From UPSC perspective, the following things are important :
Prelims level : Lightening
Mains level : Not Much
Central idea: A few states have requested lightning to be declared a natural disaster due to the high number of deaths caused by it in the country.
Why discuss this?
- Around 2,500 people die every year due to lightning.
- Present norms consider cyclones, droughts, earthquakes, fires, floods, tsunamis, hailstorms, landslides, avalanches, cloudbursts, pest attacks, frost, and cold waves as disasters covered under the State Disaster Response Fund.
- Deliberations are necessary as it is a policy issue.
What is lightning?
- Scientifically, lightning is a rapid and massive discharge of electricity in the atmosphere some of which is directed towards earth.
- The discharges are generated in giant moisture-bearing clouds that are 10-12 km tall.
- The base of these clouds typically lie within 1-2 km of the Earth’s surface, while the top is 12-13 km away.
- Temperatures in the top of these clouds are in the range of –35° to –45°C.
- As water vapour moves upward in the cloud, the falling temperature causes it to condense.
- As they move to temperatures below 0°C, the water droplets change into small ice crystals.
- They continue to move up, gathering mass until they are so heavy that they start to fall to Earth.
- This leads to a system in which, simultaneously, smaller ice crystals are moving up and bigger crystals are coming down.
- Collisions follow and trigger the release of electrons, a process that is very similar to the generation of sparks of electricity.
- As the moving free electrons cause more collisions and more electrons, a chain reaction ensues.
- This process results in a situation in which the top layer of the cloud gets positively charged, while the middle layer is negatively charged.
- The electrical potential difference between the two layers is huge, of the order of a billion to 10 billion volts.
- In very little time, a massive current, of the order of 100,000 to a million amperes, starts to flow between the layers.
Types of lightning
- Broadly, there are three forms of lightning:
- It is the cloud-to-ground form of lightning that kills humans, as well as animals and livestock, and can substantially damage property.
- While the Earth is a good conductor of electricity, it is electrically neutral.
- However, in comparison to the middle layer of the cloud, it becomes positively charged.
- As a result, about 15%-20% of the current gets directed towards the Earth as well.
- It is this flow of current that results in damage to life and property on Earth.
How intensely does it strike?
- A typical lightning flash is about 300 million volts and30,000 amps.
- To put it in perspective, household current is 120 volts and 15 amps.
- A flash of lightning is enough to light a 100-watt incandescent bulb for about three months.
Why does lightning kill so many people in India?
- The reason for the high number of deaths is due to people being caught unawares and more than 70% of fatalities happened due to people standing under isolated tall trees.
- About 25 per cent of the people were struck in the open.
- Also, lightning is the direct promulgation of climate change extremities.
Mitigating lightning incidents
- Lightning is not classified as a natural disaster in India.
- But recent efforts have resulted in the setting up of an early warning system that is already saving many lives.
- More than 96% of lightning deaths happen in rural areas.
- As such, most of the mitigation and public awareness programmes need to focus on these communities.
- Lightning protection devices are fairly unsophisticated and low-cost. Yet, their deployment in the rural areas, as of now, is extremely low.
- States are being encouraged to prepare and implement lightning action plans, on the lines of heat action plans.
- An international centre for excellence on lightning research to boost detection and early warning systems is also in the process of being set up.
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