Hail is a very serious natural disaster, causing colossal damage every year agriculture. Hail is actually chunks of ice falling from the sky. It is not uncommon for ice floes to reach the size of an egg or even an apple.
Grain harvest, vineyards, orchards can be done in 15 minutes. die due to air bombing large hail. According to the High Mountain Geophysical Institute, just one hailstorm on August 19, 2015 caused about 6 billion rubles in damage to the economy of the North Caucasus.
In the Middle Ages, to prevent the formation of large hailstones, people rang bells and fired cannons in an attempt to sound waves cause an ominous cloud to spill onto the Earth before the hailstones in it reach large sizes. Now they are using modern and reliable methods of penetration into a thundercloud - they are launching anti-hail pyrotechnic shells and rockets.
So what is hail, how is it formed, and what determines the size of hailstones? In summer, the air above the Earth's surface warms up greatly, an upward flow is formed, which can be so strong that it can carry steam to a height of 2.5 km, where the temperature is much below zero, as a result of which water droplets become supercooled, and if they rise even higher (by height of 5 km), ice hailstones begin to form. In the future, hailstones can grow to significant sizes due to the freezing of supercooled drops colliding with them, as well as the freezing of hailstones among themselves.
It is important to note that large hailstones can only appear if there are strong updrafts in the clouds that can keep them from falling to the ground for a long time. When the updraft speed in the cloud is less than 40 km/h, for a long time hailstones will not be held in the cloud - and they fall down quite quickly, without having time to grow, and if they fall from a relatively small height, they can melt, as a result of which showers fall on the ground. The thicker the cloud, the greater the likelihood that hailstones will grow to large sizes and large pieces of ice will fall to the Earth.
The clouds from which hail falls are characterized by a dark gray, ashy color and white, as if tattered, tops. Each cloud consists of several clouds piled on top of each other: the lower one is usually located at a small height above the ground, while the upper one is at an altitude of 5, 6 and even more thousand meters above the earth’s surface. Sometimes the lower cloud stretches out in the form of a funnel, as is typical for the phenomenon of tornadoes. Hail is usually accompanied by a thunderstorm and occurs in thunderstorm whirlwinds (tornadoes, tornadoes) with a strong upward air current. Phenomena such as a tornado, tornado and hail are closely related to each other and to cyclonic activity. Hail storms are sometimes unusually strong.
Most often, hail falls in temperate latitudes. Moreover, it occurs much less frequently over expanses of water (upward air currents occur more often over the earth’s surface than over the sea).
Hail that falls in mountainous areas is the largest and most dangerous. This can be explained by the fact that in hot weather The relief of the earth's surface in the mountains warms up unevenly, very powerful upward currents arise, lifting particles of water vapor to a height of up to 10 km, where the air temperature is below -40 ° C. Large hail flying from this height can reach speeds of 160 km/h and lead to crop destruction, serious damage to buildings, transport, and the death of people and animals.
There are many known catastrophic cases of large hail. So, on April 14, 1986 in Bangladesh in the city of Gopalgandezh, kilogram hailstones fell from the sky. The hail killed 92 people. Even heavier pieces of ice bombed the Indian city of Huderabad in 1939. They weighed at least 3.4 kilograms. Judging by the destruction, the largest hailstorm occurred in China in 1902.
And now some facts about hail and measures to combat it in our country.
In Russia, the North Caucasus and the south are most susceptible to natural disasters, in particular heavy hail. On average in the North Caucasus for the entire summer season hail causes damage in areas of about 300-400 thousand hectares, of which the entire crop is destroyed on an area of 142 thousand hectares.
IN last decades in connection with global warming climate frequency and intensity natural phenomena is increasing in Russia by 6-7% per year, and accordingly, losses from natural Disasters. More than 500 cases are recorded in the country every year. emergency situations, including hail and drought, and tornadoes became more frequent.
In 2016, hail struck the North Caucasus for the first time in May-June. According to the Main Directorate of the Ministry of Emergency Situations, as a result of the disaster in the Stavropol region, damage was caused to more than 900 private households, 70.1 thousand hectares of crops were damaged by hail, of which 17.8 thousand hectares were destroyed. IN North Ossetia hail the size of egg, which took place on June 5, destroyed 369.8 hectares of potato crops, corn for grain, barley, the amount of damage is estimated at 27 million rubles.
