Typhoons and hurricanes are both strong tropical cyclones generated on the surface of tropical oceans, but they are called differently. Tropical cyclones that occur in the western part of the North Pacific Ocean and west of the international international date line, including the South China Sea, are called typhoons. Tropical cyclones in the Atlantic Ocean or the eastern North Pacific Ocean are called hurricanes, which means hurricanes in the United States and typhoons in the Philippines, China and Japan.
Typhoons are often accompanied by strong winds and heavy rains. The wind rotates counterclockwise. Isobars and isotherms are approximately a set of concentric circles. The central air pressure is the lowest and the temperature is the highest.
Formation of typhoon
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. The typhoon occurred on the ocean surface about 5 latitudes from the equator.
Classification of typhoons
Super typhoon: the maximum average wind speed near the center of the ground layer is ≥ 5 1.0m/s, that is, 16 or more.
Strong typhoon (STY): The maximum average wind speed near the bottom center is 41.5-50.9m/s, which is 14- 15.
Typhoon (TY): the maximum average wind speed near the center of the ground floor is 32.7-4 1.4m/s, which is 12- 13.
Severe tropical storm (STS): the maximum average wind speed near the bottom center is 24.5-32.6m/s, that is, wind10-1.
Tropical storm (TS): the maximum average wind speed near the bottom center 17.2-24.4m/s, that is, the wind force is 8-9.
Tropical depression (TD): the maximum average wind speed near the bottom center 10.8- 17. 1 m/s, that is, the wind force is 6-7.
The path of typhoon
The direction and speed of typhoon movement depend on the force acting on the typhoon. Power is divided into internal force and external force. The internal force is the resultant force from north to west caused by the different geostrophic skewness caused by the latitude difference between north and south within the typhoon range. The larger the typhoon range, the stronger the wind speed and the greater the internal force. The external force is the force of the external environment flow field on the typhoon vortex, that is, the guiding force of the easterly belt of the basic airflow on the south side of the subtropical high in the northern hemisphere. Internal force mainly plays a role in the initial generation of typhoon, while external force is the leading force to manipulate the movement of typhoon, so typhoon basically moves from east to west. Due to the influence of the shape, position and intensity of subtropical high, the typhoon's moving path is not uniform and becomes diverse. Taking the typhoon moving path in the northwest Pacific as an example, there are three moving paths:
(1) The westward typhoon moved from the east of the Philippines to the west, crossed the South China Sea, and finally landed on Hainan Island in China or northern Vietnam. This route mostly occurs in 10- 1 1, and 2006 is a typical example.
(2) Landing type: The typhoon moved to the northwest, crossed the Taiwan Province Strait, landed in the coastal areas of Guangdong, Fujian and Zhejiang, and gradually weakened into a low pressure. This typhoon has the greatest impact on China. The two typhoons "90 15" and "97 1 1" which have had the greatest impact on Jiangsu in recent years belong to this type, and basically follow this path from July to August.
(3) Parabolic type: the typhoon first moves to the northwest, turns to the northeast when approaching the eastern coast of China, and turns to the vicinity of Japan. The path is parabolic, mostly occurring in May-June and 9-165438+1October.
After the typhoon is formed, it will generally move out of the source and experience the evolution process of development, weakening and extinction. A mature typhoon has a circular vortex radius of 5 OOKM ~ 1000 km and a height of 15 km ~ 20 km. Typhoon consists of three parts: peripheral area, maximum wind speed area and typhoon eye. The wind speed in the peripheral area increases from outside to inside, with spiral clouds and precipitation; The strongest precipitation occurs in the maximum wind speed area, with an average width of 8 km ~ 19 km, and there is a circular cloud wall between it and the typhoon eye; The typhoon eye is located in the center of the typhoon. The most common typhoon eye is round or oval, ranging in diameter from 10 km to 70 km, with an average of about 45km. The weather in typhoon eye is calm, partly cloudy, dry and warm.
The origin of a word
The word hurricane comes from the Caribbean devil hurrican, and some people say that Hurakan, the god of thunderstorms and cyclones, is one of the creation gods in Mayan mythology. The word typhoon comes from Tifeng, the son of Gaia, the mother of the earth in Greek mythology. It is a monster with a hundred faucets. It is said that its children are terrible winds.
As for the Chinese word "typhoon", some people say it comes from Japanese, while others say it comes from China. In the past, there were frequent storms along the southeast coast of China, which were called "gale" by local fishermen and later turned into typhoons.
