Hail, also called "hail", is a kind ofWeather phenomenonIt is most common in summer or at the turn of spring and summer.Hail is a hard spherical, conical or irregular shapeSolid precipitation。[8]It is a smallMung bean, soybeans, big like chestnuts and eggsIce granule。
When the surface water is exposed to the sunvaporizationAnd then rose into the airsteamTogether, they condense into cloudsrelative humidity100%, when encounteringcold airThen it will liquefy and condense with the dust in the air to form raindrops (tropical rain) or ice crystals（Mid latitudeRain). When the temperature drops to a certain extent, the water vapor in the air is supersaturated, so it rains.If you encounter cold air and don'tCoagulation concretionWater vapor will condense into ice or snow, which means snow.If the temperature drops sharply, it will form a larger ice mass, that is, hail.
Hail mostly occurs from February to May in the Gregorian calendar when cold and warm air meet fiercely, and may also be strong and persistent in midsummerthunderstormMiddle landing.[7]Every year in Chinadisaster caused by hail。Especially in the mountainous and hilly areas in the north,Qinghai Tibet PlateauIn the east, in the Yungui area, the terrain is complex, the weather is changeable, there are many hailstones, and the victims are heavy, which is very harmful to agriculture.Violent hail damages crops, houses, people are injured and livestock are killed;Extremely large hail is even bigger than pomelo, which will cause death, destroy large areas of farmland and trees, destroy buildings and vehicles, etc.It has strong lethality.Hail disaster is serious in Chinanatural disasterone of.
The strong updraft in the hail cloud carries many large and small water drops and ice crystals, some of which are combined and frozen into largerIce granule, these particles andSupercooled water dropDelivered by updraft towater contentThe accumulation area can become the core of hail, and these initial growth cores of hail have good growth conditions in the water content accumulation area.
Hailstone nucleusEntered by updraftGrowth zoneAfter that, it collides with supercooled water in the area with a large amount of water and a low temperature to form a transparent ice layer, and then goes up into the low temperature area with a small amount of waterIce crystal, snowflakes and a small amount of supercooled water droplets. The hailstone core sticks to them and freezes to form aOpaqueOf ice.
At this time, the hail has grown up, but the updraft there is weak. When it cannot support the growing hail, the hail will fall in the updraft, and continue to grow by combining ice crystals, snowflakes and water drops in the fall. When it falls into a higher temperature area, the supercooled water drops that hit it will form a transparent ice layer.
At this time, if it falls into another stronger updraft zone, the hail will rise again, repeating the above growth process.In this way, the hail will grow one layer transparent and one layer opaque;Due to the difference of growth time, water content and other conditions, the thickness and other characteristics of each layer are also different.Finally, when the updraft cannot support the hail, it falls from the clouds and becomes the hail we see.
When the raindrops in the clouds encounter the violent rising airflow and are taken to the high altitude below 0 ℃, they will melt into small ice beads;When the airflow weakens, the small ice beads fall back;When the updraft with water vapor increases again, the small ice beads rise again and increase;In this way, small ice beads may gradually become hail and finally fall to the ground.
Short term hail falling in the area
1. There must be a quite thick unstable layer in the atmosphere.2、Cumulonimbus cloudIt must be developed to a temperature that can freeze individual large water droplets (generally considered as - 12~- 16 ℃).
4. The vertical thickness of cloud shall not be less than 6-8 km.
5. In cumulonimbus cloudswater contentRich.Generally 3~8g/m3, there is a liquid above the maximum rising speedSupercooled waterCumulative band of.
6. There should be inclined, strong and uneven updraft in the cloud, generally more than 10-20 m/s.
Disaster characteristics
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Main features
Rare hail disaster in history
1. Strong locality, the impact range of each hail is generally tens of meters to several kilometers wideDivisorHundred meters to more than ten kilometers.
2. The duration is short, and the time of a storm or hail is generally only 2~10 minutes, and a few more than 30 minutes.
3. It is significantly affected by the terrain. The more complex the terrain, the more likely hail will occur.
4、Interannual changeLarge. In the same region, it happens several times in a row in some years, and rarely or never in some years.[2]
5. It occurs in a wide range of climates, from subtropical to temperate, but most of them occur in temperate regions.Mainly occurs inMid latitudeIn the mainland, the north is usually more than the south, the mountains are more than the plains, and the inland is more than the coast.This distribution characteristics and large-scalecold airActivities are related to terrain.The areas with severe hail disasters in China include southern Gansu, eastern GansuYinshan MountainsTaihang Mountains and the western part of Sichuan and Yunnan provinces.
