UPSC PRELIMS 2020: Mapping lightning

Formation of lightening

Topic: Mapping lightning

 

Topic in Syllabus: Indian Geography

Formation of lightening

Context:

  • 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.
  • Climate Resilient Observing Systems Promotion Council (CROPC), a non-profit organisation that works closely with India
  • Meteorological Department (IMD), has prepared it.
  • 36 per cent of lightening happened to be cloud-to-ground lightning, the kind that reaches the Earth.
  • Remaining were in-cloud lightning, which remains confined to the clouds in which it was formed.
  • Odisha recorded maximum lightening.

 

Importance of the Report:

  • 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.
  • It is possible to predict, 30-40 minutes in advance, when a lightning strike heads towards Earth.
  • The IMD has begun providing lightning forecasts and warnings through mobile text messages from this year.

 

Formation of Lightening:

  • Lightning is a very rapid and massive discharge of electricity in the atmosphere.
  • 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.
  • 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 reach to 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 has a greater probability of striking raised objects on the ground, such as trees or buildings.

 

Role of Government:

  • State governments should take the data from IMD installed sensors, start an emergency response system, and relay the information to the district level.
  • Location-based SMS services is available, but this is not done in many states.

 

Case Study of Odisha:

  • After receiving alerts from IMD, Odisha send pre-fixed messages to the grassroots utilising their network.
  • Vulnerable people have been trained how to respond after hearing the warning siren.
  • Safe shelters were created.
  • Lightning arresters have been installed on many buildings.
  • Mayurbhanj, which saw 152 deaths last year, recorded only 17 this year.
  • The state took proactive measures like changing housing patterns, providing education.
  • They planted palm trees, which attract high-voltage electricity.

Challenges:

  • Engagement with other disasters as it happened in Bihar.
  • Bureaucratic hurdles in disseminating the information as happened in UP.
  • Lack of manpower with State disaster response authority as happened in Jharkhand.
  • Lack of awareness among people even receiving the alert.

Linkage with Climate Change:

  • Areas prone to heatwaves were also prone to lightning.
  • Pollution increases aerosols in the atmosphere, which in turn increases lightning.
  • There have been at least two or three instances of lightning strikes without rainfall.

 

Sample Question:

The expansion of the air sends out

a) Vibrations and Sound waves
b) Sound waves and Shock waves
c) Shock waves and Vibrations
d) Vibrations, Sound waves and Shock waves

Answer: c)