Disaster of typhoons
Typhoon storm surges occur mostly in summer and autumn when typhoons are at their peak with the characteristics of fierce, fast, strong and destructive, which can occur in all coastal areas affected by typhoons; temperate storm surges occur mostly in spring and autumn, and also in summer, generally, the process of increasing water is relatively gentle, and the height of increasing water is lower than that of typhoon storm surges, middle latitude coastal areas often occur, especially along the coasts of the North Sea of Europe, the East Coast of the United States and the northern coast of China.
The Northwest Pacific Ocean is the most suitable region for typhoon generation in the world, accounting for 36% of the total frequency of typhoon generation. China is one of the countries most attacked by typhoons, according to the statistics of the past 50 years, about 7 to 8 typhoons landed in China every year. According to statistics from 1988 to 2004, the annual economic losses caused by typhoons in the mainland of China are 23.35 billion yuan, 440 deaths, 307,000 collapsed houses and 288.5*104 hm2 affected areas of crops.
China has a large latitude span, and parts of southern China often suffer from tropical cyclone disasters with high frequency and large losses.The frequency of tropical cyclones in China is rare in the world.The global average annual occurrence of tropical cyclones with maximum wind force of 8 or more near 80 centers, of which 28, or about 35%, occur in the Northwest Pacific Ocean.On average, about 7 Tropical Cyclones Landed on the coastal areas of China every year.On August 2, 1922, a strong typhoon storm surge hit Shantou area, causing a huge storm surge disaster, more than 70,000 people were killed and countless people were displaced, this was a storm surge disaster with the largest number of deaths in China since the 20th century,at that time, the intensity of typhoon exceeded 12 levels, resulting in an increase of water up to 3.5m.In some years, Tropical Cyclones Landed continuously in a very short period of time, which caused great difficulties in defense work.No. 0414 (Yunna)landed in Wenling, Zhejiang province on August 12, 2004,which was the strongest typhoon landing in Zhejiang in 48 years and the strongest typhoon landing in the mainland of China in 8 years.
Affected by typhoon "Yunna", heavy rainstorms fell in Zhejiang, Fujian, Jiangxi, Anhui, Henan, Hubei and Hunan provinces,parts of were torrential rain or the rainstorm, while effectively alleviating drought and increasing water storage in rivers and reservoirs, precipitation also had a serious impact on Zhejiang and other provinces, a total of 18 million people were affected, 184 people died, 9 people were missing, and more than 700,000hm crops were affected, the direct economic loss was more than 20 billion yuan.
The strongest tropical cyclone recorded in history was typhoon Tipper, which occurred in the Northwest Pacific October 12,1979.The estimated sustained wind speed at the center was 85m/s.The maximum rainfall caused by tropical cyclone occurred from 7 to 8 January 1966, and the rainfall of tropical cyclone Dennis was 1144 mm within 12 hours.The most deadly tropical cyclone was the Bangladesh Cyclone in 1970, which killed at least 300,000 people.The most devastating tropical cyclone was Hurricane Andrew in 1992, which hit the Bahamas, Florida and other places in the United States, causing property losses of up to 26.5 billion dollars.
Benefits of typhoons
Typhoons not only bring severe disasters such as storms to landing areas, but also have certain benefits.For some areas, if there are no typhoons, there will be no crop growth and agricultural harvest in these areas.Typhoons can sometimes play a beneficial role in relieving drought.In addition, typhoons play an important role in regulating the earth's heat and maintaining the heat balance. Scientific research has found that the benefits of typhoons to human beings are as follows:
(1) With the rapid increase of global population and the development of industry and agriculture, the demand for freshwater is expanding day by day, in addition, the limited freshwater resources on land are unevenly distributed, and the worldwide water shortage has become more and more serious.Typhoon, a tropical cyclone, has brought plenty of fresh water to people.Typhoons bring a large amount of rainwater to the coastal areas of China, Japan, India, Southeast Asia and southeastern United States, accounting for more than a quarter of the total precipitation in these areas, which has a great significance to improve freshwater supply and ecological environment in these areas.
(2) The tropical and subtropical regions near the equator have the longest sunshine time and the most unbearable dry and hot weather, if there is no typhoon to dissipate the heat in these areas, which will be hotter there and the sandy desert on the surface will be more serious.Meanwhile, the cold zone will be colder and the temperate zone will disappear. There will be no spring city like Kunming in our country, nor Guangzhou, which is evergreen all the year round, the "Beidacang" and Inner Mongolia grassland will no longer exist.
(3) The maximum speed of a typhoon can reach more than 200 km per hour, the energy is equivalent to the energy emitted by 400 hydrogen bombs of 2000t class when they explode, wherever they go, they have unbreakable power.This huge energy can directly cause disasters to human beings, but it also relies on the huge energy flow to keep the earth in thermal balance, so that human beings can live and work in peace and contentment.
(4) During the formation and operation of typhoons with enormous energy, the long chain of water molecules can be broken by lightning and other functions, and the short chain of water molecules with activity can be formed.After inhaling these short-chain water molecules, the organisms on the earth can increase the vitality of life and make the earth's ecology develop continuously.
(5) Typhoons can also increase fishing production. Whenever a typhoon hits, which turns the river upside down, rolls up the nutrients at the bottom of the river and sea, increases bait, attracts fish to gather near the water surface, and naturally increases catches.
