The world's largest hail and other records. Hail, precipitation

Ice floes waking up from a thundercloud on a hot day, sometimes small grains, sometimes heavy blocks, crushing dreams of a good harvest, leaving dents on the roofs of cars, and even maiming people and animals. Where does this strange looking sediment come from?

On a hot day, warm air containing water vapor rises to the top, cooling with altitude, and the moisture it contains condenses, forming a cloud. A cloud containing tiny drops of water can fall in the form of rain. But, sometimes, and usually, the day must 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 supercellular cumulonimbus clouds, which contain very powerful updrafts. 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 the hailstone managed to rise to upper layers 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 crops in this way, continuously threshing into large drums when a thundercloud approached. 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.

Reply from Flush[newbie]
I only know when it happens
WHY DOES HAIL HAPPEN?
Hail is pieces of ice (usually irregular shape) that fall from the atmosphere with or without rain (dry hail). Hail falls primarily in summer from very powerful cumulonimbus clouds and is usually accompanied by thunderstorms. IN hot weather Hailstones can reach the size of a pigeon or even a chicken egg.
The strongest hailstorms have been known since ancient times from chronicles. It happened that not only individual areas, but even entire countries were subject to hail damage. Such phenomena still happen today.
On June 29, 1904, large hail fell in Moscow. The weight of hailstones reached 400 g or more. They had a layered structure (like an onion) and external spines. The hail fell vertically and with such force that the glass of greenhouses and conservatories seemed to be shot through with cannonballs: the edges of the holes formed in the glass turned out to be completely smooth, without cracks. Hailstones made holes up to 6 cm in the soil.
May 11, 1929 heavy hail fell in India. There were hailstones 13 cm in diameter and weighing a kilogram! This is the largest hail ever recorded by meteorology. On the ground, hailstones can freeze into large pieces, which explains the amazing stories about the size of hailstones the size of a horse's head.
The history of the hailstone is reflected in its structure. In a round hailstone cut in half, you can see the alternation of transparent layers with opaque ones. The degree of transparency depends on the speed of freezing: the faster it goes, the less transparent the ice. In the very center of a hailstone, the core is always visible: it looks like a grain of “cereal” that often falls in winter.
The rate at which hailstones freeze depends on the water temperature. Water usually freezes at 0°, but in the atmosphere the situation is different. In the ocean of air, raindrops can remain in a supercooled state at very low temperatures: minus 15-20° and below. But as soon as a supercooled drop collides with an ice crystal, it instantly freezes. This is already the embryo of a future hailstone. It occurs at altitudes of more than 5 km, where even in summer the temperature is below zero. Further growth of hailstones occurs under different conditions. The temperature of a hailstone falling under the influence of its own gravity from the high layers of the cloud is lower than the temperature of the surrounding air, so droplets of water and water vapor from which the cloud consists are deposited on the hailstone. The hailstone will begin to get larger. But for now it is small, and even a moderate rising air flow picks it up and carries it to the upper parts of the cloud, where it is colder. There it cools and when the wind weakens it begins to fall again. The speed of the upward flow either increases or decreases. Therefore, a hailstone, having made a “journey” several times up and down into powerful clouds, can grow to significant sizes. When it becomes so heavy that the updraft can no longer support it, the hailstone will fall to the ground. Sometimes “dry” hail (without rain) falls from the edge of a cloud, where the updrafts have weakened significantly.
So, for the formation of large hail, very strong upward air currents are needed. To maintain a hailstone with a diameter of 1 cm in the air, a vertical flow with a speed of 10 m/sec is required, for a hailstone with a diameter of 5 cm - 20 m/sec, etc. Such stormy flows were discovered in hail clouds by our pilots. Even higher speeds—hurricane speeds—were recorded by movie cameras that filmed the growing cloud tops from the ground.
Scientists have long tried to find means to disperse hail clouds. In the last century, cannons were built to shoot at clouds. They threw out a swirling smoke ring into the heights. It was assumed that vortex movements in the ring could prevent the formation of hail in the cloud. It turned out, however, that, despite the frequent shooting, hail continued to fall from the hail cloud with the same force, since the energy of the vortex rings was negligible. Nowadays, this problem has been fundamentally solved, and mainly through the efforts of Russian scientists.

Hail is a type of storm atmospheric precipitation, which is different the following features: hard physical state, spherical, sometimes not quite regular in shape, diameter from a couple of millimeters to several hundred, alternating layers of pure and muddy 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 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. In the warm summer day Well-heated air rushes upward into the atmosphere, moisture particles in it condense, forming a cloud. On a certain height 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 flow rising air cannot hold 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 foothill and mountainous areas, where the power of rising 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 recorded as 75 cm. In 1959, in Stavropol region hailstones with the largest mass were recorded. After weighing individual specimens, data with a weight of 2.2 kilograms was entered into the meteorological journal. In 1939, the most large area 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.

