How are tsunamis and typhoons formed?

Reason:

Tsunami is a powerful and destructive wave. When there is an earthquake on the seabed, the sea water fluctuates violently due to the power of seismic waves, forming powerful waves, moving forward and flooding coastal areas one by one. This is the so-called tsunami.

Prevention and control:

Earthquakes can trigger tsunamis, so how can the earthquake monitoring system provide tsunami warning letters? In earthquake-prone areas around the world, such as the Pacific coast and the Indian Ocean coast, there should be a perfect earthquake monitoring network.

Danger:

Soon after the violent vibration, the huge waves roared, crossed the coastline, crossed the fields and violently attacked the cities and villages on the shore. In an instant, people disappeared in the waves. All the facilities and collapsed buildings in the port were swept away by the rough waves. Afterwards, the beach was a mess, full of broken wood and human and animal bodies. The disasters brought by earthquakes and tsunamis to human beings are enormous. At present, human beings can only prevent or reduce the losses caused by sudden disasters such as earthquakes, volcanoes and tsunamis through prediction and observation, but they cannot control their occurrence.

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* Typhoon *

Reason:

The cause of typhoon is uncertain, but it is known that it developed from the disturbance of tropical atmosphere. In the tropical ocean, the sea surface is exposed to direct sunlight, which makes the temperature of seawater rise, and the seawater is easy to evaporate into water vapor and spread in the air. Therefore, the air in the tropical ocean has high temperature and high humidity, and this air expands due to high temperature, resulting in the decrease of density and weight. The wind near the equator is weak, easy to rise, and convection occurs. At the same time, the surrounding cold air flows in to replenish and then rises again. This cycle will eventually make the temperature of the whole air column higher and the mass lower. Air flows from high pressure to low pressure, just as water flows from high pressure to low pressure, air with higher ambient pressure will flow to low pressure, thus forming "wind". In summer, due to the direct sunlight moving from the equator to the north, the southeast trade winds in the southern hemisphere cross the equator and become southwest monsoon to invade the northern hemisphere. When they meet the northeast trade wind in the northern hemisphere, the air is forced to rise, thus increasing the convection. Due to the different directions of southwest monsoon and northeast trade wind, when they meet, they often cause fluctuations and vortices. The convergence caused by the southwest monsoon and the northeast trade wind and the continuation of the original convection make the vortex with low pressure continue to deepen, that is, the air around it accelerates to flow to the center of the vortex, and the faster the flow, the greater the wind speed; When the maximum wind speed near the ground reaches or exceeds17.2m per second, we call it a typhoon.

Prevention and control:

Strengthening the monitoring and forecasting of typhoons is an important measure to reduce typhoon disasters. Meteorological satellites are mainly used to detect typhoons. The existence and size of the typhoon can be clearly seen on the satellite cloud picture. Using meteorological satellite data, we can determine the location of typhoon center, estimate the intensity of typhoon, monitor the direction and speed of typhoon movement, and the area where severe storms occur, which plays a key role in preventing and mitigating typhoon disasters. When the typhoon reaches the offshore, the radar can also detect it. There are also forecasters of meteorological stations, who, based on all kinds of information obtained, analyze the trend of typhoons, the place and time of landing, issue typhoon forecasts, typhoon emergency reports or emergency warnings in time, serve the public through television, radio and other media, and provide decision-making basis for governments at all levels. Issuing typhoon forecast or emergency report is an important measure to reduce typhoon disaster.

Danger:

Typhoon is a very destructive and disastrous weather system, but sometimes it can also play a beneficial role in eliminating drought. Its harmfulness mainly includes three aspects:

(1) Strong wind. The maximum wind force near the typhoon center is generally above 8.

② Heavy rain. Typhoon is one of the strongest rainstorm weather systems. Generally, it can produce rainfall of150 mm ~ 1 000 mm in the area where typhoons pass, and a few typhoons can produce heavy rain above1000 mm. The torrential rain caused by Typhoon No.3 in the upper reaches of Huaihe River 1975 created the extreme value of heavy rain in Chinese mainland and caused the "75.8" flood in Henan.

③ Storm surge. Generally, typhoons will increase water in coastal waters, and the maximum water increase in coastal areas of Jiangsu Province can reach 3m. Typhoon "9608" and "97 1 1" increased water, which made Jiangsu's coastal areas along the Yangtze River have a super-historical climax.