Discrimination of hurricane concept
Both hurricanes and typhoons refer to tropical cyclones with wind speeds exceeding 33 m/s, but they have different names because of different regions. Strong tropical cyclones appearing in the northwest Pacific Ocean and the South China Sea are called "typhoons"; Hurricanes that occur in the Atlantic Ocean, the Caribbean Sea and the eastern North Pacific Ocean are called "hurricanes". Hurricanes can release amazing energy in one day. Hurricanes and tornadoes cannot be confused. The latter time is very short, and it is instantaneous, and the longest is no more than a few hours. In addition, tornadoes are usually accompanied by hurricanes. The biggest feature of tornado is that when it appears, it often has one or several funnel-shaped cloud columns similar to "trunk", accompanied by storm, lightning or hail. When a tornado passes through the water, it can absorb water and rise to form a water column, and then connect with the cloud, commonly known as "dragon with water". When passing through land, houses are often rolled down, and even people are sucked into the air.
Classification of hurricanes
Level one. The maximum sustained wind speed is 33–42m/s, 74–95mph, 64–82mph19–153km/h, the storm surge is 4–5ft1.2–1.5m, and the minimum pressure in the center is 28.94 inches of mercury. Some coasts will be flooded and small docks will be damaged. Typical Hurricane Agnes-Hurricane Danny-Hurricane gaston-Hurricane O 'filia.
Level two. The maximum sustained wind speed is 43-49 m/s 96- 1 10 mph 83-95 knots 154- 177 km/h storm surge 6-8 ft 1.8-2.4 m. 1006/0005 Typical Hurricane Bob-Hurricane Bonnie-Hurricane Francis-Hurricane Juan
Level three. The maximum sustained wind speed is 50–58m/s11–130mph 96–113kt178–209km/h storm surge 9– Floods near the coast destroyed buildings, large and small, and flooded the inland. Typical Hurricane 1938 New England Hurricane Fran Hurricane isidore Jenny.
Level 4. The maximum sustained wind speed is 59–69 m/s131–155 mph14–135 knots/210–249 km/h storm surge/kloc. Most areas near the sea were flooded, and inland floods occurred on a large scale. Typical Hurricane 1900 Galveston Hurricane Charlie Hurricane Hugo Iris
Level 5. Maximum sustained wind speed ≥ 70m/s ≥156mph ≥136kt ≥ 250km/h storm surge ≥ 19 ft ≥5.5 m central minimum pressure.
The harm of hurricane
In the northern hemisphere, the typhoon rotates counterclockwise, while in the southern hemisphere, it rotates clockwise. Usually accompanied by strong winds and heavy rains, it seriously threatens the safety of people's lives and property and has a great impact on people's livelihood, agriculture and economy. This is a serious natural disaster.
Cause and effect
One reason why tropical oceans produce hurricanes is that warm seawater is its power "fuel". Therefore, some scientists began to study whether the warming earth will bring more powerful and harmful tropical storms. Most meteorologists believe that the earth seems to be getting hotter and hotter. They think that carbon dioxide and so-called greenhouse gases in the atmosphere are warming the earth. Researchers warn that people must seriously think about the problem of global climate change decades or even centuries later. It should be pointed out that a weather and climate event, such as a strong hurricane or an active hurricane season, does not mean global warming.
Tornado (tornado)
Tornado is a kind of vortex: the air rotates rapidly around the axis of tornado and is attracted by the extremely low air pressure in the center of tornado. In the thin layer of air tens of meters thick near the ground, the airflow is sucked into the bottom of the vortex from all directions. Then it becomes a vortex around the axis. The wind in a tornado is always cyclonic, and the air pressure in its center can be 10% lower than that around it.
A tornado is a strong wind vortex accompanied by a funnel-shaped cloud column rotating at high speed. The wind speed near the tornado center can reach 100 m/s to 200 m/s, with a maximum of 300 m/s, which is several times larger than the maximum wind speed near the typhoon center. The central air pressure is very low, generally as low as 400 hectopascals and as low as 200 hectopascals. It has a great sucking effect, which can suck the sea (lake) water away from the sea (lake) surface, form a water column, and then connect with the clouds, commonly known as "dragon water absorption". Because the air inside the tornado is extremely thin, the temperature drops sharply and the water vapor condenses rapidly, which is an important reason for the formation of funnel cloud column. The average diameter of the funnel cloud column is only about 250 meters. Tornadoes are produced in very unstable cumulonimbus clouds. Its formation is related to the strong rise of warm and humid air, the southward movement of cold air and topography. Its life history is short, usually lasting ten minutes to an hour or two, but its destructive power is amazing. It can uproot trees, blow down buildings or roll some ground objects into the air. There are tornadoes in Jiangsu Province almost every year, but the location has no obvious regularity. It usually appears in June and July, sometimes in early or middle August.
