How to monitor a typhoon that “runs” throughout its life?

Recently, this year's fifth super typhoon "Dusurui" has had a serious impact on my country. Subsequently, this year's sixth typhoon "Kano" formed in the northwest Pacific Ocean first gradually approached the coast of Zhejiang and Fujian, but suddenly "turned sharply" to the northeast; then the generated "Lane" turned from the northwest to the northwest; "Dora" moved into the northwest Pacific Ocean...

When faced with the typhoons that keep appearing on the screen, children may also wonder: How do typhoons form and disappear? Why do typhoons "run"? Why can the "running" path change at any time? How are typhoon paths monitored? When children ask questions, it is the best opportunity for us to infiltrate scientific education.

What is a typhoon

A typhoon is a tropical cyclone that usually forms over tropical oceans. When the sea temperature exceeds 26 degrees Celsius, water vapor on the sea surface rises to form clouds, which gradually rotate to form a low-pressure area. As the water vapor continues to rise and condense, the center of the typhoon gradually forms, accompanied by strong storms and heavy rains.

Depending on the different geographical locations and different sea areas where they are formed, tropical cyclones generated in the western Pacific are called "typhoons"; those generated in the Atlantic and eastern Pacific are called "hurricanes"; and those born in the South Pacific and Indian Oceans are called "cyclones."

A typhoon has strong convective activity and strong cyclonic circulation, and can only be called a typhoon if the central wind force exceeds level 12. Typhoons are divided into six levels according to the maximum average wind force (wind speed) near the bottom center: tropical depression, tropical storm, severe tropical storm, typhoon, severe typhoon and super typhoon.

When a typhoon moves from tropical areas to land or low-temperature sea areas, it loses heat and water vapor replenishment, its energy source is cut off, and the typhoon will gradually weaken and then disappear.

Where do typhoons get their names from?

Why is "Dusurui" named? What does "Kano" mean? In fact, before 1995, typhoons did not have a unified name. It was not until 1997 that the World Meteorological Organization decided to use Asian-style names for typhoons in the northwest Pacific and the South China Sea.

After the meeting, 14 members, including Cambodia, China, North Korea, Hong Kong, China, Macau, China, Japan, Laos, Malaysia, Federated States of Micronesia, Philippines, South Korea, Thailand, the United States and Vietnam, each provided 10 names for typhoons. Then, the 140 names were drawn into a table and used year after year. For example, the name "Dusuri" was provided by South Korea and refers to a bird of prey. It has been used for the third time; the name "Kanu" was provided by Thailand and means jackfruit and has been used four times.

Once a typhoon causes particularly heavy damage to life and property, its name will be deleted from the naming list, such as "Longwang", "Mangkhut", "Haiyan" and "Molandi". The vacant typhoon name caused by the removal of the name will be replaced by a new name proposed by the typhoon committee of the corresponding nominating country or region.

What will the typhoon bring?

Typhoons often bring strong winds, heavy rains and storm surges, which bring disasters to humans as well as benefits. During their formation and movement, typhoons bring fresh water resources to humans, alleviating water shortages.

In the western Pacific region, the path and speed of a typhoon have a significant impact on people's lives and property. If a typhoon moves quickly, it may cause a concentrated outbreak of extreme weather phenomena such as heavy rain and strong winds in a short period of time, causing great damage to people's lives and property. If a typhoon moves slowly, it may cause prolonged rainfall and strong winds, increasing the risk of disasters such as floods and landslides.

For this reason, typhoon path is one of the most concerned issues in typhoon weather analysis and forecasting, and requires enhanced monitoring.

How do typhoon paths change?

The typhoon path is guided by the environmental flow field of the entire troposphere. From the equator to 25° north latitude, the typhoon moves from east to west due to the influence of the westward blowing of the trade winds. Due to the influence of the Coriolis effect (right deviation), the typhoon is guided to the mid-latitudes; when the typhoon moves northward to the mid-latitudes, due to the influence of the prevailing westerly winds, the movement path may change from west to east.

Therefore, the path of a typhoon rotating clockwise in the Northern Hemisphere in the Northwest Pacific usually moves westward, northwestward, and northeastward. Similarly, from the equator to 25° south latitude, due to the Coriolis effect (left deviation) and the trade winds blowing tropical cyclones westward, the path of a hurricane rotating counterclockwise in the Southern Hemisphere in the South Pacific usually moves westward, southwestward, and southeastward.

Because the Coriolis effect in the equatorial region is zero, there are no tropical cyclones near the equator. The sea areas within 5° north and south latitudes cannot rotate to form typhoons because the Coriolis effect is too weak.

How to monitor the path of a typhoon

The path of a typhoon is complex and changeable. The high or low pressure encountered during the movement will adjust the typhoon path. Strong winds at high levels may cause latent heat diffusion, which may also change the development and movement path of the typhoon. For example, on August 4, "Kano" suddenly got "stuck" and then made a "sharp turn" to the northeast. Starting on the 7th, the typhoon path moved northwards to the southwestern waters of Japan, which was due to the combined influence of the Pacific subtropical high pressure and other pressure fields.

Modern geographic information technology plays an important role in typhoon monitoring, prediction and response. Using multiple data sources such as satellite remote sensing, meteorological observations and numerical models, combined with geographic information system technology, typhoon paths can be predicted and analyzed, providing a scientific basis for typhoon response.

(The first author is a teacher at Dongyuan Middle School in Heyuan City, Guangdong Province, and a student at Luo Mingjun's famous teacher studio in Guangdong Province. The second author is a teacher at Lin Qien Memorial Middle School in Lufeng City, Guangdong Province, and a student at Luo Mingjun's famous teacher studio in Guangdong Province)