Hail is one of the most unusual and mysterious atmospheric phenomena. The nature of its occurrence is not fully understood and remains the subject of fierce scientific debate. Does hail happen at night - the answer to this question is of interest to everyone who has never experienced this rare phenomenon in the dark.

Brief information about the city

Hail is atmospheric precipitation in the form of pieces of ice. The shape and size of these deposits can vary greatly:

Diameter from 0.5 to 15 cm;
Weight from several grams to half a kilogram;
The composition can also be very different: several layers of transparent ice, or alternating transparent and opaque layers;
The form is very diverse - up to bizarre formations in the form of “flower buds”, etc.

Hailstones easily stick together, forming large particles the size of a fist. Precipitation of more than 2 cm in diameter is already sufficient to cause major damage to a farm. As soon as hail of this size is expected to fall, a storm warning is issued.

Different states may have different size thresholds: it all depends on the specific agricultural area. For example, for grape plantations, even small hailstones will be enough to destroy the entire crop.

Prerequisites

According to modern ideas about the nature of hail, for its occurrence it is necessary:

Water drops;
Condensation yard;
Rising air currents;
Low temperature.

Similar atmospheric phenomenon is formed in 99% of cases in temperate latitudes over large continental spaces. Most researchers believe that thunderstorm activity is a prerequisite.

In tropical and equatorial zones Hail is a fairly rare occurrence, despite the fact that thunderstorms occur quite often there. This happens because for the formation of ice, it is also necessary that at an altitude of approximately 11 km there is enough low temperature, which does not always happen in warm places globe. Hail occurs there only in mountainous areas.

In addition, the probability of hail becomes vanishingly small as soon as the air temperature drops below -30 °C. Supercooled water droplets in this case are located near and inside snow clouds.

How does hail occur?

The mechanism of formation of this type of precipitation can be described as follows:

An ascending air flow containing a significant number of water droplets encounters a cloud layer of low temperature on its path. It often happens that such an air flow is a strong tornado. A significant part of the cloud should be below the freezing point (0 ° C). The probability of hail formation increases a hundredfold when the air temperature at an altitude of 10 km is about -13 °.
Upon contact with condensation nuclei, pieces of ice are formed. As a result of alternating processes of raising and lowering, hailstones acquire a layered structure (transparent and white levels). If the wind blows in a direction where there are a lot of water droplets, a transparent layer is created. If water vapor blows into an area, the hailstones become covered with a crust of white ice.
When colliding with each other, the ice can stick together and seriously grow in size, forming irregular shapes.
Hail formation may last for at least half an hour. As soon as the wind stops supporting the increasingly heavy thundercloud, hail will begin to fall onto the earth's surface.
After the ice passes past the area with temperatures above 0 ° C, the slow process of melting begins.

Why doesn't there hail at night?

In order for ice particles of such a size to form in the sky that they do not have time to melt when they fall to the ground, sufficiently strong vertical air currents are needed. In turn, for the upward flow to be powerful enough, strong heating of the earth's surface is necessary. That is why, in the vast majority of cases, hail falls in the evening and afternoon hours.

However, nothing prevents it from falling out at night, if there is a thundercloud of sufficient size in the sky. True, at night most people sleep, and small hail may go completely unnoticed. That's why the illusion is created that “freezing rain” only occurs during the day.

As for statistical data, in most cases hail occurs in summer time at approximately 15:00. The possibility of precipitation is quite high until 22:00, after which the probability of this type of precipitation tends to zero.

Observational data from meteorologists

Among the most known cases loss " freezing rain» in the dark:

One of the most powerful overnight hailstorms occurred on June 26, 1998 in the Illinois village of Hazel Crest. Then local agriculture seriously damaged by hailstones measuring 5 cm in diameter that fell around 4 a.m.;
On September 5, 2016, hail fell in the vicinity of Yekaterinburg, damaging local crops;
In the Belarusian city of Dobrush on the night of August 26, 2016, ice floes the size of fists broke car windows;
On the night of September 9, 2007, there was hail in the Stavropol region, which damaged 15 thousand private houses;
On the night of July 1, 1991, Mineral waters An icy downpour struck, not only causing damage to local households, but even damaging 18 aircraft. The average size of the ice was about 2.5 cm, but there were also giant balls the size of a chicken egg.

Many people still don't know if it hails at night. The probability of this phenomenon occurring at night is vanishingly small, but it still exists. Moreover, these rare cases are accompanied by many of the strongest anomalies that cause serious harm to the economy.

Simply put, hail is a type of precipitation that falls in the form of ice particles. Hail usually occurs in the summer during thunderstorms and showers from 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 a layer 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.