6、SeasonalityHail mostly occurs from March to October.During this period,Warm airActive, cold air activity is frequent, and hail is easy to occur.Generally speaking, hail in China mostly occurs in spring, summer and autumn.
7、TimelinessFrom the time of appearance every day, it is the most from the afternoon to the evening, becauseConvectionThe strongest.The duration of hail fall is not long, usually only a few minutes, but also a dozen minutes.[1]
geographical distribution
Hailstones like golf balls
Hail activity is not only related toweather system It is also greatly affected by topography and landform.China has a vast territory, complex terrain and great differences in landforms. In addition, China has the largest plateau in the worldatmospheric circulationIt has also become complicated.Therefore, China's hail weather affects a large area, and hail disasters are widespread.According to relevant dataSpatial patternThrough comparative analysis, we have the following four understandings.
(1) The hail disaster affected a wide area.Although hail disaster is asmall scaleHowever, there are hail disasters in most areas of China, and almost all provinces have more or less records of hail disasters. The number of counties affected is close to half of the number of counties in the country, which fully shows that the distribution of hail disasters is quite extensive.
(2) Distribution of hail disasterDiscretenessStrong.Most of the hail falls in individual counties and districts.
(3) The distribution of hail disasters is obviously localized.Hail disasters often occur in some specific areas, especiallyQinghai Tibet PlateauThe piedmont area to the east andAgricultural regionThis is closely related to the formation conditions of hail disaster.
(4) Overall hail disaster in ChinaDistribution patternThere are more in the middle east and less in the west,space distribution It presents a pattern of one region, two belts and seven centers (Figure 3).One region refers to ChinaYangtze RiverTo the northYanshanThe area to the south of the first line and to the east of the Qinghai Tibet Plateau is a frequent hail disaster area in China;Two banded fingersChina's first stepThe outer hail prone zone (especially the area to the east) and the eastern edge and the area to the east of the second step are the hail prone zones in China;Seven centers refer to several hail disaster prone centers scattered in two hail prone zones:Northeast HighValue areaNorth ChinaHigh value area, Hubei Henan high value area, Nanling high value area, East SichuanWestern HubeiXiangxiHigh value area, Gansu Qinghai east high value areaKashgarAksuHigh value area.
From Regionnatural disastersystem theoryFrom the perspective of understanding, hail disaster is a disaster formed by the interaction of hail disaster pregnant environment, disaster causing factors and disaster affected bodies.Hail and rainstorm are both severe convective weather processes, which are often accompanied by terrain constraints. Therefore, rainstorm and terrain become the main factors of hail disaster pregnant environment.The strength of hail disaster andRegional differentiationFirst of all, it depends on the characteristics of hail fall. From the regional distribution of hail fall in China, the high value area of hail fall shows the characteristics of one zone and two zones: one zone refers to the hail prone area of the Qinghai Tibet Plateau;The two zones refer to the hail belt in the south and the hail belt in the north. The former is mainly distributed at the altitude of 1000~2000 metersYunnan Guizhou Plateau, extending eastward to the western Hunan and Sichuan Hubei borders, the latter extending from the northern part of the Qinghai Tibet PlateauQilian Mountains、Liupan MountainthroughThe Loess PlateauandInner Mongolia Plateauconnect.
Compared with the regional differentiation of hail disasters (hail) in China, the regional differentiation of hail disasters in China has an obvious trend of eastward, southward and westward expansion, with the following three obvious differences: First, from a large region perspective, hail disaster prone areas and hail disaster most frequent areas are totally different. The former is densely populated North China - the middle and lower reaches of the Yangtze River, while the latter is sparsely populatedQinghai Tibet PlateauRegion.Second, there are two frequent hail damage and disaster, but the former is more east than the latter, especially in the eastern part of the formation of north-south hail disaster zone.Third, the multi hail disaster areas are all located in the multi hail belt, and they are distributed in clusters.It can be seen that the regional differentiation of hail disasters in China is deeply influenced by human beingsScope of activitiesThe spatial pattern of the Middle East is more than that of the West.From the comparison of the spatial differentiation of hail and hail disaster in the region, hail is only a natural process, and the change of the nature of the affected body makes the high value area of hail disaster not necessarily the high value area of disaster.Although the affected body is not the direct power to cause the disaster, it makes the hail disaster relatively expand or shrink.
Areas with the most hail in China
The area with the most hail in China isQinghai Tibet Plateau, for exampleTibetHeihe River in the northeast of the autonomous region（Naqu）There are 35.9 days of hail every year on average (53 days in the most years, and 23 days at least);The second isBangor31.4 days, 28.0 days,Ando27.9 days,Suoxian27.6 days, all in the Qinghai Tibet Plateau.
