The duration of thunderstorm is usually less than 2 hours, and its life cycle includes cumulus stage, mature stage and dissipating stage[2]。Mature thunderstorms are highly developedCumulonimbus cloud(cumulonimbus cloud), the convection center has strong upward movement, and the surrounding area is sinking movement, which can formDownburstandSquall front[1-2]。
According to the mesoscale circulation structure, thunderstorms can be divided into four categories: single cell thunderstorms, multi cell thunderstormsSquall line(square line) and supercell thunderstorms;According to the trigger mechanism, thunderstorms can be divided intoThermal thunderstorm（thermal thunderstorm）、Frontal thunderstorm(front thunderstorm) andTopographic thunderstorm（orographic thunderstorm）[1-2]。
Thunderstorms bring severe weather changes and may become meteorological disasters.Under certain conditions (such as tropical ocean surface), multiple thunderstorms can converge and develop intoMesoscale convective system(Mesoscale Convective System, MCS)[4]。Dry thunderstorm can passCloud ground dischargecausefire。The record of thunderstorms can be traced back to the early days of human civilization.Ancient China、Ancient RomeAnd ancient American civilizations have myths related to thunderstorms[5]。
Thunderstorms often occur at the turn of spring and summer or in hot summer. When the stratification in the atmosphere is unstable, it is easy to produce strong convection. When the potential difference between clouds and between clouds and the ground reaches a certain degree, discharge will occur. Sometimes thunder rumbles and dazzling lightning strike the sky, often accompanied by strong wind, intermittent rain or hail,Thunderstorm weather is always associated with the development of powerful cumulonimbus clouds.In weather forecast, people often say that strong convective weather such as thunderstorm and gale means thunderstorm weather accompanied by strong wind or hail.[15]
Since the occurrence and development of thunderstorms are linked with cumulonimbus clouds, from the emergence to disappearance of thunderstorm clouds, it has a strong local and sudden nature, with a horizontal range of only a few kilometers or more than ten kilometers, and only 2-3 hours on the time scale, so it is difficult to forecast such a small and medium-sized weather system.[15]
Severe thunderstorm is a kind of disastrous weather. Thunder and lightning can cause lightning and fire danger. Strong wind blows down houses, uproots trees, fruits, trees, vegetables and other crops that are hit by hail and suffer serious losses, even no harvest. Sometimes local rainstorm also causes mountain torrents, mud rock flows and other geological disasters.[15]
Cumulonimbus clouds that form thunderstorms are developing vigorously, and ice crystals are often found in the upper part of the clouds.Glaze attachment of ice crystals, breaking of water drops andAir convectionAnd so on, making the cloud generate electric charge.The distribution of charge in the cloud is very complicated, but in general, the upper part of the cloud ispositive chargeMainly, the middle and lower parts of the cloud are mainly negatively charged, and there is a small area in the strong updraft in front of the lower part of the cloudpositive electricityZone.Therefore, a cloud is formed between the top and bottomPotential differenceWhen the potential difference reaches a certain degree, discharge will occur, which is the lightning phenomenon commonly seen,FlashwayThe sudden increase of temperature in causes the volume of air to expand rapidly, resulting inshock wave, leading to strongThunder。When the cloud layer is very low, sometimes it can formCloud ground dischargeThis is lightning strike.Therefore, thunderstorms are the product of atmospheric instability and the general term of cumulonimbus clouds and their associated strong weather.