Tornado formation
Tornadoes are the product of thunderstorms in the clouds. Specifically, a tornado is a form in which a small part of the huge energy of a thunderstorm is released in a small area. The formation of tornadoes can be divided into four stages:
(1) The instability of the atmosphere produces a strong updraft, which is further strengthened due to the influence of the maximum transit airflow in the rapids.
(2) Due to the interaction with the wind with shear speed and direction in the vertical direction, the updraft starts to rotate in the middle of the troposphere, forming a mesoscale cyclone.
(3) With the development and upward extension of mesoscale cyclone to the ground, it becomes thinner and stronger. At the same time, a small area to strengthen cooperation, that is, the primary tornado is formed inside the cyclone, and the same process of producing the cyclone forms the tornado core.
(4) The rotation in the tornado core is different from that in the cyclone, and its intensity is enough to make the tornado extend to the ground. When the developing vortex reaches the ground, the ground air pressure drops sharply and the ground wind speed rises sharply, forming a tornado.
Tornadoes often occur in thunderstorm weather in summer, especially in the afternoon to evening. The attack range is small, and the diameter of tornadoes is generally between ten meters and several hundred meters. The survival time of tornadoes is generally only a few minutes, and the longest is no more than a few hours. The wind is particularly strong, and the wind speed near the center can reach 100-200m/s, which is extremely destructive. Where tornadoes pass, trees are often pulled up, vehicles are overturned, buildings are destroyed, and sometimes people are sucked away, which is very harmful.
Hazards of tornadoes:
1995 In a tornado in Admore, Oklahoma, USA, heavy objects such as roofs were blown dozens of miles away. Most of the debris falls on the left side of the tornado passage, and there are often obvious landing areas according to the weight. Lighter debris may fly more than 300 kilometers before landing.
The tornado struck suddenly and violently, and the wind force produced was the strongest on the ground. In the United States, the number of deaths caused by tornadoes is second only to lightning every year. Its damage to buildings is also quite serious, often devastating.
Under the attack of a strong tornado, the roof of the house will fly like a glider. Once the roof is swept away, the rest of the house will collapse. Therefore, if we can strengthen the stability of the roof when building houses, it will help to prevent the tornado from causing huge losses when crossing the border.
Precautionary measures for tornadoes
(1) At home, be sure to stay away from doors, windows and external walls of houses and hide in the wall or small room opposite the tornado. The safest place to avoid a tornado is the basement or semi-basement.
(2) In case of emergency such as pole collapse and house collapse, the power supply should be cut off in time to prevent electric shock or fire.
(3) When there is a tornado outside the venue, you should look for low-lying land nearby, but stay away from trees and telephone poles to avoid being smashed, crushed and electrocuted.
(4) When the car encounters a tornado when going out, you must not drive to avoid it, nor do you avoid it in the car, because the car has almost no defense ability against tornadoes. You should leave the car immediately and avoid it in a low-lying place.
1On May 27th, 999, four counties in central Texas, including Austin, the capital, were hit by a huge tornado, killing at least 32 people and injuring dozens. It is reported that in jarrell, 40 miles north of Austin, more than 50 houses collapsed and more than 30 people were killed in the tornado. The damaged area is 1 mile long and 200 yards wide. This is another tornado area in the United States after Miami was hit by a tornado on May 3, 65438.
Generally speaking, a tornado is a whirlwind. When it touches the ground, its diameter ranges from several meters to 1 km, with an average of several hundred meters. Tornadoes range from a few meters to dozens of kilometers, and things are robbed everywhere. The funnel-shaped center of tornado is composed of inhaled dust and condensed water vapor, which is a visible "dragon mouth". On the ocean, especially in the tropics, similar scenes are called sea tornadoes.
Most tornadoes rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, with some exceptions. The exact mechanism of tornado formation is still under study, and it is generally believed to be related to the violent activities of the atmosphere.
Since19th century, the accuracy of weather forecast has been greatly improved, and various disasters and storms such as tornadoes and hurricanes can be detected by weather radar.
1995 In a tornado in Admore, Oklahoma, USA, heavy objects such as roofs were blown dozens of miles away. Most of the debris falls on the left side of the tornado passage, and there are often obvious landing areas according to the weight. Lighter debris may fly more than 300 kilometers before landing.
