3. What is a hailstorm? How does it occur? Explain. (15 Marks)
ओलावृष्टि क्या है? यह कैसे होता है? समझाएं।
Candidates need to explain the hailstorm and how it occurs.
In the last decade, India has been repeatedly battered by different extreme events like heavy rainfall causing extensive flooding, droughts, unseasonal rainfall, hailstorm etc. The number of extreme events of very heavy rainfall has almost doubled in the country in the last 50 years. Among other extreme events unseasonal rains and hailstorms are mostly observed during pre-monsoon season from March to April in the country. The unseasonal rains and hailstorms have destroyed crops in lakhs of acres of farmland in many states including Himachal Pradesh, Uttar Pradesh, Uttarakhand, Punjab, Haryana, Madhya Pradesh, Gujarat, Rajasthan, Maharashtra and Andhra Pradesh causing huge losses to farmers.
What is a hailstorm?
- Hailstorm is a severe weather phenomenon, which causes extensive damage to crops, property and livestock. It is a thunderstorm that produces ice as precipitation.
- Hailstorms can cause serious damage to aircraft, automobiles, glass-roofed structures, skylights, besides crops, property, people and livestock.
- Hail is solid precipitation made of balls or irregular lumps of ice, each of which is called a hailstone.
- Unlike graupel or snow-ice pellets that are smaller and translucent, hailstones consist mostly of water ice and measure between 5 mm and 15 cm in diameter.
- Any thunderstorm, which produces hail that reaches the ground, is termed a hailstorm.
- In India, hailstorms mostly affect the northeast and western Himalayas, with the maximum strikes in March and April.
Occurrence of hailstorm:
- A hailstone begins as a water droplet that is swept up by an updraft inside of a thundercloud. Inside the cloud, there are a large number of other supercooled water droplets already present.
- These supercooled particles will adhere to the water droplet’s surface, forming layers of ice around it.
- As the water droplet reaches higher elevations within the cloud it comes into contact with more and more supercooled particles.
- This is because it is at the highest parts of the cloud, where the temperature is too low (at least 32 degrees Fahrenheit) for water molecules to remain in either a liquid or gaseous state.
- The hail embryo will grow larger and larger as it reaches higher altitudes in the updraft.
- The hailstone will reach a size and weight where gravity will begin to act on it and pull it down.
- However, this is not necessarily the end of its formation, as it could be pulled into another strong updraft and remain in the upper part of the cloud.
- Hail forms as super-cooled droplets, ice crystals and water freeze upon an embryo hailstone.
- Once hail forms, gravity will bring the hail to the earth’s surface. If the updraft is stronger than the pull of gravity, the hailstone will continue to grow.
- Once the hail reaches a size that the updraft can no longer keep aloft, the hail stone will make its way down.
Though occurrences of hailstorm are unavoidable, need is felt now for its prediction followed by recovery, rescue and remedial measures. There are methods available these days to detect hail-producing thunderstorms using weather satellites and weather radar imagery. Severe weather warnings are issued now for hail when the hail reach a damaging size, as it can cause serious damage to structures, crops and live stocks.