Time distribution
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In general, the hail disaster in ChinaTime distributionIt is very extensive.Although hail falls at any time of the day, there is a relatively concentrated hail fall period in all regions of the country.The analysis of relevant data shows that 70% of hail fall time in most areas of China is concentrated inLocal timeFrom 13:00 to 19:00, the maximum is between 14:00 and 16:00.Western HunanSichuan Basin Hail falls mostly at night in western Hubei, and at noon in some places on the Qinghai Tibet Plateau.In addition, there are obvious monthly changes in hail throughout China, including the monthly changes in atmospheric circulation andmonsoon climateThe characteristics are consistent, and the hail falling area isSouth Branch JetAnd the arrival of hail in various regions is more thanrain beltIt arrived about a month early.
Generally speaking, Fujian, Guangdong, GuangxiHainanTaiwan in March April, Jiangxi, Zhejiang, Jiangsu and Shanghai in March August, Hunan, Guizhou, Yunnan and parts of Xinjiang in April May,Qinling Mountains、Huaihe RiverMost of the regions are from April to August,North ChinaandTibetIn some areas from May to September, Shanxi, ShaanxiNingxiaAnd other regions from June to August, and the vast northern regions from June to July,Qinghai Tibet PlateauIn June to September, it is a hail month (Figure 4).In addition, due to the strong locality of hail, the interannual changes in various regions and even the whole country are very large.
Analysis of the victims of hail disaster in China
ChinaHail disasterBy classifying and analyzing the existing hail cases in China one by one, the research results show that the main types of hail disasters in China are 6 categories and 20 subtypes, of whichgrain cropsThe number of disasters is the largest.From the perspective of dynamic changes, the following four subcategories are worth noting: first, corn, the number of affected crops (compared with other crops) has increased, which is similar to theUniversalityAnd the development of plastic film corn planting.To advance crops through plastic filmGrowth periodUndoubtedly, it has increased the time period of hail disasters.The second is cotton. The number of disasters has increased significantly, especially in some major cotton growing areas.It can be seen that crop varieties and cropsChange in areaIt directly affects the amplification or reduction of disaster.Third, vegetables, fruits and flowers suffered more disastersUrbanization levelThe development of vegetables, melons, fruits, trees and fruits, especially flowers in the urban fringe and the widespread use of greenhouse technology have increased the probability of hail disaster.Visible landcash cropThe change of output directly affects theVulnerabilityDegree.Fourth, the number of communications disasters has increased sharply. With the rapid development of national communications, especially the rise of the network in recent years, the vulnerability of hail victims has increased.
hail
On the evening of April 9, 2016, GuangxiLiuzhou CityLightning and rainstorm occurred in most areas of urban areas and 6 counties,Rongan、MeltwaterHail disaster occurred in some areas of the two counties. The largest hail was as big as eggsAutomobile windshieldBroken.
hail
Main categories
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Hailstones the size of eggs
According to the diameter of most hail (ordinary hail), the cumulative time of hail falling and the thickness of accumulated hail in a hail falling process, the hail is divided into three levels.
1. Light hail: the diameter of most hail does not exceed 0.5 cm, the cumulative hail fall time does not exceed 10 minutes, and the thickness of hail on the ground does not exceed 2 cm.
2. Moderate hail: most hail has a diameter of 0.5~2.0 cm, with a total hail fall time of 10~30 minutes, and a hail thickness of 2~5 cm on the ground.
3. Hail: most hail has a diameter of more than 2.0 cm, a cumulative hail fall time of more than 30 minutes, and a hail thickness of more than 5 cm on the ground.
Hazards
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hail
Hail disasterIs created byStrong convectionweather system Caused bymeteorological disaster Although it appears in a small area and in a short time, it is fierce and intense, and is often accompanied by wind, rainstorm, etcSynoptic process。China is a country where hail disasters occur frequently. Every year, hail brings huge losses to agriculture, construction, communication, power, transportation and people's lives and property.
Many peoplethunderstormHail has been encountered in the weather, usually the maximum value of these hail will not exceedSoftballSize, they fall from the storm clouds.However, sometimes the volume of hail is very large. Once 80 pounds of hail fell from the sky, and when they fell on the ground, they would split into many small pieces.The most mysterious thing is that huge hail falls vertically from the sky when there is no cloud layer in the sky. Many events have confirmed thatAircraft wingScientists are still unable to explain why such huge hailstones occur after being hit by hail.