The duration of thunderstorms is generally short, and the life history of a single thunderstorm is generally not more than 2 hours.Thunderstorms in China are more in the south than in the north, and more in mountainous areas than in plains.It mostly occurs in summer and autumn, and only in China in wintersouthOccasionally.Thunderstorms usually occur in the afternoon.At night due to cloud topRadiation cooling, make theTemperature stratificationIt becomes unstable and can also cause thunderstorms, calledNight thunderstorm。
Thunderstorm weather
Thunderstorm is a discharge phenomenon in the atmosphere, usually accompanied by showers, sometimes there will be local strong wind, hail and other strong convection weather.Severe thunderstorm weather sometimes brings disasters, such as lightning stroke endangering personal safety, household appliances, computer rooms directly hit by lightning orInduction thunderAnd sometimes cause fire.Lightning is a discharge phenomenon in the atmosphere, which occurs in cumulonimbus clouds. During the formation of cumulonimbus clouds, some cloud clusterspositive chargeSome clouds are negatively charged.Their influence on the earthElectrostatic induction, causing ground or building (structure) surface to produceAnisotropic chargeWhen the charge accumulates to a certain extent, the electric field strength between different charge clouds or between clouds and the earth can break through the air (generally 25-30KV/cm) and start free discharge, which we call“leader discharge ”。The cloud to ground pilot discharge is a gradual leap from cloud to ground. When it reaches the ground (buildings on the ground, overhead transmission lines, etc.), it will generate the main reverse discharge from ground to cloud cluster.In the main discharge stage, due to the intense neutralization of the opposite charges, a large amount ofLightning current(usually tens of kiloamperes to hundreds of kiloamperes), followed by strong lightning and loud noise, which forms lightning.[6]
Thunderstorm weather in Shanghai, lightning over the Oriental Pearl
ThundercloudThe cause of formation or the energy contained in it mainly comes from the movement of the atmosphere. The movement and friction of the air flow and the action of the wind on the clouds make it cutGeomagnetic fieldThe movement of the magnetic induction line makes different charges and charged particles further separate and polarize, and finally forms a thunderstorm with a large amount of charges.Thundercloudelectric fieldWhen the intensity reaches enough, it will cause internal discharge in the thundercloud, or strong discharge between thunderclouds, or discharge of thundercloud to the ground or other objects, namelythunder。
classification
Thunderstorm weather
There are three kinds of thunderstorms, namely single thunderstorm, multi single thunderstorm and super single thunderstorm.
The method to distinguish them is based on the instability of the atmosphere and the relative wind speed at different levels (seewind shear）。
Single thunderstorm
thunderstorm
Single cell storms occur when the atmosphere is unstable, but there is only a small amount or even no wind shear.These thunderstorms are usually relatively short and will not last for more than 1 hour.There are also many opportunities to see such thunderstorms on weekdays, so they are also called array thunderstorms.[7]
Multicell storms
Also known as Multi cell thunderstorms, it is composed of multiple single thunderstorms and is the further development of single thunderstorms.At this time, a gust belt will be formed due to the flow of air flow. This gust belt can last for several miles. If the wind speed increases, the atmospheric pressure increases and the temperature drops, the gust belt will become larger and larger, and will hit a larger area.[7]
supercell thunderstorm
Also known as Super cell storms, they occur when the wind shear is extremely strong and are composed of thunderstorms of various degrees.This kind of thunderstorm is the most destructive, and it is 30% possible to producetornado。[7]
According to different atmospheric and topographic conditions when thunderstorms are formed, thunderstorms are generally divided intoThermal thunderstorm、Frontal thunderstormandTopographic thunderstormThree categories.In addition, some people also classify thunderstorms that occur in winter into one category, called winter thunderstorms.In the south of China, there are also frequent occurrences of so-called drought thunderstorms, also known asDry thunderstorm。[7]
observation
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Thunderstorm day
thunderstormOfcanamountIt is very big. It is emitted by lightning of a few thousandths to ten tenths of a secondelectric energyIt can reach billions to hundreds of billions of watts, and the temperature is 10000~20000 degrees Celsius.Of course, thunderstorms can also benefit mankind. They can bring a lot of rain to the earth;Lightning struck air can produce hundreds of millions of tons of nitrogen fertilizer every year, which can seep into the land with rain.Of course, we must not forget the lethality of thunderstorms.Strength standard is used habitually“Thunderstorm day”That is to say, the intensity of lightning activity in the region is indicated by the number of days in the year when thunder can be heard.
