Lightning is accompanied bylightningandThunderIt is a magnificent and somewhat daunting discharge phenomenon.The conditions for lightning areThunderstorm cloudAccumulation and formationPolarity。
According to different terrain and meteorological conditions, lightning can generally be divided into three categories: hot lightning, front lightning (hot front lightning and cold front lightning) and terrain lightning.
The water vapor in the atmosphere is the internal cause of thunderstorm formation;The formation of thunder clouds is also related to the natural terrain and meteorological conditions.
1. Thermal lightning is a kind of lightning that often occurs in the afternoon in summer, often accompanied by rainstorm or hail.The thermal lightning is formed quickly and lasts for 1~2 hours;The length of the minefield shall not exceed 200-300km and the width shall not exceed tens of kilometers.The formation of thermal lightning must meet the following conditions.
(1) The air is very humid, and the water vapor in the air is nearly saturated, which is a necessary factor for the formation of thermal lightning.
(2) In sunny summer, when the sun is hot, the ground is permanently exposed to the sun, the temperature of the humid air near the ground rises rapidly, and people feel sultry, which is a necessary condition for the formation of hot lightning.
(3) There is no wind or light wind, resulting in uneven air humidity and temperature.The reason why there is no wind or light wind may be that the airflow changes little here, or it may be because of the terrain (such as a basin in the mountains).
The above conditions gradually form clouds, and at the same time the clouds form thunderclouds due to polarization.The above conditions are mostly found in inland areas, especially in valleys and basins.
2. Strong cold air flow or warm air flow invades some place at the same time, and the front or nearby where the cold and warm air contacts mayproduceCold front thunder and lightning.
(1) The formation of cold front thunder (or cold wave thunder) is that when a strong cold air flow invades from north to south, because the cold air is heavier, the cold air flow is like a wedge inserted under the original warm and humid air, forcing the warm air to rise, the hot and humid air to rise to a certain height, and the vapor reaches saturation, gradually forming thunder clouds.Cold front thunder is the strongest kind of thunder and lightning. It is usually accompanied by heavy rain, which is very harmful.This kind of thunderstorm generally develops along a belt shaped area hundreds of kilometers long and 20 to 60 kilometers wide of the front. The front moves at a speed of 50 to 60 kilometers per hour, up to 100 kilometers per hour.
(2) The formation of warm front thunder (or heat wave thunder) is caused when warm air flows to cold air areas and gradually climbs onto cold air.Its occurrence is generally more moderate than that of cold front thunder, and strong thunderstorms rarely occur.
3. Topographic lightning generally occurs in open terrain areas, which is small in scale but frequent.
Phenomenon Introduction
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"Lightning" natural phenomenon
Lightning is accompanied bylightningandThunderOne ofmajesticAnd a little bitAwesomeOfDischarge phenomenon。Lightning is generally generated fromconvectionExuberantCumulonimbus cloudMedium, so it is often accompanied by strong gusts, rainstorm, and sometimeshailandtornado。The top of the cumulonimbus cloud is generally high, up to 20 kilometers, and the upper part of the cloud often hasIce crystal。Glaze attachment of ice crystals,Water dropBroken andatmosphereConvection, etcprocess, make the cloud producecharge。The distribution of charge in the cloud is complex, but in general, the upper part of the cloud ispositive chargeMainly, the lower part is negativechargeMainly.Therefore, the upper and lower parts of the cloud form apotentialPoor.WhenpotentialWhen the difference reaches a certain level, there will be discharge, which is our common lightning phenomenon.The average current of lightning is 30000 amperes, and the maximum current can reach 300000 amperes.LightningVoltageVery high, about 100 million to 1 billionVolts。A medium strengththunderstormOfpowerUp to 10 million watts, equivalent to a small buildingnuclear power plantOfoutput power。During discharge, due toLightning passageintemperatureSurgeGasThe product expands rapidly, resulting in shock waves and strong thunder.When charged thunderclouds are close to the protrusions on the ground, intense discharges occur between them.Strong flash andblastThe roar of.This is the lightning that people see and hearThunder。
type
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Continuous lightning
Lightning minuteDirect lightning strike、electromagnetic pulse , spherical thunder and cloud flash.Direct lightning strike and spherical lightning will cause harm to people and buildings, while electromagnetic pulse mainly affectsElectronicsEquipment, mainly caused by induction;Cloud flashBecause it occurs between two clouds or on both sides of a cloudMinimal hazard。
The direct lightning strike isCloud bodyGather a lot of electric charges on the,Large chargeTo find a way to release, sometimes it is a building, sometimes it is an iron tower, sometimes it is a person in an open place, so these people orobjectIt becomes a channel for discharging electric charges, and people or buildings are injured.Direct lightning is the most powerful lightning, while spherical lightning is less powerful than direct lightning.
