years, the average annual losses caused by them have been more than 10 billion yuan. A landfalling strong tropical cyclone like Typhoon No. 9417 has caused more than 10 billion yuan in losses at a time. Yuan Yuan.
2. What is a typhoon track?
Looking down from space, a typhoon looks like a spinning top. The trajectory of the tip of this virtual top during its movement is the path of the typhoon. Throughout the history of typhoons, typhoon paths have been diverse, and there has never been a typhoon with the same path.
The reasons for the variety of typhoon paths are mainly that typhoons are affected by factors such as the complex atmospheric environment during the atmospheric movement. If the atmospheric environment is like a big color palette, the newly generated typhoon is like a canvas, which is painted with different colors by the atmosphere during its movement, resulting in different paths. The typhoons currently affecting our country are mainly born in the Western Pacific. Their common paths are:
Westward path. After a typhoon forms from the ocean east of the Philippines, the basic airflow around it is very weak. At this time, the movement of the typhoon center is mainly due to internal force movement, heading northwest. Due to the influence of the high-altitude subtropical high, the deep easterly airflow will guide the typhoon to move westward. Typhoons that move along this path until they land on the western coast of Guangdong, Hainan Island or Vietnam have the greatest impact on the coastal areas of Hainan, Guangdong and Guangxi in my country, often occurring in spring and autumn.
Northwest path. After a typhoon forms in the eastern waters of the Philippines, it will encounter a southerly wind with an axis from northwest to southeast. Under the guidance of this deep airflow, the typhoon moves northwest from the ocean east of the Philippines, lands in Taiwan through the Bashi Strait, and then passes through Taiwan. The strait approaches the eastern part of Guangdong or the coast of Fujian, and makes landfall along the coasts of Taiwan, Fujian, and Guangdong. If the typhoon starts at a higher latitude, it will pass through the Ryukyu Islands, land on the coasts of Zhejiang, Shanghai, and Jiangsu in my country, and even reach Shandong and Liaoning. Typhoons moving along this path have the greatest impact on my country's Taiwan Province, eastern Guangdong Province and Fujian Province. Such typhoons are more common from the second half of July to the first half of September.
Turn path. A typhoon originates from the ocean east of the Philippines and moves northwest. When it encounters the obstruction of the western Pacific subtropical high or westerly trough at sea, it turns northeast and moves towards the Korean Peninsula or Japan. This kind of turning typhoon can be divided into three categories: east turning, medium turning and west turning. Among them, the west-turning type, especially the typhoons that turn westward when they reach the offshore areas, turn to the northeast after landing in the coastal areas of my country, and the path is parabolic, which is also the most common path. Typhoons moving along this path have the greatest impact on my country's eastern coastal areas. Such typhoons mostly occur in summer and autumn. However, the latitude of the turning point varies with the season. It is in the far north in midsummer and in the far south in spring.
Special path. When the environmental situation of a typhoon changes rapidly, or when there are multiple typhoons interacting with each other at sea, the moving path of the typhoon will become weird. It is like a top being affected by external forces when rotating, and the center will make a cyclonic pattern. circular motion. When this movement is exactly opposite to the direction of the original movement, it will cause the typhoon to stagnate and spin. If the external force it receives is unbalanced, it will sway from side to side, like a moving snake. Such movement paths are complex and difficult to predict, making them more likely to cause disasters. For example, the movement path of Typhoon "Lily" that occurred in 2001 was a special path. After it was generated, it was like a snake that slowly circled in place in the northern sea of Taiwan and then landed near Yilan, Taiwan. It raged for 44 hours and then moved to the Taiwan Strait, and finally made landfall again in Chaoyang and Huilai, bringing serious disasters and great losses to the local areas. Typhoon "Lily" lasted for 14 days, intensifying into a typhoon three times and weakening into a tropical storm three times. Its weird path left a deep impression on people.
my country’s meteorological department attaches great importance to typhoon monitoring, and the movement path of typhoons is the focus of monitoring.
In an era when science and technology was underdeveloped, due to the large scope of the ocean, it was impossible to monitor the formation and movement of typhoons. The existence of typhoons was often not discovered until they approached ships and land. In the 1960s, after meteorological satellites were put into operational use, the occurrence and development of every typhoon, especially its movement path, could not escape the eyes of satellites. Since then, the meteorological department has not missed any detection or report. News of a typhoon.
Advanced satellite remote sensing technology has provided great help in the observation and forecasting of typhoons. Since 1980, the meteorological department has basically been able to make correct typhoon forecasts for typhoons that have made landfall in my country. With the development of satellite remote sensing, radar detection and numerical forecasting technology, the level of typhoon monitoring and forecasting will be improved to a higher level, and the path of typhoons will be within people's control.