What is Lightning?

Context:

Recently few States have demanded that “lightning” be declared as a “natural disaster” because deaths caused by it surpass any other disaster in India.

• According to present norms, cyclone, drought, earthquake, fire, flood, tsunami, hailstorm, landslide, avalanche, cloudburst, pest attack, frost and cold waves are considered as disasters that are covered under the State Disaster Response Fund (SDRF), 75% of which is funded by the Centre.

Relevance:

GS I- Geography

Dimensions of the Article:

1. What is Lightning?
2. More about Clouds that generate lightning and how they are formed
3. What happens when lightning strikes Earth’s Surface?
4. Which areas are lightning-prone?
5. How can the effects of lightning strikes be mitigated?

What is Lightning?

• Lightning is a natural ‘electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud’, accompanied by a bright flash and sound, and sometimes thunderstorms.
• In simple words, it is a very rapid and massive discharge of electricity in the atmosphere.
• It happens as a result of the difference in electrical charge between the top and bottom of a cloud, or between 2 clouds or between clouds and the ground.
• Inter cloud or intra cloud (IC) lightning are visible and harmless.
• Cloud to ground (CG) lightning is harmful as the ‘high electric voltage and electric current’ leads to electrocution.

More about Clouds that generate lightning and how they are 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 leading to a chain reaction.
• The process results in a situation in which the top layer of the cloud gets positively charged while the middle layer is negatively charged.
• In little time, a huge current, of the order of lakhs to millions of amperes, starts to flow between the layers.

What happens when lightning strikes Earth’s Surface?

• 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% of the current flow is 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.
• Lightning Conductor is a device used to protect buildings from the effect of lightning. A metallic rod, taller than the building, is installed in the walls of the building during its construction.
• The most lightning activity on Earth is seen on the shore of Lake Maracaibo in Venezuela.

Which areas are lightning-prone?

• A recently released annual report on lightning by the Climate Resilient Observing Systems Promotion Council (CROPC), which works closely with government agencies like the India Meteorological Department, includes a lightning atlas which maps vulnerability at the district level.
• According to the report, Madhya Pradesh has reported the largest number of cloud to ground lighting strikes, followed by Chhatisgarh, Maharashtra, Odisha and West Bengal.
• Other states with high strike rate include Bihar, UP, Karnataka, Jharkhand and Tamil Nadu.
• Lightning is fairly common, though it is not often realised in the urban centres.
• In India, well over one crore lightning strikes have been recorded in recent years. It is only over the last few years that lightning records have begun to be maintained, thanks to the efforts of CROPC and India Meteorological Department.

How can the effects of lightning strikes be mitigated?

• 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.

-Source: Indian Express