Formation of thunderclouds
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The conditions for lightning areThunderstorm cloudIt accumulates and forms polarity.scientistThe charging mechanism and charge of thunderstorm clouds arelawA lot of observations and experiments have been carried out, a lot of data have been accumulated, and various explanations have been put forward. Some arguments are still controversial.
1. The initial stage of convective cloud“IonsFlow hypothesis
There are a lot ofPositive ionandanionOn the raindrops in the cloud, the charge distribution is uneven, and the outermost molecular bandnegative electricity, inner beltpositive electricity, inner layer than outer layerpotentialThe difference is about 0.25V higher.in order tobalancethisPotential differenceThe water drop must first absorb the negative ions in the atmosphere, which gradually makes the water drop negatively charged.WhenconvectionAt the beginning of development, the lighter positive ions are gradually carried to the upper part of the cloud by the rising air flow;The negatively charged cloud droplets, because they are relatively heavy, stay at the lower part, resulting in positivenegative chargeOfseparate。
2. Charge accumulation of cold clouds
When the convection develops to a certain stage and the cloud body reaches the height above 0 ℃, supercooled water droplets, graupel particles and ice crystals will appear in the cloud.The water vapor with different phase statescoagulationClouds composed of substances and whose temperature is lower than 0 ℃ are called cold clouds.The processes of charge formation and accumulation of cold clouds are as follows:
① Supercooled water drops on graupel grains and freezes to generate electricity
There are many water drops in the cloud layer that will not freeze when the temperature is lower than 0 ℃. This kind of water drop is called supercooled water drop.Supercooled water droplets are unstable as long as they are gentlyearthquakeMove it and freeze the scale immediatelyIce granule。When supercooled water drops collide with graupel particles, they will freeze immediately, which is called bump freezing.When freezing occurs,Supercooled waterThe outside of the drop immediately freezes into an ice shell, but the inside of the drop remains liquid for the time being, and because the latent heat from the outside freezing is transferred to the inside, the temperature of the internal liquid supercooled water is higher than that of the outside ice shell.The difference in temperature makes the frozen supercooled water droplets positively charged externally and negatively charged internally.When internal freezing also occurs,Cloud dropIt expands and splits, and the outer skin breaks into many positively charged ice particles, which fly to the upper part of the cloud layer with the airflow, and negatively charged frozen dropletscoreSome of them are attached to the heavier graupel particles, making the graupel particles negatively charged and remaining in the middle and lower part of the cloud layer.
