It develops from disturbances in the tropical atmosphere. In tropical oceans, the temperature of the seawater rises due to direct sunlight on the sea surface, and the seawater easily evaporates into water vapor and spreads in the air. Therefore, the air in the tropical ocean has high temperature and high humidity. This air expands due to the high temperature, causing the density to decrease. Small, the mass is reduced, and the wind near the equator is weak, so it is easy to rise and convection occurs. At the same time, the surrounding cooler air flows in to supplement it, and then rises again. This cycle continues, and eventually the entire air column will be higher in temperature and heavier. Lighter, less dense air, which forms what is called a "tropical depression." However, the flow of air is from high pressure to low pressure, just like water flowing from high to low. The air in the surrounding areas with higher pressure must flow to the lower pressure, forming "wind". In summer, because the direct sunlight area moves northward from the equator, the southeast trade winds in the southern hemisphere cross the equator and turn into southwest monsoons to invade the northern hemisphere. They meet the original northeast trade winds in the northern hemisphere, forcing the air to rise and increasing convection. The southwest monsoon and the northeast trade wind have different directions, and their encounter often causes fluctuations and vortices. This convergence caused by the encounter between the southwest monsoon and the northeast trade wind continues with the original convection, making the vortex that has formed into a low pressure continue to deepen, that is, the surrounding air flows faster toward the center of the vortex. , the greater the wind speed; when the maximum wind speed near the ground reaches or exceeds 17.2 meters per second, we call it a typhoon.
From the structure of typhoons, we can see that there must be unique conditions for the production of such a huge behemoth.
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