Why does it rain when a typhoon blows?
Because typhoons are tropical cyclones, so-called cyclones, that is, low pressure. The so-called low pressure means that the central air pressure is low, so the central air rises. As the altitude rises, the temperature drops, and the water vapor turns into rain and falls down.
Typhoon is a huge rising cloud, and its airflow is rising. Typhoon brings huge water vapor from the ocean. Due to the action of updraft, it meets the hot air mass above the ground, and the temperature of water vapor decreases, thus causing rainfall.
Judging from the typhoon structure, such a behemoth must have unique conditions.
First of all, there must be a vast atmosphere with high temperature and high humidity. The temperature and humidity of the bottom atmosphere on the tropical ocean surface are mainly determined by the sea surface temperature, and typhoons can only form on the warm ocean surface where the sea surface temperature is higher than 26℃-27℃ and the sea surface temperature is higher than 26℃-27℃ within 60 meters.
Second, there should be an initial disturbance in which the lower atmosphere converges to the center and the upper atmosphere spreads outward. Moreover, the divergence of the upper layer must exceed the convergence of the lower layer in order to maintain enough updraft and continuously strengthen the disturbance of the lower layer;
3. The difference of vertical wind speed should not be too big, and the relative motion of the upper and lower air is very small, so that the latent heat released by water vapor condensation in the initial disturbance can be stored in the air column in the typhoon eye area, forming and strengthening the typhoon warm center structure;
Fourth, there must be enough geostrophic deflection, and the earth's rotation is conducive to the formation of cyclonic vortices. The geostrophic deflection force is close to zero near the equator and increases at the north and south poles. Typhoons basically occur on the ocean surface about 5 latitudes from the equator.
What is a typhoon danger semicircle?
A mature typhoon can be divided into three parts from the center to the periphery.
One is the central eye area.
This is the central part of the typhoon, the wind is light and the waves are small, and sometimes there will be a clear sky Wan Li;
The second is the vortex region.
Close to the eye of the typhoon, the wind and rain in this area are the most intense and destructive;
The third is the peripheral area.
This is the outermost layer of the typhoon, and the wind speed in this area is also very high, but it is not as violent as the vortex area.
Due to the uneven distribution of air pressure around the typhoon, the distribution in the strong wind area is also uneven.
Generally speaking, the side near the high pressure has large wind speed, wide range and high waves, which is easy to cause shipwrecks; On the contrary, the wind speed near the low pressure is small, the wind area is narrow and the waves are low.
Therefore, when the typhoon moves from east to west (or northwest), because the right side of the typhoon direction is adjacent to the western Pacific subtropical high, the right hemisphere of the typhoon is usually stronger and the left hemisphere is weaker. So the right semicircle of typhoon is called "dangerous semicircle" and the left semicircle is called "navigable semicircle".
What secondary disasters will rainstorm cause?
The heavy rain caused many disasters. First of all, rainwater flows into the river, and the river can't bear it, so there will be floods.
In addition, landslides are prone to occur in complex terrain. If the soil is loose and there are some deposits, it is easy to produce mudslides. In the plateau area, the snow below is washed away, which is easy to cause landslides, avalanches and other disasters.
Among the secondary disasters caused by rainstorm, there are forest fires and grassland fires that have great influence on modern society. For example, most natural fires in Australia and the United States a while ago were caused by lightning.
Lightning itself sometimes hurts people, but the probability of a city being struck by lightning is very small. Because there are many tall buildings in the city with lightning rods on them, lightning strikes will be attracted first, so people are safer.
But in the wild, such as thunderstorm weather, it will be more dangerous to cross the overpass on the expressway. Because people are the tallest around, and many overpasses are made of metal, they are very vulnerable to lightning strikes, so in this environment, you should stay away from empty places or lower your body.
In addition, lightning strikes are also very harmful to electrical appliances, such as various household appliances and some equipment in the computer room. Therefore, usually any large project needs lightning protection facilities and can only be put into use after acceptance.