② Ice crystal and graupelfrictionCollision electrification
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Graupel particles are composed of frozen water droplets, which are white or milky white and have a relatively brittle structure.Because cold water drops often collide with it and release itlatent heatIts temperature is generally higher than that of ice crystals.There are a certain amount of free ions (OH - and H+) in ice crystals, and the number of ions increases with temperature.Due to the temperature difference between graupel particles and ice crystals,high temperatureThere must be more free ions at the high temperature end than at the low temperature end, so the ions must migrate from the high temperature end to the low temperature end.Ion migrationPositiveHydrogen ionFaster, but heavier with negative chargeHydroxyl ionIs slower.Therefore, the phenomenon of excess cold end hydrogen ions appeared within a certain period of time, resulting inhigh temperatureNegative at the end, positive at the low temperature endelectrodeChange.When the ice crystal contacts the graupel and separates, the graupel with higher temperature is negatively charged, while the ice crystal with lower temperature is positively charged.staygravityAnd updraft, the lighter and positively chargedIce crystalConcentrate on the upper part of the cloud, and the heavier negatively charged graupel particles stay at the lower part of the cloud layer, resulting in positive electricity in the upper part of the cold cloud and negative electricity in the lower partnegative electricity。
③ The water drop is electrified due to the thin salt content
In addition to the two starting mechanisms of the cold cloud mentioned above, others have proposed the generating mechanism due to the thin salt content of water droplets in the atmosphere.WhenCloud dropWhen frozen, the ice lattice can hold negative chloride ions, but repel positive sodium ions.Therefore, the frozen part of the water drop is negatively charged, while the unfrozen part is positively charged (the water drop is frozen from the inside out).During the falling process of graupel particles formed by freezing water droplets, the water on the surface that has not yet been frozen is dropped, forming many small cloud droplets with positive electricity, while the frozen core is negatively charged.Due to the separation effect of gravity and air flow, positive droplets are brought to the upper part of the cloud, while negative graupel particles stay in the middle and lower parts of the cloud.
3. Charge accumulation of warm clouds
In the tropics, there are some clouds and the whole cloud body is located above 0 ℃.Therefore, it only contains water droplets, but notsolid statewaterparticle。Such clouds are called warm clouds or water clouds.Warm clouds can also cause lightning.In mid latitudeThunderstorm cloud, cloud body at 0 ℃isothermThe following part is about the cloudWarm zone。In the warm zone of cloudsPower onThe process occurs.
In the development process of thunderstorm clouds, the upper number mechanism plays a role in different development stages.However, the main electrification mechanism is due toWater dropCaused by freezing.A large number of observational facts show that only when the cloud top appearsfibreThe cloud develops intoThunderstorm cloud。Aircraft observation found that there were a large number of cloud particles, mainly ice, snow crystals and graupel particles, andchargeThe accumulation of thunderstorm cloud, namely, thunderstorm cloud rapid band electric mechanism, must rely on the collision, freezing and friction of graupel grains in the growth process.
Lightning type
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The ordinary lightning with zigzags and forks is calledDendritic lightning。If the branch lightning channel is blown to both sides by the wind, so that it seems that there are several parallel lightning, it is calledBanded lightning。If the two lightning branches seem to reach the ground at the same time, they are calledForked lightning。
When lightning flashes between the negative and positive charges in the cloud, and makes the whole sky bright, it is calledFlaky lightning。
Lightning that does not reach the ground, that is, lightning in the same cloud layer or between two clouds, is calledCloud lightning。Sometimes this kind of horizontal lightning will walk for a distancestormMany kilometers away from the ground, this is called "thunderbolt".
The electric action of lightning sometimes forms a halo of red light around tall and sharp objects.Usually instormOn the sea in the rain, a fiery light can be seen around the mast of the ship. People use the name of the patron saint of sailors to call this lightning“St. Elmo's Fire ”。
Super lightningIt refers to rare lightning that is more than 100 times more powerful than ordinary lightning.The electricity generated by ordinary lightning is about 1 billionwattThe power generated by super lightning is at least 100 billion watts, and may even reach trillions to 100000 billion watts.
stormClouds usually generate electric charges. The bottom layer is negative, the top layer is positive, and it also generates positive on the groundcharge, follow the cloud like a shadow.Positive and negative charges attract each other, but air is not a good conductor.Yang Dian rushes to the top of trees, hills, tall buildings and even the human body, attempting tonegative electricityThe clouds meet;The negative charge dendritic antenna extends downward, and the more downward it extends, the closer it is to the ground.Finally, the negative and positive charges finally overcome the air barrier and connected.The huge current flows from the ground to the clouds along a conductive airway, producing a bright and dazzling flash.The length of a lightning bolt may be only several thousand meters, but the maximum length can be hundreds of kilometers.
