Disasters and Disaster Management – Sendai Framework, Floods, Cyclones, etc.

Explained: Mapping lightning across India

Note4Students

From UPSC perspective, the following things are important :

Prelims level : About the report

Mains level : Lightening mapping and its benefit


  • For the first time, a report has mapped lightning strikes across the country, and the lives they have claimed.

About the report

  • It has been prepared by Climate Resilient Observing Systems Promotion Council (CROPC), a non-profit organisation that works closely with India Meteorological Department (IMD).

What has the report found?

  • Lightning strikes have caused at least 1,311 deaths in the four-month period between April and July this year, according to a first-of-its-kind report on lightning incidents in India.
  • UP accounted for 224 of these deaths, followed by Bihar (170), Odisha (129) and Jharkhand (118).
  • It counted 65.55 lakh lightning strikes in India during this four-month period, of which 23.53 lakh (36 per cent) happened to be cloud-to-ground lightning, the kind that reaches the Earth.
  • The other 41.04 lakh (64 per cent) were in-cloud lightning, which remains confined to the clouds in which it was formed.
  • Odisha recorded over 9 lakh incidents of lightning (both kinds), the maximum for any state but fewer deaths than Uttar Pradesh, which had 3.2 lakh incidents.

Why are these findings important?

  • The report is part of an effort to create a database that can help develop an early warning system for lightning, spread awareness, and prevent deaths.
  • Between 2,000 and 2,500 people are estimated as killed every year in lightning strikes in the country.
  • It is possible to predict, 30-40 minutes in advance, when a lightning strike heads towards Earth.
  • The prediction is made possible through study and monitoring of the in-cloud lightning strikes.
  • Timely dissemination of this information can save several lives.
  • After carrying out a pilot project in 16 states, the IMD has begun providing lightning forecasts and warnings through mobile text messages from this year.
  • However, this is not yet available in all regions, and there isn’t enough awareness as yet on the kinds of action that need to be taken after an alert.

Back2Basics

Lightening

  • Lightning is a very rapid and massive discharge of electricity in the atmosphere. Some of it is directed towards the Earth.
  • It is a result of the difference in electrical charge between the top and bottom of a cloud.
  • The lightning-generating clouds are typically about 10-12 km in height, with their base about 1-2 km from the Earth’s surface. The temperatures at the top range from -35°C to -45°C.

Mechanism of formation

  • As water vapour moves upwards in the cloud, it condenses into water due to decreasing temperatures.
  • A huge amount of heat is generated in the process, pushing the water molecules further up. As they move to temperatures below zero, droplets change into small ice crystals.
  • As they continue upwards, they gather mass, until they become so heavy that they start descending. It leads to a system where smaller ice crystals move upwards while larger ones come down.
  • The resulting collisions trigger release of electrons, in a process very similar to the generation of electric sparks. The moving free electrons cause more collisions and more electrons; a chain reaction is formed.
  • The 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 billions of volts. In little time, a huge current, of the order of lakhs to millions of amperes, starts to flow between the layers.
  • It produces heat, leading to the heating of the air column between the two layers of cloud. It is because of this heat that the air column looks red during lightning.
  • The heated air column expands and produces shock waves that result in thunder sounds.

How does it strike Earth?

  • The Earth is a good conductor of electricity. While electrically neutral, it is relatively positively charged compared to the middle layer of the cloud.
  • As a result, an estimated 20-25 per cent of the current flow gets directed towards the Earth. It is this current flow that results in damage to life and property.
  • Lightning has a greater probability of striking raised objects on the ground, such as trees or buildings.
  • Once they are sufficiently near the ground, about 80-100 m from the surface, they even tend to redirect their course to hit the taller objects.
  • This is because travelling through air, which is a bad conductor of electricity, the electrons try to find a better conductor and also the shortest route to the relatively positively charged Earth’s surface.
  • Thousands of thunderstorms occur over India every year. One thunderstorm can involve more than 100 lightning strikes.
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