Climate Change Impact on India and World – International Reports, Key Observations, etc.

Explained: Occurrence of Lightning

Note4Students

From UPSC perspective, the following things are important :

Prelims level : Lightening and Thunderstorms

Mains level : Disaster management

At least 70 people died in lightning strikes across Uttar Pradesh, Madhya Pradesh and Rajasthan.

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.

Its formation

  • 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:
  1. Inter-cloud
  2. Intra-cloud
  3. Cloud-to-ground
  • 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 and 30,000 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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