The temperature of lightning varies from 17000 ℃ to 28000 ℃, which is equal to 3~5 times the surface temperature of the sun.The extreme heat of lightning makes the air expand violently along the way.The air moves rapidly, thus formingwaveAnd make a sound.lightningIf you are close, you will hear a sharp popping sound;If you are far away, you will hear a rumble.After you see the lightning, you can start the stopwatch. When you hear the thunder, you can press it to stop, and then divide the number of seconds obtained by 3 to roughly know the flashionizationYou have thousands of meters.
Activity pattern
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1. The general conditions of lightning activities are as follows.
(1) Geological conditions: When the relative value of soil resistivity is small, it is conducive to the rapid accumulation of charges.Places with small local resistivity are vulnerable to lightning strike;The sudden change of resistivity and underground conductive mineral deposits are easy to be struck by lightning;In fact, the resistivity of grounding grid will increase the probability of lightning strike.
(2) Topographic conditions: the valley trend is consistent with the wind direction, and the tuyere or downwind valley is vulnerable to lightning;Mountain slopes near lakes and seas are more likely to be struck by lightning.
(3) Surface conditions: it is conducive to establishing a good discharge channel between thunderstorm clouds and the earth.The isolated buildings in the open land and the high-rise buildings in the building group are vulnerable to lightning;Big trees, receiving antennas and transmission lines in mountainous areas are vulnerable to lightning strikes;In line with the characteristics of tip discharge, the probability of lightning strike will also increase after the completion of the base station tower.
2. According to engineering experience, the following places may be places with high probability of lightning damage.
(1) Soil resistivity at 10m depthrtenThe place where the mutation occurs.
(2) Some geological fault zones are located at the junction of rocky mountains, paddy fields and rivers, at the boundary of mineral deposits, at the boundary of mountain entering forests.
(3) Mountain Yueyang slope or windward slope facing vast waters.
(4) A high, isolated mountain top.
(5) Places where lightning damage has occurred repeatedly in the past.
(6) Isolated towers and guy wires, high-rise buildings and other grounding protection devices nearby.
Time of attack
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At every moment, there are about 1800 lightning strikes in progress around the world.They send out about 600 lightning flashes per second, 100 of which strike the earth.[1]
UgandacapitalKampalaAnd IndonesianJavaIs the most vulnerable place to lightning.According to statistics, there were 300 days of lightning in Java one year.The most violent lightning strike in history was in 1975zimbabweTwenty one people died in a small house near Umtari in the countryside.
Frequency and characteristics
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At any given moment, there are 1800 games in the worldthunderstormIs happening, about 100 times per secondLightning strike。stayU.S.A, lightning will cause about 150 people every yeardeathAnd 250 injured.More than 4000 people are struck by lightning every year in the world.On flat terrain with an average lightning frequency, every 300 foot tall building will be hit once a year on average.Each 1200 foot building, such as radio orTV Tower, will be hit 20 times every year, and each lightning strike will usually produce 600 million voltshigh pressure。
Each lightning from the cloud to the ground actually contains three to five independent lightning strikes within 60 millisecond intervalspeak current It is about 20000 amperes, and the peak current of subsequent lightning stroke is halved.After the last lightning stroke, there may be a continuous current of about 150 amperes lasting for 100 milliseconds.
throughmeasureThese lightning strikesrise time About 200 nanoseconds or faster.Through 20000 amperes and 200 nanoseconds, it is not difficult to calculate that the value of dI/dt is 10 ^ 11 amperes per second.
harm
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More than two-thirds of lightning victims were attacked outdoors.Two out of every three of them survived.Of the people killed by lightning, 85% are men, mostly between the ages of 10 and 35.Most of the dead took shelter from thunderstorms under trees.[2]
Sullivan may be the champion hit by lightning.He is a retired forestadministrators, was struck by lightning 7 times.Lightning once scorched his eyebrows, burned his hair, burned his shoulders, pulled away his shoes, and even threw him outside the car.He said lightly: "Lightning always finds me."
