Traditional Culture Encyclopedia - Weather forecast - How does a typhoon form, what are its characteristics, and what are its hazards or impacts?
How does a typhoon form, what are its characteristics, and what are its hazards or impacts?
A typhoon (or hurricane) is a severe tropical cyclone that occurs on the tropical ocean. It's just that the name is different depending on where it happens. Tropical cyclones that occur in the western North Pacific, west of the International Date Line, including the South China Sea, are called "typhoons"; while tropical cyclones that occur in the Atlantic Ocean or the eastern North Pacific are called "hurricanes." In other words, typhoons are called "hurricanes" in Europe and North America, "typhoons" in East and Southeast Asia, "cyclonic storms" in the Bay of Bengal, and "cyclones" in the Southern Hemisphere.
The passing of typhoons is often accompanied by strong convective weather such as strong winds and heavy rain or extremely heavy rain. Wind direction rotates counterclockwise in the Northern Hemisphere (clockwise in the Southern Hemisphere). On a weather map, the isobars and isotherms of a typhoon are approximately a set of concentric circles. The central air pressure and temperature reach their lowest values, and the weather conditions are extremely severe, but the weather is usually calm near the eye of the typhoon.
The typhoon with the highest intensity and the lowest pressure near the center in history is Super Typhoon Taipei (TIP).
The formation of typhoons
The direct sunlight on the tropical sea surface increases the temperature of the sea water. The sea water evaporates into water vapor and rises into the sky. The surrounding cooler air flows in to replenish it and then rises again. The circulation will eventually cause the entire air flow to continue to expand and form "wind". Due to the vastness of the sea surface, the air circulation continues to increase in diameter to several kilometers. Because the earth rotates at a high speed from west to east, friction occurs between the airflow column and the earth's surface. The closer to the equator, the stronger the friction force, which causes the airflow column to rotate counterclockwise (the southern hemisphere rotates clockwise). Due to the rapid rotation of the earth, The airflow column cannot keep up with the speed of the earth's rotation and appears to move westward, which forms what we now call typhoons and their paths. The center of the typhoon is located in the T-shaped position of the wind direction we see currently. It is not difficult to judge the distance and direction of the typhoon center based on the wind direction and speed. Based on my 40 years of observing the direction of the clouds before typhoon approaching, I can basically determine whether the typhoon is passing through the local area, and it is basically accurate. The accuracy of local forecasts has been exceeded many times. When the maximum wind speed near the ground reaches or exceeds 17.2 meters per second, we call it a typhoon.
(The following is the description of the first volume of the geography book for high school students published by the People's Education Press)
In tropical or subtropical oceans where the ocean surface temperature exceeds 26°C, due to the near-ocean surface temperature High, a large amount of air expands and rises, reducing the air pressure near the ocean surface, and the peripheral air continuously flows in and rises. Affected by the geostrophic deflection force, the inflowing air rotates. As the rising air expands and cools, the water vapor in it cools and condenses to form water droplets, which releases heat and causes the lower air to continue to rise. In this way, the air pressure near the ocean surface drops even lower, the air rotates more violently, and finally a typhoon is formed.
Typhoon structure Typhoon structure From the typhoon structure, we can see that such a huge behemoth must have unique conditions for its production.
1. There must be a broad atmosphere of high temperature and high humidity. The temperature and humidity of the bottom atmosphere on the tropical ocean are mainly determined by the sea surface water temperature. Typhoons can only form on warm ocean surfaces where the sea temperature is higher than 26°C-27°C, and the seawater temperature within 60 meters is higher than 26°C. ℃-27℃;
2. There must be an initial disturbance in which the lower atmosphere converges toward the center and the upper atmosphere diffuses outward. Moreover, high-level divergence must exceed low-level convergence to maintain sufficient updraft and low-level disturbances to continue to strengthen;
3. The wind speed in the vertical direction cannot differ too much, and the relative movement of the upper and lower air is very small. The latent heat energy released by the condensation of water vapor in the initial disturbance is concentrated and stored in the air column in the typhoon eye area, forming and strengthening the typhoon warm center structure;
4. There must be a large enough geostrophic deflection force for the earth to The rotation is conducive to the generation of cyclonic vortices. The geostrophic deflection force is close to zero near the equator and increases toward the north and south poles. Typhoons basically occur on the ocean surface about 5 latitudes or more from the equator.
[Edit this paragraph] The origin of typhoons
The origins of typhoons are distributed in the vast low-latitude ocean of the northwest Pacific. The initial location of tropical disturbances in the northwest Pacific that intensify and develop into typhoons has relatively concentrated areas in both longitude and latitude. In the east-west direction, tropical disturbances develop into typhoons relatively concentrated in four sea areas:
(1) South China Sea area;
(2) East of the Philippine Islands, Ryukyu Islands, and Guam and other nearby sea surfaces (the most important typhoon origin);
(3) The sea surface near the Mariana Islands;
(4) The sea surface near the Marshall Islands.
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