One of the methods of protection against large hail is to install protective nets over vegetable and grape plantations, but the nets do not always withstand bombardment by very large and fast hail.
More than fifty years ago, 10 paramilitary hail control services were created in the USSR, including three in the North Caucasus - Krasnodar, North Caucasus and later Stavropol service, which protect an area of 2.65 million hectares in the North Caucasus and South federal districts. According to experts, the protection area needs to be expanded. To create new points of influence, command posts 497 million rubles will be required. and for their maintenance annually - about 150 million rubles. However, according to scientists, protection from hail will provide economic effect about 1.7 billion rubles.
Anti-hail rockets spray a reagent into areas of new growth of hail and hail clouds, which leads to accelerated precipitation and rainfall instead of hail. At the end of the 1950s, the first anti-hail projectile, Elbrus-2, fired from anti-aircraft gun KS-19. Since then, shells and installations have been improved. The most recent development of 2014 is the small-sized anti-hail complex "As-Eliya" consisting of an "As" missile and a 36-barreled automated rocket launcher"Eliya-2" with wireless remote control.
Simply put, hail is a type of atmospheric precipitation falling out in the form of ice particles. Usually hail goes in summer during thunderstorms and showers of fairly large cumulonimbus clouds.
A cloud carrying hail can be recognized even as it approaches. She, as a rule, “sits astride” a black and wide thundercloud. Typically, a hail cloud looks like a tall rock with several sharp peaks. If you look at a cloud through a small telescope or very powerful binoculars, you can observe how strong vertical currents pulsate in it.
The “biography” of the city is reflected in its structure. A large hailstone, cut in half, consists like an onion of several layers of ice. Sometimes hailstones resemble layered cake, where ice and snow alternate. Using such layers, one can calculate how many times a piece of ice traveled from rain clouds to supercooled layers of the atmosphere.
Hail originates at an altitude of more than 5 km, where in summer the temperature does not rise above 15°C. Hail is caused by raindrops that, passing through layers of cold air, rise and then fall, freezing more and more and turning into solid ice balls. Sometimes they fluctuate up and down for quite a long time, becoming covered with an increasingly thick layer of ice and snow and increasing in volume. When a sufficient amount of ice accumulates on a hailstone, its mass becomes so large that the force of rising air currents can no longer cope with it. Then the “fat” hailstones fall to the ground.
They should be distinguished from frost and dew, which are nothing more than condensed moisture,
settled on objects or plants. The phenomenon of fog also occurs due to temperature differences. For example, in the fall it comes from warmer bodies of water. Steam, once in cold air, immediately condenses. But the water suspension, due to its own gravity, cannot rise up and become a cloud, and therefore spreads close to the ground, filling the lowlands and floodplains of rivers. However, here we will talk specifically about precipitation. How does hail differ from similar grains? Find out in this article.
Transitional state?
Even a primary school student will tell you what hail is: something between rain and snow. Droplets of water freeze and turn into pieces of ice - small and large. Falling to the ground, they make a loud noise, as if nuts or pebbles are falling. Hailstones do not melt immediately. Sometimes you can observe how they cover the ground with a carpet several tens of centimeters high. But the icy rain, although it hurts your face, immediately turns into water. Sometimes you can hear the crystal ringing of individual “drops” on the asphalt. But more often this is accompanied by the sounds of regular rain. And the snow grains fall to the ground with a quiet rustle. These sediments also differ in appearance. Hailstones are large and translucent. freezing rain looks like shards of glass. And the grains can be likened to miniature snowballs.
How is snow formed?
To seriously understand the question of what hail is, you simply need to return to the basics of natural history and remember how clouds carrying rain or snow are formed. Moisture evaporates from the surface of the earth. But most often clouds form over seas-oceans, where there is more water. air lifts this vapor upward. On different heights Due to the decrease in air temperature, moisture condenses. But it does not turn into droplets of water, but turns into ice crystals, bypassing the liquid state. If the cloud is small and light, the wind drives it to drier areas, where it melts without giving the earth any precipitation. Dense cannot contain heavy, low-floating clouds. Ice crystals begin to fall. If the air temperature at the surface of the earth is above zero, they melt, turning into raindrops. Well, if it’s below zero outside the window, the crystals grow together, forming snowflakes of a wide variety of shapes and sizes.