The harm of lightning to human body includes direct action of current, overpressure or dynamic action, and high temperature action.When a person is struck by lightning, the current quickly passes through the human body, which can lead to cardiac arrest and respiratory arrest, and death due to lack of oxygen in brain tissue.In addition, lightning strikesspark, can also cause varying degrees of skin burns.Lightning injury can also cause dendritic lightning lines, skin peeling, and intradermal bleeding on the human bodyTympanic membraneOr visceral rupture, etc.
China is more than onenatural disasterThe country and geographypositionThere are many lightning disasters in China, the most serious of which isGuangdong ProvinceTo the south,Dongguan, ShenzhenHuizhouThe natural disasters of thunder and lightning have reachedThe most in the worldThese places are also affected by the relatively low atmospheric position.Dongguan in China is the most serious. The economic losses caused by thunder and lightning occurred between May and August in the summer. The proportion of GDP loss in Dongguan in the current quarter is close to 6%. The economic losses of tens of millions are also a serious natural disaster prone area.A number of lightning injuries occur every year in Dongguan, which is the most frequent and largest area in the world.It is one of the hardest hit areas of lightning in China and even the world.
Special effects of lightning on biological pathological cells
As we all know, lightning originates from cumulonimbus clouds in summer.When the charged cloud layer is close to the tall buildings on the ground, the positive and negative charges will collide and form a strongflash of light, accompanied by airresonanceThere is a huge roar, which is thunder and lightning.Sometimes people call lightning lightning.Why is it called thunder and lightning?Because "thunder" symbolizes explosion“ThunderThe "thunder" in "lightning" describes sound, while "lightning" is light formed due to the impact of positive and negative chargesradiation, so people willnatureThunder and lightning in are collectively called thunder and lightning.The lightning voltage is very high, about 100 million to 1 billion volts. The power released by a moderate lightning can be as high as 10 million watts, equivalent to the output power of a small nuclear power plant.Lightning rod can only prevent the strong charge impact of direct lightning strike, but it canelectromagnetic inductionIt's hard to work.Lightning is divided into contact charge andInduced electricityHe.
(1) Contact charge: In the strong cumulonimbus clouds, due to the continuous accumulation of charges, a strongstatic electricityhigh pressureelectric field。stayElectric field forceUnder the action ofTip dischargeTo unload the charge.In this case, the cloud layer carries a positive charge, and the earth carries a positive chargenegative charge。When positive and negative charges collide with each other, it will form an instantNeutralization reactionThis is also called direct lightning strike.
(2) Inductive charge: at the moment of cloud discharge, powerful electromagnetic conversion is formedmagnetic fieldAn induced charge will form on the metal conductor on the earth's surface.This induced charge will accumulate in an instant to form a high-voltage electric field discharge, which will cause the communication network and electrical equipment to be destroyed in an instant.
Thunder and lightning will cause great damage to human life. The direct economic loss caused to human beings in the thunderstorm season every year is up to hundreds of millions of dollars. The number of people and other animals killed by lightning every year is staggering, and the number is still rising.The harm of lightning to human body mainly includes two types:
(1) Direct lightning stroke: when a person is struck by lightning, a strong current will quickly pass through the human body, which can lead to cardiac arrest, pulmonary failure, and brain hypoxia and death in serious cases.In addition, the high temperature arc light generated by lightning stroke will also cause skin burns and carbonization of human body to varying degrees.When the human body is struck by lightning, it will form dendritic lightning strike texture, resulting in skin peeling and bleeding, as well as ear drum and viscera rupture.In addition, according to incomplete statistics, in the annual thunderstorm season, the number of lightning strikes in the world is up to 1700, and there are about thousands of people suffering from lightning strikes every year.On relatively flat terrain, buildings about 30 meters high are hit once a year on average;Every high-rise building, such as a radio or television tower, which is tens of meters or more in height, will be hit about 20 times a year, and the high voltage generated by each lightning strike is about 600 million volts.Without lightning protection equipment, these buildings would have been destroyed long ago.From cloud to groundlightningLightning strikes also include the number of occurrences within the interval of about 50 milliseconds, that is, about 4 independent lightning strikes.The peak current of the first lightning stroke is about 20000 amperes, while the peak current of the subsequent lightning stroke will be halved. The last lightning stroke is likely to produce a continuous current of about 140 amperes, which can last for tens of milliseconds.
