Why do typhoons often land in Wenzhou?

Typhoon is a powerful and deep tropical cyclone formed in the tropical ocean. Typhoon classification The National Meteorological Administration of China stipulates that the international tropical cyclone name and grade standard shall be used from 1989 1 month. According to international standards, the maximum average wind force near the center of tropical cyclone is less than 8, which is called tropical depression, 8 ~ 9 is called tropical storm,10 ~1is called strong tropical storm, and1is called typhoon. In order to issue typhoon warnings uniformly, the typhoons that appear in the west of150 E and on the northern surface of the equator every year are numbered in the order of appearance. For example, Typhoon 9202 means that this typhoon is the second typhoon west of 1992. Typhoon activity is seasonal. The typhoons that affect China mainly occur from May to 10, especially from July to September. The source of the typhoon is the 22222222 area. Typhoon sources are distributed on the ocean surface with islands near 5 north latitude and 20 south latitude. Typhoons affecting China are mainly formed in the western Pacific Ocean to the east of the Philippines, near Guam and in the middle of the South China Sea. Typhoon structure and weather A mature typhoon is divided into three parts according to its structure and weather: typhoon eye, vortex storm area and peripheral gale area, which are arranged concentrically from the center to the outside. The typhoon eye is located in the center of the typhoon, with a diameter of about 5 ~ 10 km. Downward flow prevails at the eye of the typhoon, so the weather is clear and windless. Outside the eye of the typhoon is a vortex wind and rain area, where strong convergent updraft prevails, forming thick clouds, and violent storms occur from time to time. The wind force is often above 12, which is the worst weather area for typhoons. Further outward is the peripheral windy area, and the wind speed decreases outward, and the wind force is generally above 6. Typhoon crossing often brings stormy weather, causing huge waves on the sea surface and seriously threatening navigation safety. After landing, it can destroy crops and various building facilities. It has caused great losses to people's lives and property and is a disastrous weather with great harm. The formation of typhoon must meet the following conditions: ① A vast ocean with high temperature. The formation and development of typhoons need huge energy, which mainly comes from the latent heat released by a large amount of water vapor condensation. On the surface of tropical ocean, seawater has high temperature and strong evaporation, and a large amount of heat and water vapor are transported into the atmosphere through turbulent motion, which has unstable conditions of high temperature and high humidity, and a large amount of internal energy is a huge energy source for typhoon generation and development. ② Suitable flow field. Appropriate circulation conditions can start and induce high temperature and high humidity air to generate disturbance, so that the airflow convergence will rise. ③ Proper geostrophic deflection. After the airflow moves, there must be a certain steering force. If the geostrophic deflection force does not reach a certain value, the airflow gathered at the center will reach the low-pressure center, so that cyclone vortex cannot be formed and typhoon cannot be formed. So typhoons usually occur between 5 degrees and 20 degrees north latitude. ④ The vertical shear of wind should be small. Under the action of geostrophic bias, the convergent updraft develops into a cyclonic vortex. The air flow rises, adiabatic cooling produces condensation, and the latent heat released by condensation heats the air. The vertical shear of the wind becomes smaller, so that the latent heat does not spread outward, maintaining the warm core structure of the typhoon. The feedback from the warm heart makes the air pressure in the center of the typhoon drop continuously, and the air vortex becomes stronger and stronger, which eventually develops into a typhoon. The movement of the typhoon will move after the typhoon is formed. The moving path basically moves from east to west along the outer edge of subtropical high. However, influenced by many factors, the moving path is very complicated. Take the typhoon movement path in the western part of the North Pacific as an example, its path is divided into three: ① westward movement path. The typhoon moved westward from the eastern Philippines, crossed the South China Sea and landed in Hainan Island or Vietnam. ② Northwest path. The typhoon moved from the east of the Philippines to the northwest, crossed the Ryukyu Islands and landed in Jiangsu, Zhejiang and Fujian provinces. ③ Turning path. The typhoon moved from the east of the Philippines to the northwest, then turned to the northeast, and its path was parabolic. As for why there are so many typhoons in Wenzhou, it is of course a matter of geographical location!