This is a completely different type of precipitation. And it appears in completely different clouds. Maybe you remember what clouds threaten us with rain? Dense, dark gray, sometimes even purple... Tall, like swirling towers, they fly in quickly, like a tornado. Unlike rainfall, hailstorms are rarely accompanied by lightning and thunder. But there is always a gusty wind. A hailstone is born in the same way as a snowflake - from an ice crystal. But it is not formed at all in flat clouds that carry snow. Hail is generated by the very shape of the clouds. The tall bulk rises several kilometers into the air. It is clear that there is a temperature difference between the lower and upper edges of such a cloud. The crystals located closer to the ground melt, turning into drops of water (hail never falls in winter). But instead of raining down, powerful updrafts push this moisture upward, where it freezes - this time in the form of a small ball of ice. If the wind movement inside the cloud is weak, small hail falls. But if the air flow is strong, then the melted ball is carried back to the top, where it is overgrown with another ice shell. Sometimes hailstones collide and grow together. Then their shape changes. This is no longer a ball, but a complex conical or pyramidal formation. The more the drop migrates, the larger the hail. Maximum size ice pieces were 150 mm and weighed more than a kilogram.
How to prevent hail
It is clear that falling to the ground at a speed of 150 kilometers per hour, even smaller specimens can cause serious injuries and damage. People have long thought about how to prevent the death of crops and livestock from hail. In the Middle Ages, they discovered a pattern: if you make very loud and sharp sounds, then rain will pour out of the clouds. Therefore, when danger approached, people rang a bell or fired a cannon. Due to the pulsation of the air, the hailstones disintegrated, became smaller and melted before reaching the ground. Nowadays a special projectile containing a silver or lead iodide reagent is shot at a dangerous cloud.
Now that we have learned what hail is, let's figure out what snow pellets are. These are small snow balls, 1-2 mm in diameter. Unlike hail, they are fragile, opaque, white. Essentially, these are fused and compacted snowflakes.
For general development
In modern Russian, the word “grad” has another meaning. This is the name of the jet system volley fire, which replaced the outdated Katyusha. This lethal weapon was developed by A.I. Ganichev and the design bureau of the State Research and Production Enterprise "Splav". Basic complex modified from year to year, giving rise to “Grad-V”, “P”, “1A” and other installations.
Ice floes waking up from a thundercloud on a hot day, sometimes small grains, sometimes weighty blocks, smashing dreams of good harvest, leaving dents on the roofs of cars, and even maiming people and animals. Where does this come from? strange looking sediment?
On a hot day warm air containing water vapor rises to the top, cooling with height, the moisture contained in it condenses, forming a cloud. A cloud containing tiny drops of water can fall in the form of rain. But, sometimes, and usually the day should be really hot, the updraft is so strong that it carries drops of water to such a height that they pass the zero isotherm, where the smallest drops of water become supercooled. In clouds, supercooled drops can occur down to temperatures of minus 40° (this temperature corresponds to an altitude of approximately 8 - 10 km). These drops are very unstable. Smallest particles sand, salt, combustion products and even bacteria, carried away from the surface by the same upward flow, when colliding with supercooled drops, become centers of crystallization of moisture, disturbing the fragile balance - a microscopic piece of ice is formed - a hailstone embryo.
Small particles of ice are present at the top of almost every cumulonimbus cloud. However, when falling to earth's surface such hailstones have time to melt. With the speed of the updraft in a cumulonimbus cloud being about 40 km/h, it will not hold the nucleated hailstones. Falling down from a height of 2.4 - 3.6 km (this is the height of the zero isotherm), they manage to melt, landing in the form of rain.
However, under some conditions, the speed of the updraft in the cloud can reach 300 km/h! Such a flow can throw a hailstone embryo to a height of tens of kilometers. On the way there and back - to the zero temperature mark - the hailstones will have time to grow. The higher the speed of updrafts in a cumulonimbus cloud, the larger the hailstones that form. In this way, hailstones are formed, the diameter of which reaches 8-10 cm, and the weight - up to 450 g. Sometimes in cold regions of the planet, not only rain, but also snowflakes freeze on hailstones. Therefore, hailstones often have a layer of snow on the surface and ice underneath. It takes about a million small supercooled drops to form one raindrop. Hailstones larger than 5 cm in diameter occur in super-cell cumulonimbus clouds, which exhibit very powerful updrafts. air currents. It is supercell thunderstorms that generate tornadoes, heavy rainfall and intense squalls.
