Monday , 21 September 2020

Know about Hail stones


Akkim Diamond Swaroop*, Dr. Hindustan Abdul Ahad, Chakra pani B, Muneer S, Anil Kumar K
Balaji College of Pharmacy, Anantapur, AP, India

Hail is a form of water precipitation that falls from the sky as pellets of ice. It consists of balls or irregular lumps of ice, each of which is referred to as a hailstone. Hailstones on Earth consist mostly of water ice and measure between 5 and 200 mm (0.20 and 7.9 in) in diameter. Hail formation requires environments of strong, upward motion of air with the parent thunderstorm and lowered heights of the freezing level.
Key words: water, super cooling, rain
Hailstones generally fall at higher speeds as they grow in size, though complicating factors such as melting, friction with air, wind and interaction with rain and other hailstones can slow their descent through Earth’s atmosphere. Severe weather warnings are issued for hail when the stones reach a damaging size, as it can cause serious damage to human-made structures and, most commonly, farmers’ crops
Layers of Ice
If the thunderstorm is cold and windy enough, this ice cluster will accumulate layers of ice the way a dipped candle accumulates layers of wax, through a process called accretion. Opaque, whitish layers form when icy droplets trap air bubbles and stick to the cluster. Clear layers have accreted large drops of super cooled water that freeze when they encounter the hailstone. Of course, much larger hailstones can be made when two smaller ones freeze together.
How they form
Hail forms in strong thunderstorm clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing 0°C. The growth rate is maximum when air is near a temperature of -13°C. Rising air will often reach a point in the atmosphere that is below freezing (hence, ice will form). The ice is suspended in the air by the strong updrafts and will later fall back down. This process will occur over and over adding layer upon layer to the hailstone.

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