Prevention of typhoons
Strengthening the monitoring and forecasting of typhoons is an important measure to mitigate the typhoon disaster.The detection of typhoons is mainly uses meteorological satellites.The presence and size of typhoons can be seen clearly in satellite images.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 areas where storms occur, which play a key role in preventing and mitigating typhoon disasters.When the typhoon reaches the offshore, radar can also be used to monitor the trend of the typhoon.In addition, the forecasters of the meteorological station analyze the trend, landing place and time of typhoons according to various data obtained, issue typhoon forecast, typhoon warning or emergency warning in time, serve the public through TV, radio and other media, and provide decision-making basis for governments at all levels at the same time.Publishing typhoon forecast or warning is an important measure to mitigate typhoon disasters.
Today, with the rapid development of science and technology, modern equipment has been able to accurately predict the specific movement direction, landing point and time of the wind.As long as we take effective defensive measures, improve the level of scientific detection and early warning, do well in prevention, resistance and rescue, and seek advantages and avoid disadvantages, we can minimize the degree of disaster.
Early warning signals of typhoons
Early warning signals of typhoons are divided into four levels, which are expressed in blue, yellow, orange and red respectively, shown in table 6-5.
Table 6-5 Early warning signals and preventive guidelines of typhoon disaster
[Preventive measures] Before typhoon arrives, it is necessary to transfer to safety zone in time to avoid the above places which are easy to cause casualties, never take shelter from the wind and rain.
Timely reinforcement of high-altitude objects
Strong winds can blow down high-altitude objects, which can easily cause injury and death.Such as balconies, roof pots, air conditioning outdoor units, awnings, solar water heaters, roof sundries, sporadic items, tools, building materials on construction sites are easily blown down by the wind, causing casualties.
[Preventive measures]To fix pots and other items in time, construction enterprises should arrange and stack construction equipment, tools and sporadic materials to ensure safety.
Walking away from rivers, lakes and sea bridges
Doors, windows and curtain wall glasses are easily broken by strong wind, causing glass splashing to kill and injure people; pedestrians are blown down in the water or on the road, bridge and water edge, and are killed, injured or drowned;wires are blown off by the wind, causing pedestrian casualties; ships at sea (inland) are capsized and sink by the wind and waves, and vehicles on the highway, especially on the highway, are blown over causing casualties.
[Preventive measures] Before typhoon comes, pedestrians should take shelter from wind and rain in a safe place in time and avoid walking on embankments and bridges near rivers, lakes and seas as far as possible, as long as ships return to harbour in time to take shelter and anchor, people on board must take shelter from wind and vehicles must avoid driving in areas affected by strong winds.
How to avoid a typhoon at sea? What about ships at sea before a typhoon arrives?
(1) Before typhoon approaching, the ship should obey the command and take shelter in the shelter immediately.
(2)If it is too late to escape or encounter a typhoon, it is necessary to contact the relevant departments on shore in time for rescue.
(3) When waiting for rescue, we should take the initiative to take emergency measures and take prompt and decisive measures to leave the typhoon, such as stopping (stagnating), deviating (going around), passing (passing thorough quickly).
(4)Soon after the strong typhoon, the wind and waves are calm, maybe when the eye of the typhoon passes by, at this time, the owner of the port must not go back to reinforce the ship in order to protect his property.
(5)When conditions permit, the ship shall be equipped with beacon machines, radio communication machines, satellite telephones and other modern equipment.
(6) In the absence of radio communication equipment, when passing ships or aircraft are found, or close to land, objects can be used to send out easily detectable distress signals in time, such as stacking “SOS”, setting off fireworks, sending out light and sound signals, shaking colorful objects, etc.
How to avoid a typhoon?
When a ship sailing at sea encounters a typhoon, the avoidance method is usually adopted to avoid being involved in the storm area in the center or periphery of the typhoon.Ships can change their course and speed according to the dynamics and intensity of typhoon, so that they can keep a certain distance from the center of typhoon, and be outside the range of strong wind which the ship can resist.
The wind direction of the right half circle of typhoon is close to the moving route of typhoon, the wind speed of the right half circle is larger than that of the left half circle, and most typhoons turn to the right, which makes it easy to roll ships into the center of typhoon in the right half circle,therefore, the right half circle of typhoon is called “dangerous half circle” and the left half circle is called “navigable half circle” at sea.
When a ship encounters a typhoon at sea, it should locate itself according to the typhoon's condition and dynamic forecast, as well as the changes of wind, wind direction and air pressure observed on the spot, so as to take appropriate navigation methods and stay away from the typhoon center as soon as possible.The methods for judging the ship's position and the navigation measures to be taken are as follows:
(1) The wind direction changes clockwise, the pressure drops continuously, and the wind force increases gradually; at this time, the ship position is in the front half of the dangerous semi-circle of typhoon, that is, the dangerous quadrant, and should sail at full speed with the starboard overhead wind at the bow.
(2) The wind direction changes counter-clockwise, the pressure drops continuously, and the wind force increases gradually, at this time, the ship position is in the front half of the navigable semi-circle of the typhoon, and it should sail at full speed with the starboard stern under the wind.
(3) The wind direction remains unchanged, the pressure drops continuously, and the wind force increases gradually; at this time, the ship is on the way of typhoon, and should sail at full speed with the starboard stern under the wind.
How to judge whether the typhoon is far away?
Does it mean that the typhoon has been far away? When the storm stops suddenly, it may be a phenomenon that enters the eye of the typhoon, not that the typhoon has been far away, in a short time, the storm will suddenly come again.Thereafter, the wind and rain gradually decreased, and became intermittent rainfall, slowly, the wind became smaller, the clouds rose, and the rain stopped,that is when the typhoon left.If the eye of the typhoon does not pass through the local area, but the wind direction gradually changes from a northerly wind to a southerly wind, and the wind and rain gradually become smaller, the pressure gradually rises, the clouds gradually dissipate, and the weather turns better, which also means that the typhoon is moving away.
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