When a hailstone forms, it can rise several times on the updraft and fall down. Carefully cutting the hailstone sharp knife, you can see that the matte layers of ice in it alternate in the form of spheres with layers clear ice. By the number of such rings, you can count how many times a hailstone managed to rise to the upper layers of the atmosphere and fall back into the cloud.
People have mastered ways to deal with hail. It has been noticed that a sharp sound prevents hailstones from forming. The Indians also preserved their harvest in this way, continuously threshing into large drums as they approached. thundercloud. Our ancestors used bells for the same purpose. Civilization has provided meteorologists with more effective tools. Shooting from anti-aircraft gun through the clouds, meteorologists with the sound of bursting and flying particles powder charge provoke the formation of drops at a low altitude, and the moisture contained in the air is shed as rain. Another way to produce the same effect is by spraying fine dust from an airplane flying over a thundercloud.
Hail is one of the types of rainfall precipitation, which is distinguished by the following features: solid state of aggregation, spherical, sometimes not quite correct form, diameter from a couple of millimeters to several hundred, alternating layers of pure and cloudy ice in the structure of a hailstone.
Hail precipitation is formed mainly in summer, less often in spring and autumn, in powerful cumulonimbus clouds, which are characterized by vertical extent and dark gray color. This type of precipitation usually occurs during a rainstorm or thunderstorm.
The duration of hail varies from several minutes to half an hour. Most often this process is observed within 5-10 minutes, in in some cases it can last more than an hour. Sometimes hail falls on the ground, forming a layer of several centimeters, but meteorologists have repeatedly recorded cases when this figure was significantly exceeded.
The process of hail formation begins with the formation of clouds. On a warm summer day, well-heated air rushes upward into the atmosphere, and moisture particles in it condense, forming a cloud. At a certain altitude, it overcomes the zero isotherm (an arbitrary line in the atmosphere above which the air temperature drops below zero), after which the moisture droplets in it become supercooled. It is worth noting that in addition to moisture, dust particles, tiny grains of sand, and salts rise into the air. Interacting with moisture, they become the core of a hailstone, since drops of water, enveloping a solid particle, begin to quickly freeze.
On further development events are significantly influenced by the speed at which updrafts move in a cumulonimbus cloud. If it is low and does not reach 40 km/h, the flow power is not enough to raise hailstones further. They fall and reach the ground in the form of rain or very small and soft hail. Stronger currents are capable of lifting nucleated hailstones to a height of up to 9 km, where temperatures can reach -40°C. In this case, the hail becomes covered with new layers of ice and grows in diameter up to several centimeters. The faster the flow moves, the larger the hail particles will be.
When the mass of individual hailstones grows so large that the rising air flow cannot contain it, the process of hail begins. The larger the ice particles, the faster their falling speed. A hailstone, the diameter of which is about 4 cm, flies down at a speed of 100 km/h. It is worth noting that only 30-60% of hail reaches the ground in its entirety; a significant part of it is destroyed by collisions and impacts when falling, turning into small fragments that quickly melt into the air.
Even with such a low rate of hail reaching the ground, it can cause significant damage to agriculture. The most serious consequences after hail damage are observed in the foothills and mountainous area, where the power of the upward flows is quite high.
In the 20th century, meteorologists repeatedly observed abnormal hail events. In 1965, in the Kislovodsk region, the thickness of the layer of fallen hail was 75 cm. In 1959, in Stavropol region hailstones have been recorded since large mass. After weighing individual specimens, data with a weight of 2.2 kilograms was entered into the meteorological journal. In 1939, the most big square agricultural land damaged by hail. Then this type precipitation destroyed 100,000 hectares of crops.
To minimize damage from hail, hail storms are being combated. One of the most popular methods is to fire rockets and projectiles at cumulonimbus clouds that carry a reagent that prevents the formation of hail.
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