The tornado struck suddenly and violently, and the wind force produced was the strongest on the ground. In the United States, the number of deaths caused by tornadoes is second only to lightning every year. Its damage to buildings is also quite serious, often devastating.
Under the attack of a strong tornado, the roof of the house will fly like a glider. Once the roof is swept away, the rest of the house will collapse. Therefore, if we can strengthen the stability of the roof when building houses, it will help to prevent the tornado from causing huge losses when crossing the border.
Tornadoes are usually extremely fast. It is not surprising that the wind speed is 100 m per second, even reaching more than 175 m per second, which is five or six times larger than the typhoon 12. The range of wind is very small, generally the diameter is only 25~ 100 meters, and only in rare cases can the diameter reach more than one kilometer; It takes only a few minutes from occurrence to disappearance, at most a few hours.
Tornadoes are also very powerful. On September 24th, 1956, a tornado appeared in Shanghai. It easily lifted a large oil storage barrel weighing 220,000 Jin to the altitude of15m, and then threw it away from120m.
Tornadoes, also known as cyclones in America, are common natural phenomena. Cyclones are often more destructive than earthquakes.
1879 at 4 pm on may 30, two dark and thick clouds were merging over northern Kansas. After 15 minutes, a vortex was generated at the lower end of the cloud. The vortex has grown rapidly and become a huge pillar of indomitable spirit. Within three hours, it ran wild all over the state like a dragon, and no one was spared wherever it went. However, the strangest thing happened at the beginning, when the tornado whirled across a small river and met a cliff. Obviously, it is impossible to surpass this obstacle, so the vortex turns to the west, and there happens to be a newly built 75-meter-long railway bridge over there. The tornado vortex actually pulled it down from the stone pier, twisted it a few times, and then threw it into the water.
introduce
Cyclone is a kind of rotating air vortex, which flies into the air with dust carried by the ground. This vortex is what we usually see, and it is a natural phenomenon caused by air flow.
cause
When the air flows around the uneven places such as trees, hills and buildings on the ground, or when the air rubs against the ground, its forward direction will change rapidly, and then a vortex moving with the airflow will be generated, thus blowing a whirlwind. However, this kind of cyclone is very rare and very small.
The main reason for the formation of cyclones is that when a place is very hot by the sun, the air here will expand and some air will be squeezed up. After reaching high altitude, the temperature will gradually decrease, start to flow around and finally sink to the ground. At this time, the air in the heated area decreases, and the air pressure also decreases, while the surrounding temperature is low and the air density is high. In addition, the heated air falls from the air, so the air increases and the air pressure increases significantly. In this way, air will flow from the places with high air pressure around to the places with low air pressure in the center, just like water flowing downwards. However, because the air flows on the earth, and the earth is constantly rotating from west to east, the air will be influenced by the rotation of the earth in the process of flowing, and gradually shift to the right (the original north wind is deflected into northeast wind, the south wind into southwest wind, the west wind into northwest wind, and the east wind into southeast wind). So the cold air blowing from all directions rotates around the heated low pressure area, becoming an air vortex opposite to the clockwise rotation direction of the clock, forming a whirlwind.
In the center of this cyclone, due to the rising warm air and the continuous rotation of the surrounding air, it is easy to roll the dust, leaves and scraps of paper on the ground into the air and fly with the airflow. If the cyclone is very strong, sometimes some small animals on the ground, such as small snakes and bugs, will be swept into the air and gone with the wind in the dust.
Generally, the height of a small cyclone is not too large. When it is rubbed by the ground or blocked by houses and trees, it gradually dissipates and becomes an ordinary wind.
Some people may ask: because the ground is easy to produce cyclones when heated, it is hotter in summer than in spring. Why are there fewer cyclones in summer and more cyclones in spring? This is because although the weather is very hot in summer, the ground vegetation is green, the land is wet, and the temperature difference is not big, so there are few cyclones in summer. But in spring, the leaves haven't grown, the grass has just sprouted, the farmland is bare, there is no shelter everywhere, and it is easy to get hot, which makes the air temperature on the ground change greatly and it is easy to blow a whirlwind.
Cyclones can fly into the air with dust and messy papers, and of course, they can also bring heat and water vapor from the ground to the air, so they cause vertical mixing of heat and water vapor in the air and make the vertical distribution of heat and water vapor even. The cyclone near the surface is very small, and the vertical exchange effect is not great, so a special microclimate is formed in the gas layer near the surface.
In addition, strong tropical cyclones occurring in the southern hemisphere and the northern Indian Ocean are also called cyclones.