According to relevant statistics, China's annual economic losses caused by hail amount to hundreds of millions or even billions of yuan.Since the 1980s, with theweather radar、satellite cloud chartReceive, Computer, andCommunication transmissionSuch advanced equipment and a variety of numerical prediction models have been widely used in meteorological operations, greatly improving the ability to track, monitor and forecast hail activities.
Prediction and prevention
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Hail is a kind ofagricultural productionMore harmfulDisastrous weather。When hail occurs, it is often accompanied by strong wind, severe cooling and strong lightning.A hail attack reduced the output of the light ones and cut the harvest of the heavy ones.meteorological observatoryStation basisSynoptic chart、satellite cloud chartAnalysis and radar monitoring can make predictions in advance, but the accuracy is still not very ideal.After long-term observation and practice, people have summarized some common experience in predicting hail.
Popular science of common experience
Sensible heat and cold: If the morning in hail season is cool, the humidity is high, and at noonsolar radiationStrong, causingAir convectionIf it is vigorous, it is easy to develop into cumulonimbus clouds and form hail.Therefore, there are such sayings as "chilly in the morning, head broken in the afternoon" and "heavy dew in the morning, hail fierce in the afternoon".
Identify wind direction: Strong wind often appears before hail, while wind direction changes strongly.Agricultural proverbsThere are such sayings as "evil clouds grow when the wind blows, and hail falls with the wind", "wind twists the clouds, and hail flakes".In addition, if the wind direction turns to northwest or north after the continuous south wind blows, and when the wind increases, hail is often accompanied, so there is a saying of "no east wind, no rain, no south wind, no hail".
Cloud observing stateThere are many proverbs all over the country that describe the precursor of hail from the color of clouds, such as "not afraid of black and black in the clouds, but afraid of red in the clouds, and most afraid of white insects under red and yellow clouds", "black cloud tail, yellow cloud head, hail killed sheep and cattle", because the color of hail is first white at the top and black at the bottom, then red in the middle, forming white, black, and red cloud filaments, and the cloud edge is yellow.fromCloudinessThere are also descriptions of hail precursors, such as "black clouds roll up in the afternoon, wind, rain and hail come together", "black clouds turn over in the dark and hot weather, and Tianhe River roars to prevent hail", which indicate that the air convection was extremely vigorous at that time, and the clouds developed rapidly, like thick smoke rushing upward, and the clouds rolled up and down, and this kind of cloud was very easy to hail.
Listen to the thunder: If the thunder continues, it is likely to hail.This is because the lateral lightning in hail clouds is more than the vertical lightningfrequencyHigh, wide range, thunder and echo from various parts of the lightning are mixed together, so it sounds like a continuous feeling.
Recognize lightningGenerally, the lightning in hail clouds is mostly the lightning between clouds, that is, "lateral lightning", which indicates that the process of hail formation in clouds is very severe.Therefore, there is "vertical flashing and horizontal flashing prevention"disaster caused by hail”The statement of.
Look at thingsThere is a lot of experience in seeing things and measuring hail in various places. For example, there is a saying in Guizhou that "wild geese fly low and hail comes quickly"“Willow leafThere are some proverbs in Shanxi, such as "cattle and sheep don't lie on the beam at noon, but beware of hail in the afternoon", "white pearls come out of the grass, and hail falls steadily".For example, there are proverbs in Guangxi, such as "willow leaves turn over and hail days".It should be noted that the above experience should not be judged based on only one item, but should be comprehensively analyzed and applied.The formation of hail must have the following conditions: The formation of hail requires the following conditions.1. There must be a quite thick unstable layer in the atmosphere.2. Cumulonimbus clouds must develop to a height that can freeze individual large water droplets (generally, the temperature is considered to be - 12~- 16 ℃).3. Strong wind shear is required.4 – The vertical thickness of cloud shall not be less than 6-8 km.5. Cumulonimbus clouds are rich in water.It is generally 3~8 g/m3, and there is an accumulation zone of liquid supercooled water above the maximum rising speed.6. There should be inclined, strong and uneven updraft in the cloud, generally more than 10-20 m/s.Cloud picture 1 before the arrival of hail - hot black clouds rise and hail will fall;Black clouds were smoking and hailstones were on the same day.Cloud picture before hail 2 -- Black and yellow clouds roll over, hail in front of us Cloud picture before hail 3 -- Black and yellow clouds roll over, about to fallIced egg。
Meteorological forecast
Orange hail warning
Since the 1980s, with theweather radar、satellite cloud chartAdvanced equipment such as reception, computer and communication transmission are widely used in meteorological operations, which greatly improves the ability to track and monitor hail activities.localmeteorological observatory(Station) In case of hail weather, immediately report to the meteorological observatory and station that may be affected.Meteorological departments at all levels combine modern meteorological science and technology with long-term accumulated forecasting experience to comprehensively forecast the occurrence, development, intensity, scope and harm of hail, so as toForecast accuracyKeep improving.
