The phenomenon of hail formation has been
studied and taken care of throughout the ages, particularly in Europe and the
Middle East, due to the severe damage caused by hail to agricultural crops as
well as public property, buildings, and infrastructure. Church bells rang in
Europe during the Middle Ages to warn of thunderstorms with hail, and cold
clouds were bombarded by cannons to break the hail grains and prevent the
damage they caused.
Meteorology has advanced significantly since
the 19th century, with satellites, remote control techniques, weather
monitoring balloons and modern aircraft. Today, hail control relies on rockets
that inject chemicals into the hail-bearing part of the cloud, causing drops to
freeze and increasing the number of crystallization cores, reducing the size of
each hail pill and causing it to melt before it reaches the ground surface.
The hail is a type of cloud that contains
spherical blocks of ice ranging in diameter from a few millimeters to several
centimeters, some of which are orange-sized or larger. The hail beads are made
up of 1 mm thick transparent ice layers that alternate.
Hail usually falls for a few minutes, forming
a layer several centimeters thick on the ground.
A deposited piece of hail up to 6 cm in diameter,
formed from the docking of several layers of ice
The hail, which resembles rock in structure,
strength, and hardness, forms in the atmosphere from clouds that float like the
breeze. This icy mountain appears to be moving across the ground, which makes
one wonder of how it formed.
According to
the most recent scientific evidence, hail is formed from supercooled water,
which is water that has been cooled below its normal freezing point of 0°C
(32°F) but still remains a liquid. Scientists aren't sure why this happens, but
they know it happens frequently in the upper atmosphere. When super cooled water
comes into contact with something, such as an ice crystal, dust particle, or
raindrop, it will freeze. Hail is associated with high, vertical cumulonimbus
clouds, which are responsible for severe thunderstorms.
Cumulonimbus cloud
Ice particles form from super cooled water
within a cumulonimbus cloud. Gravity pulls the particles to the bottom of the
cloud, but powerful updrafts of air within the clouds force them back up. They
encounter more supercooled water in the upper part of the cloud, which freezes
on the ice particles, adding another layer of ice to them. This occurs on a
regular basis. As a result, the small pieces of ice grow larger and larger,
eventually forming balls of ice or hailstones. The hailstones eventually become
too heavy to be lifted back up to the cloud's top and fall to the ground.
Hailstones have a layered structure, similar
to an onion, due to the way they form. Huge hailstones form in storm clouds
with extremely strong updrafts.
Large hail is defined as hail that is at least
2.5 centimeters (one inch) in diameter by the National Weather Service in the
United States. That is roughly the width of a quarter. This distinction is
significant because hailstones of this size and larger can cause damage to
property, crops, and structures. The speed at which hailstones fall from clouds
is difficult to predict. However, according to one estimate from the National
Severe Storms Laboratory, a baseball-sized hailstone will fall at about 161 kilometers
(100 miles) per hour.[1]
Cumulonimbus
clouds form when the wind drives small clouds to assembly areas, increasing the
size, height, and amount of water vapor in the assembly areas. When two or more
clouds merge, an upward air current emerges between the coherent clouds,
bringing more water vapor from the cloud base, increasing the underlying energy
of condensation and the speed of the rising air current, driving cloud
components to higher altitudes. These currents are much stronger in the centre
of the cloud than at the edges, giving the impression of a fountain or a rebel
volcano.
Cumulonimbus
clouds are classified into groups based on their accumulated cloud density:
evidence suggests that a first-order cumulonimbus cloud produces up to ten
times the expected precipitation, and a second-order cumulonimbus cloud
produces up to 100 times the amount of precipitation expected from a
non-cumulonimbus cloud.
Cumulus (from Latin) means heap or
accumulation; cumulonimbus clouds are named after a dense puffy cloud form with
a flat base and rounded outlines that can be piled up to the height of a
mountain or even higher.
How hail is formed
The
temperature at the top of the cumulonimbus cloud is below freezing and close to
the temperature required for hail formation, which is about (-13 C). This type
of cloud could indeed reach altitudes of more than 10 kilometers from its base
to its peak, making it similar in shape and height to mountains.
The low
temperatures found on the tops of high mountains on Earth are comparable to the
low temperatures found at the tops of cumulonimbus clouds, whose tops are
dominated by ice crystals, similar to how snow adorns the towering mountain
tops.
Cumulonimbus clouds float in the sky,
accumulating hail grains as long as rising air currents can carry them; when
the rising air currents become too weak to carry the cloud components, the
accumulation process ceases, and cloud components, such as heavy rain or hail,
begin to fall directly to the ground. Hail causes significant damage to homes
and crops all over the world. In October 2010, one of the most devastating
hailstorms in US history struck near Phoenix, Arizona. Hailstones up to 7.6
centimeters (three inches) in diameter were reported, causing $2.8 billion in
damage. In June 2010, a storm in South Dakota produced the largest hailstone
ever recovered in the United States. It had a diameter of 20 centimeters (8
inches) and weighed about 0.9 kilograms (two pounds).
Damage to cars as a result of hail.
The upward flow of warm air within the cloud
carries moisture-laden water droplets, while simultaneously, the descending
cold air current from the cloud's top contains ice crystals that will
eventually form hail. When these two air currents collide, friction occurs,
causing negative charges to accumulate on the falling water droplets due to
their weight, while positive charges build up on the rising ice crystals
because of their lighter weight compared to the water droplets. When enough ice
on top and water on the bottom accumulates, it causes a discharge of static
electricity between the negative and positive poles formed, resulting in severe
lightning and thunder that is much stronger than lightning and thunder in other
non-cumulonimbus cloud types.
The Quran describes hail formation in a fascinating way. In Surah an-Nur (The Light), verse 24:43, it says:
“Art thou not aware that it is God who causes the clouds to move onward, then joins them together, then piles them up in masses, until thou can see rain come forth from their midst? And He it is who sends down from the skies, by degrees, mountainous masses [of clouds] charged with hail, striking therewith whomever He wills and averting it from whomever He wills, [the while] the flash of His lightning well-nigh deprives [men of their] sight.”
This verse beautifully captures the process: clouds are driven, joined, and piled up, eventually releasing raindrops. From these clouds, God sends down mountains filled with hail, striking whom He wills. The lightning within these clouds is so intense that it almost blinds the eyes.
In scientific parlance, as said before, hail crystallizes from a delicate pas de deux between super cooled droplets and hailstones. Upon collision, these icy partners freeze in an intimate embrace, liberating latent heat. This clandestine warmth envelops the hailstone’s surface, defying the chill of neighboring ice crystals.
Yet, the drama unfolds further. As hail descends through the celestial theater, it encounters realms of supercooled droplets and frozen constellations. Here, electrons awaken, their charge ignited by cosmic friction. Positively charged particles ascend, borne aloft by unseen currents—a celestial ballet choreographed by forces both ethereal and elemental.
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Hail, National Geographic Society, Earth Science, Meteorology, May 20, 2022.
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