Explained: How lightning strikes, and why it kills

Explained: How lightning strikes, and why it kills

In News:

  • At least 30 people were killed in separate incidents of lightning in various parts of the country in the past 24 hours.

What is Lightning?

  • Lightning is a phenomenon where light energy is produced by imbalances between cumulonimbus clouds and the ground, or within the clouds themselves. Most lightning occurs within the clouds.
  • It can turn into a severe natural disaster when it occurs in extreme forms.
  • It is the flash of electricity that has temperature ranging up to 30,000°C or more.
  • It can result in heavy destruction of the tall buildings, towers, objects, etc.

How Lightning occurs?

  • During a storm, colliding particles of rain, ice, or snow inside storm clouds increase the imbalance between storm clouds and the ground, and often negatively charge the lower reaches of storm clouds.

  • Objects on the ground, like steeples, trees, and the Earth itself, become positively charged—creating an imbalance that nature seeks to remedy by passing current between the two charges.
  • Within a thundercloud, many small frozen raindrops collide with each other as they move around in the air. All of those collisions create an electric charge.
  • After a while, the whole cloud fills up with electrical charges. The positive charges or protons form at the top of the cloud and the negative charges or electrons form at the bottom of the cloud.
    • The base of these clouds typically lies within 1-2 km of the Earth’s surface, while their top is 12-13 km away.

  • Since opposites attract, that causes a positive charge to build up on the ground beneath the cloud.
  • The ground’s electrical charge concentrates around anything that sticks up, such as mountains, people, or single trees.
  • The positive charge coming up from these points eventually connects with negative charge reaching down from the clouds, causing lightning.
  • It is this flow of current that results in damage to life and property on Earth.

What is ‘Thunder’?

  • Thunder is the sound made by a flash of lightning.
  • As lightning passes through the air it heats the air quickly. This causes the air to expand rapidly and creates the sound, known as thunder.

Why does Lightning strike tall objects such as trees and buildings?

  • There is a greater probability of lightning striking tall objects such as trees, towers or buildings.
  • This happens because air is a poor conductor of electricity, and electrons that are travelling through air seek a better conductor and the shortest route to the relatively positively charged Earth’s surface.

How does Lightning conductor on tall buildings work?

  • Lightning conductor is a simple device used to protect tall buildings from the lightning.
  • It consists of a long thick copper rod passing through the building to ground. The lower end of the rod is connected to a copper plate buried deeply into the ground.
    • Copper is used because it is a good conductor of electricity.

  • When a negatively charged cloud passes over the building, positive charge will be induced on the pointed conductor.
  • The negative charges that are attracted to the conductor travels down to the earth. Thereby preventing the lightning strike from damaging the building.

How does Lightning kill humans?

  • People are most commonly struck by what are called “ground currents”.
  • The electrical energy, after hitting a large object (such as a tree) on Earth, spreads laterally on the ground for some distance, and people in this area receive electrical shocks.
  • According to the Annual Lightning Report 2020-2021, about 71% of lightning deaths have occurred while standing under a tree.

Impact of Climate Change on Lightning strikes:

  • Rapid degradation of the environment like global warming, deforestation, depletion of water bodies, concretisations, rising pollution and aerosol levels have cumulatively pushed the environment to extremes.
    • Lightning is the direct promulgation of these climatic extremities.

  • Lightning strikes are projected to increase by 25-50% due to changing climate.

Way Forward:

  • Early lightning warning to farmers, cattle grazers, children and people in open areas is key to minimising deaths.
  • Seasonality of lightning is different for different states. States should undertake lightning micro-zonation for geographical region-wise precise handling of the risk.
  • A local lightning safety action plan, like installing lightning conductors, is also needed to prevent deaths.

Key Facts for Prelims:

  • The Indian Meteorological Department (IMD) has set up a lightning forecast system and gives colour-coded warnings for incidents.
  • The forecast system has four colour-coded warnings based on the intensity of an extreme weather event and issues them in the ascending order of greenyelloworange, and red.
  • In July 2020, Ministry of Earth Sciences launched ‘Damini’ mobile application to monitor lightning occurrences all over India. It alerts the users when lightning occurs within 20-40 km range.

 Science & Tech