In order to transmit the hail warning information to government leaders and the masses at all levels as early as possible, meteorological departments at all levels, through local radio, television stations, telephone, computer service terminals andDisastrous weatherAlarm system and other media release "alarm"“Emergency alarm”So that all sectors of society and the vastmassesTake preventive measures in advance, avoid and reduce disaster losses, and achieve significant social andeconomic performance。
Hail red warning
Preventive measures
China is the world's largesthail suppression One of the earlier countries.Due to the severe hail disaster in China, the hail suppression work has received the attention and support of the government.By 2013, many provinces had established long-term test sites, conducted rigorous tests, and achieved a lot of valuableScientific research achievements。Carry out artificial hail suppression to make it develop in the direction expected by people, so as to reduce disasters.
Common methods of artificial hail suppression are：
hail
(1) Use rockets, anti-aircraft guns or aircraft to directlySilver iodide、Lead iodide、dry iceWait for the catalyst to be sent to the cloud;
(2) Put silver iodide, lead iodide, dry ice and other catalysts on the groundCumulonimbus cloudSend to before formingFree atmosphereLet these substancesHail cloudFrom the insideHail embryoFunction: increase hail embryo and reduce hail;
(3) Fire rockets and anti-aircraft guns at hail clouds on the ground, or fire rockets and bombs at hail clouds on aircraft to destroy the water transport of hail clouds;
(4) Use rockets and anti-aircraft guns toWarm cloudPartial sprinklingCoagulation concretion, make the cloud form precipitation to reduce the moisture in the cloud;Scatter in the cold cloud partIce coreTo inhibit hail embryo growth.
Common methods of agricultural production include:
(1) In hail prone areas, grass and trees are planted to increaseforest coverage, improve the geomorphic environment, destroy the hail cloud conditions, and achieve the purpose of reducing hail disasters;
In November 2014,AustraliaQueenslandBrisbaneAt least 39 people were injured by the strongest storm in the past 30 years, strong wind and hail, planes and helicopters were blown over, a large number of building windows were broken, and as many as 90000 households were cut off, with an estimated loss of 100 million Australian dollars.[1]
On the evening of May 6, 2015,HenanprovinceLuoyangThe city was suddenly hit by hail, accompanied byThunderstorm and galeAccording to the pictures released by netizens, hail is the size of an egg. Due to the "attack" of hail, many car windows parked at the roadside were smashed and the car body was damaged to varying degrees.[3]
In the early morning of June 11, 2015,BeijingcityFangshan DistrictLiulihe TownHail hit the central and eastern regions, causing serious damage to villages, farmland, fruit trees, vegetables, etc.amongLu Village, Beibai, Nanbai, and Shicun suffered serious disastersGrapeIt was almost a dead end. Fortunately, no one was injured.The official micro blog of Fangshan District Government announced that after preliminary understanding of the disaster, relevant departments of Liulihe Town rushed to the affected villages to check the disaster.At present, disastersstatistical work andagricultural insuranceThe accident is in progress.The fruit trees on site are almost extinct.
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March 19-20, 2016, GuangdongShaoguan、QingyuanContinuous encounter in multiple placesHeavy rainfallAnd hail attacks, in which the continuous heavy rainfall in Shaoguan urban area has caused more seriousWaterloggingPhenomenon.The Three Prevention Offices of Shaoguan reported on the evening of the 20th that from 19:00 on the 19th to 9:00 on the 20th, there were 28 stations with the measured rainfall of more than 50mm in the city, and the maximum rainfall during this period occurred atHuangpu Town, Lechang City97.7 mm, and 1 – 3 cm hail appeared locally.Afternoon of the 20thShaoguan Municipal Bureau of Land and Resourcesandmeteorological bureauIt also jointly released geological disaster warning information, and the warning level of geological disasters in several regions is Level 3.[4]
At about 2:00 p.m. on May 15, 2018,ShangluoShangnan CountyThe city and surrounding towns were hit by short-time hail, which lasted for more than 10 minutes, with a maximum diameter of 40mm.Pigeon eggsHailstones of the same size damaged vehicles, trees and agricultural facilities, and flooded streets.The specific disaster situation is still under further statistics.[5]
On June 30, 2019 local time,MexicoHalyscoHundreds of houses were damaged by rare hail.[6]