Annual average thunderstorm days in various regions of China
region
Annual average thunderstorm days
Hainan Island and Leizhou Peninsula in Guangdong
More than 100 days
Other areas south of 23 ° N
More than 80 days
South of Yangtze River
More than 40 days
Most areas north of the Yangtze River
15 to 40 days
Northwest China
Less than 15 days
Thunderstorm days represent the frequency of lightning activities in different regions. It refers to the number of days in a year when there is lightning discharge in a region. As long as you hear more than one thunderstorm in a day, you will reach a thunderstorm day T.According to the frequency of lightning activity and the severity of lightning damage, China calls areas with annual average thunderstorm days T~>90 as strong thunderstorm areas, areas with T ≥ 40 are multi thunderstorm areas, areas with 15 ≤ T ≤ 40 are medium thunderstorm areas, and areas with T ≤ 15 are less thunderstorm areas.[8]
Producing area
Thunderstorms can occur anywhere in the world, even at the poles anddesertZone, but usually lowlatitudeIt will occur frequently in places (especially in tropical rainforest areas), and can occur every day.staySubtropicalandthe temperate zoneIn mid latitude regions, thunderstorms usually occur in summer, and sometimes in winter, they are also affected by cold fronts and have short-term thunderstorms.In addition to Uganda and Indonesia, which are the places with the most frequent thunderstorms in the world, thunderstorms with the strongest force will occur in the midwest and southern states of the United States, because these thunderstorms will be associated with hail ortornadoHappened together.At present, only South America has never had thunderstorms in the worldChileIn the northern Atagama Desert, thunderstorms did not occur because the climate was too dry and it was difficult to form rain clouds.
Weather characteristics
Thunderstorm is a common weather phenomenon in summer.It is generated by cumulonimbus clouds with strong convection. Due to the strong development of cumulonimbus clouds, it is often accompanied by lightning, thunder, rainstorm, gale, and sometimes hail, tornado, downburst and other disastrous weather.
Generally, in weather forecast and external service work, people are used to calling thunderstorms accompanied only by thunder, lightning or (and) showers "ordinary thunderstorms" or "weak thunderstorms", while thunderstorms accompanied by heavy rain, gale, hail, tornado and other serious natural disasters are called "strong thunderstorms".
Generally, the intensity of thunderstorms is low, and the duration is relatively short, mostly from a few minutes to an hour, but there are many thunderstorms;Strong thunderstorms are strong and last for a long time, usually tens of minutes to several hours, and some can intermittently last for several hours to several days (such as cold vortex thunderstorms).General thunderstorms and severe thunderstorms are weather systems with strong convection, and the weather phenomena they produce are collectively calledConvective weather。
Strongly developed thunderstorms may bringtornadoAnd cause damage.[9]
influence
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Severe thunderstorm is a kind of disastrous weather. Thunder and lightning can cause lightning and fire danger, strong wind blows down houses, uproots trees, fruits, trees, vegetables and other crops to suffer serious losses after being hit by hail, or even no harvest. Sometimes local rainstorm also causes geological disasters such as flash flood di, mud rock flow and so on.[10]
Impact on flight
Thunderstorms can produce various weather phenomena endangering flight safety, such as strong turbulence, turbulence, ice accretion, lightning stroke (lightning stroke), rainstorm, sometimes accompanied by hail, tornado, downburst andLow level windshear。The dark clouds rolling in the air contain huge energy and have great destructive power.When the aircraft enters the thunderstorm activity area by mistake, the light ones will cause aircraft damage, and the heavy ones will cause aircraft destruction and death.Therefore, thunderstorms are recognized by the world aviation industry and meteorological departments as natural enemies that seriously threaten aviation flight safety.[11]
The updraft and downdraft in thunderstorm clouds pose a serious threat to flight, especially in mature thunderstorm clouds. The strongest updraft can reach 50-60 m/s, which is comparable to the typhoon wind. When flying in thunderstorm areas, the aircraft will encounter serious turbulence, which will make the flight height rise and fall tens of meters to hundreds of meters in a few seconds.In serious cases,Flight instrumentDistortion, difficult or even out of control of aircraft, is one of the most dangerous weather phenomena leading to flight accidents.[9]
Here are some weather phenomena that may accompany thunderstorms and threaten flight safety:
