Headline : Mapping lightning across India
- For the first time, a report called Mid-Monsoon 2019 Lightning Report has mapped lightning strikes across the country, and the lives they have claimed.
About the report:
- The Mid-Monsoon 2019 Lightning Report has been prepared by Climate Resilient Observing Systems Promotion Council (CROPC), a non-profit organisation that works closely with India Meteorological Department (IMD).
- The report is part of effort to prepare a lightning risk map of India and identify lightning hotspots.
Institutes involved in report preparation:
- The report has been prepared by using IMD’s lightning forecasts including Nowcast, Indian Institute of Tropical Management-Pune’s lightning network data, NRSC, ISRO inputs, other satellite data and ground-based impacts reports received from the active network of Lightning Resilient India Campaign.
- The network includes state governments, NGOs, media, etc.
Key Findings of the report
- During April 2019- July 2019:
- There were about 65 lakh lightning strikes in India, of which about 23 lakh (36 per cent) happened to be cloud-to-ground lightning (the kind that reaches the Earth).
- The other 41 lakh (64 per cent) were in-cloud lightning, which remains confined to the clouds in which it was formed.
- Lightning strikes have caused at least 1,311 deaths in this period in India.
- 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.
How Odisha reduced lightning related fatalities:
- The proactive role of the state has resulted in fewer deaths in Odisha inspite of highest number of lightning strikes.
- The steps taken by the state are as follows:
- After receiving alerts from IMD, state 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.
- The state took proactive measures like changing housing patterns, providing education.
- They planted palm trees, which attract high-voltage electricity.
Role of state governments in identifying lightning hotspots:
- IMD-installed sensors across India have been giving alerts since April 2019.
- State governments should take the data and 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, resulting in high casualties.
- States like Odisha, Karnataka, and Andhra Pradesh are doing this systematically.
Connection between lightning and climate change
- The study found that 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, killing persons in Jharkhand.
Protecting the tribals in some lightning prone regions:
- The Chhotanagpur plateau, which is inhabited by tribals, is the most lightning-prone area. The area is electrostatically and thermodynamically charged, resulting in lightning.
- East Singhbhum has the highest number of lightning strikes compared to any other district in India.
- These areas are predominantly inhabited by tribals who need to be relocated to safer spaces, else their population will go extinct.
- The study stress lightning protection to prevent extinction of tribal communities such as Birhor, Pahadiya
Significance of the Report:
- Between 2,000 and 2,500 people are estimated as killed every year in lightning strikes in the country.
- The report will be significant to create a database that can help develop an early warning system for lightning, spread awareness, and prevent deaths.
In Focus: Lightning
What is Lightning?
- Lightning is a giant spark of electricity in the atmosphere between clouds, the air, or the ground.
- It is a result of the difference in electrical charge between the top and bottom of a cloud.
How is lightning formed?
- 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.
- 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.
- The flash of lightning temporarily equalizes the charged regions in the atmosphere until the opposite charges build up again.
- Lightning can occur between opposite charges within the thunderstorm cloud (intra-cloud lightning) or between opposite charges in the cloud and on the ground (cloud-to-ground lightning).
- Lightning 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 lightning strike Earth?
- Earth is a good conductor of electricity and electrically neutral.
- Being relatively positively charged compared to the middle layer of the cloud, 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.
Why there is greater probability of lightning striking raised objects on the ground, such as trees or buildings.?
- Air 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.
- Thus, when they are sufficiently near the ground, about 80-100 m from the surface, they tend to redirect their course to hit the taller objects.
Note: Thousands of thunderstorms occur over India every year. One thunderstorm can involve more than 100 lightning strikes.
- The prediction is made possible through study and monitoring of the in-cloud lightning strikes.
- It is possible to predict lightening 30-40 minutes in advance before lightning strike heads towards Earth.
Section : Science & Tech