(2) LeiinductanceShould.Is onlightning induction Powerful moments in the processelectromagnetic field, this powerful induced magnetic field can generate induced charges in the ground metal network.Including wired and wireless communication networks, power transmission networks and othersMetallic materialsFinished line system.High intensity induced charge will form a strong instantaneous high-voltage electric field in these metal networks, thus forming a high voltage to electrical equipmentArc discharge, which will eventually lead to the burning of electrical equipment.In particular, the damage to weak current equipment such as electronics is the most serious, such as TV sets, computers, communication equipment, office equipment, etc. of household appliances.Every year, byInduction thunderThere are more than ten million accidents of electric equipment destroyed by electricity.This high-voltage induction can also cause personal injury.
Lightning protection instructions
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Generated when lightning occursLightning currentIt is the main source of damage, and its hazards includeDirect lightning strikeInductive lightning strike and intrusion lightning guided by overhead line.For example, overhead lines used by various lighting, telecommunications and other facilities may lead lightning into the room, so strict precautions should be taken.
Parts prone to lightning strike
1. Tall buildings and storage tanks lacking or unqualified lightning protection equipment
2. Metal roof without good grounding
3. Buildings, trees, etc. in wet or open areas
4. Due to the conductivity of flue gas, chimney is particularly vulnerable to lightning strike
1. Pay attention to closing doors and windows, and indoor personnel should stay away from doors and windows, water pipes, gas pipes and other metal objects.
2. Turn off the household appliances and unplug the power plug to prevent thunder and lightning from invading the power line.
3. When you are outdoors, you should avoid in time and do not stay in the open field.When there is no place to hide in the open field, try to find a low-lying place (such as a pit) to hide, or squat down immediately to reduce the height of the body.
4. Keep away from isolated trees, towers, poles and billboards
5. Immediately stop outdoor swimming, boating, fishing and other water activities.
6. If many people live outdoors, do not squeeze against each other to prevent current conduction after lightning stroke.
Expert tips:
1. Lightning protection devices must be installed on tall buildings to prevent lightning disasters.
2. Do not use mobile phones outdoors.
3. The personnel who are struck by lightning shall be rescued by cardiopulmonary resuscitation immediately.
Chinese Academy of SciencesresearcherAcademicians of the International Academy of Astronautics put forward a new generation of lightning protection technology, called "intelligent lightning protection technology", for the first time in the world, by eliminating the danger of lightning strikes, so that the protection targets will not be struck by lightning.The former Space Center of the Chinese Academy of Scienceselectrical scienceA team of experts, after more than ten years of dedicated research and developmentmodel experiment , practical engineering research, field experiments and other aspects and methods of research have proved the rationality and feasibility of this technology.During this period, it was fully affirmed by many expert meetings of various sizes, and was praised as "the dawn of lightning protection in the 21st century".
Statistics
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Lightning frequency——When a thunderstorm is in progress, the thunder rumbles continuously. If the interval between thunder is less than 15 minutes, no matter how long the intermittent propagation time of thunder, it is considered as a thunderstorm;If the pause time of thunder is more than 15 minutes, the front and back are divided into two thunderstorms.
Lightning hour——That is to say, thunderstorms have occurred in this astronomical hour. More generally, thunder has been heard in this time regardless of the duration of thunderstorms.The "annual lightning hours" in a region means how many astronomical hours a year there have been thunderstorms in the region, regardless of whether the thunderstorm lasts for a full hour or only a few minutes in a certain hour.
Number of thunderstorm days - also calledLightning dayNumber.This is what we are most familiar with.As long as thunderstorms have occurred and thunder has been heard on this day, no matter how long the thunderstorm lasts, it will be counted as a lightning day."Annual lightning days" is equal to the sum of annual lightning days.
Thunderstorm months——It is also called the number of lightning months, which means that thunderstorms have occurred in this month."Annual thunderstorm months" refers to the number of thunderstorms in a year.