Hail: In the mature stage of thunderstorm clouds, the height is mostly 3000m to 9000m, and then the possibility of encountering hail is the greatest.When encountering hail in flight, due to the high relative speed, the radar cover, wing, horizontal stability and other parts of the aircraft are vulnerable to hail, which makes the aerodynamic performance of the aircraft worse, increases the stall speed, and easily causes flight accidents.[9]
Ice accretion: thunderstorm clouds contain a large number of supercooled water droplets, which is easy to cause aircraft icing, especially in the takeoff and landing phase of the aircraft, which is often slow and difficult to operate. If the aircraft encounters ice accretion during takeoff and landing, it will often lead to flight accidents.Icing often has a great impact on the stall characteristics, takeoff performance, climbing performance, endurance performance, landing performance, engine performance, stability, etc. of aircraft.[9]
Lightning strike: When the aircraft is flying in the thunderstorm area, due to the strong electric field in the protruding parts such as wings and fuselage, the aircraft is struck by lightning.Lightning strikes usually occur in rising and falling stages, near the zero degree isotherm.[12]
Downburst: Downburst is the product of the intense development of thunderstorms. Its horizontal scale is usually 4-40 kilometers. The thunderstorm gale generated can reach more than 18 meters/second, but its life cycle is very short, generally only 10-16 minutes (micro downburst only a few minutes).As downburst (including micro downburst) is accompanied by strong downdraft and thunderstorm gale, it will do great harm to aircraft takeoff and landing. If aircraft encounters downburst during takeoff, improper handling will lead to flight accidents.[9]
1. Stay indoors.People working outdoors should hide in the building.
2. Do not swim or engage in other water sports.Get out of the water and find a place to hide.
3. Avoid using telephones or other appliances with plugs, including computers.
4. Do not touch the antenna, faucet, water pipe, wire mesh or other similar metal devices.
5. Avoid showering with a shower.
6. Do not handle flammable materials contained in open containers.Do not stand on the top of a mountain or near objects with high conductivity.Trees or masts are easy to be struck by lightning and should be kept as far away as possible.After lightning strikes an object, the current will spread through the ground, so don't lie on the ground, especially on wet ground.You should squat down and minimize the area of contact with the ground.
7. Hikers and other outdoor activities should take their radios with them and keep an eye on the latest weather information sent by the meteorological observatory.
8. Pay attention to the possibility of rainstorm at any time. Do not stay in rivers, streams or low-lying areas.
9. Motorists should be aware of strong gusts when driving on expressways or overpasses.
10. Small craft at sea should be careful against strong wind orWaterspouta surprise attack.
11. In case of tornado, hide in a solid building immediately.Keep away from windows, crouch on the ground and protect your head with hands or thick pads.If you are outdoors, keep away from trees, cars or other objects that can be blown up by tornadoes.[13]
Culture
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thunderstorm
Anger of thunder is fierce in both voice and appearance.At the earliest time, human beings were extremely afraid of the earth shaking thunderbolt and the lightning that broke through the sky.Europeans and Americans believed that "thunder and lightning are the fire of God", and ancient China believed in "thunder" and "electricity mother".During the Eastern Han Dynasty,Wang ChongIn (Balance), he first tried to explain the phenomenon of thunder and lightning from a scientific point of view. He asserted that thunder was formed by the heat of the sun stirring the air.
Some people think it is an American scientistLightning arresterIn June 1752, Franklin, the inventor of, ventured to fly a kite into the air with thunder and lightning, and ignited an electric fire to the ground, which proved that thunder and lightning were discharges in nature.But in fact, it has already been proved to be false.Because if Franklin really led thunder and lightning to the ground, he would have been electrocuted dozens or even tens of thousands of times.After all, the current is really large, and kite flying is absolutely not allowed beside the high-voltage line because it can kill people, so the "electric fire" is several (dozens of?) times higher than the current of the high-voltage line.For details, please refer to Rumor Crusher.
world record
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Non tropical thunderstorms with the longest duration:The supercell thunderstorm formed around the rotating updraft called mesocyclone is a strong thunderstorm.Its diameter can reach several kilometers and last for several hours, causing heavy rain, hail and strong wind.About 30% of supercell thunderstorms will cause tornadoes.It often occurs in the Great Plains of the United States, also known as the Tornado Corridor.(Guinness World Records)[14]
