Lightning

Lightning

Subject: Geography

Context:

• Climate change may be sparking more lightning across the world, and there is an increasing scientific evidence pointing to the trend.
• At least 30 people were killed in separate incidents of lightning in various parts of the country in the past 24 hours. While Rajasthan reported 18 deaths

Concept:

What is lightning?

• Lightning is an electrical discharge caused by imbalances between storm clouds and the ground, or within the clouds themselves.

Lightning Process

• Lightning is a very rapid and massive discharge of electricity in the atmosphere, some of which is directed towards the Earth’s surface. These discharges are generated in giant moisture-bearing clouds that are 10-12 km tall. The base of these clouds typically lies within 1-2 km of the Earth’s surface, while their top is 12-13 km away. Temperatures towards the top of these clouds are in the range of minus 35 to minus 45 degrees Celsius.
• As water vapour moves upward in the cloud, the falling temperature causes it to condense. Heat is generated in the process, which pushes the molecules of water further up.
• As they move to temperatures below zero degrees celsius, the water droplets change into small ice crystals. They continue to move up, gathering mass — until they are so heavy that they start to fall to Earth.
• This leads to a system in which, simultaneously, smaller ice crystals are moving up and bigger crystals are coming down.
• Collisions follow, and trigger the release of electrons — a process that is very similar to the generation of sparks of electricity. As the moving free electrons cause more collisions and more electrons, a chain reaction ensues.
• This 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 a billion to 10 billion volts. In very little time, a massive current, of the order of 100,000 to a million amperes, starts to flow between the layers.
• An enormous amount of heat is produced, and this leads to the heating of the air column between the two layers of the cloud. This heat gives the air column a reddish appearance during lightning. As the heated air column expands, it produces shock waves that result in thunder.
• While the Earth is a good conductor of electricity, it is electrically neutral. However, in comparison to the middle layer of the cloud, it becomes positively charged. As a result, about 15%-20% of the current gets directed towards the Earth as well. It is this flow of current that results in damage to life and property on Earth.
• There is a greater probability of lightning striking tall objects such as trees, towers or buildings. Once it is about 80-100 m from the surface, lightning tends to change course towards these taller objects.
• This happens because air is a poor conductor of electricity, and electrons that are travelling through air seek both a better conductor and the shortest route to the relatively positively charged Earth’s surface.

Climate change and lightning

The rise in incidences and intenstity of lightning strikes in Brazil could be due to global warming and the growth of major urban centers, a study by the Atmospheric Electricity Group and published in Geophysical Research Letters in 2020.  .

• Coastal areas may be at the highest risk.
• An increase of one degree Celsius would increase the frequency of lightning strikes by 12 per cent, warned California University in a study published 2015.
• lightning was added to the Global Climate Observing System’s list of Essential Climate Variables in 2016
• A majority of evidence on natural time scales showed an increase of lightning with warming, though that is not finally proven, experts concluded in the first meeting of the Glocal Climate Observing System Task Team on Lightning Observations for Climate Applications (TTLOCA),
• Urbanisation, increased population and a warmer climate guarantee an intensification of the human exposure to lightning hazard,
• A research in 1994 predicted a 5-6 per cent increase in lightning strikes per 1°C, with the exact magnitude dependent on the geographical location, season and diurnal cycle

Cloud burst, lightning linked to forest fires

The availability of more moisture over land due to warming, Cloud burst, lightning linked to forest fires

• a link between cloud burst events, which cause sudden heavy rainfall often triggering flash floods, and forest fires.
• the scientists have studied the concentration of cloud condensation nuclei (CCN are tiny droplets or cloud seeds on which water vapour condenses) in different weather conditions in the Central Himalayan region and have found that there is a five times higher concentration of CCN in the atmosphere during forest fires as against during rains.
• This means there is more condensation during fire events, which explains excessive rainfall after forest fire

Status in India

• In 2010, a 10-year study Relationship between Lightning Activity over Peninsular India and Sea Surface Temperature of lightning activity over Peninsular India established a link between cyclonic storms that developed over the Bay of Bengal and weather disturbances over the Arabian Sea during the post monsoon season, to be driving the lightning activity over the coastal and adjoining continental region of the peninsula.
• Death due to Lightening, Bihar >Uttar Pradesh> Madhya Pradesh
• This is an increase of 34 per cent compared to previous year;
• Lightning strikes increased in Punjab >Bihar >Haryana
• The lightning incidents recorded during the period revealed that seasonality of lightning was different for different states.
• States should undertake lightning micro-zonation for the regions depending on their geography to handle the disaster and death risks better,
• More common than is sometimes realised in the urban areas. As a whole, India sees 2,000-2,500 lightning deaths every year on average.
• Occurrences of lightning are not tracked in India, and there is simply not enough data for scientists to work with.

Precautions

• Lightning rarely hits people directly but such strikes are almost always fatal.
• 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.
• It becomes more dangerous if the ground is wet (which it frequently is because of the accompanying rain), or if there is metal or other conducting material on it. Water is a conductor, and many people are struck by lightning while standing in flooded paddy fields.
• The Met office routinely issues warnings for thunderstorms. But this is a very generic advisory, and for locations that are very large in area.
• Predicting a thunderstorm over a pinpointed location is not possible. Nor is it possible to predict the exact time of a likely lightning strike.
• For reasons given above, taking shelter under a tree is dangerous. Lying flat on the ground too, can increase risks. People should move indoors in a storm, indoors, they should avoid touching electrical fittings, wires, metal, and water.

Lightning Resilient India Campaign (LRIC)

Lightning Resilient India Campaign (LRIC) is a joint initiative of Climate Resilient Observing-Systems Promotion Council (CROPC), National Disaster Management Authority, India Meteorological Department (IMD), Union Ministry of Earth Science, World Vision India, UNICEF among others. The campaign aims to reduce the number of deaths to less than 1,200 a year by 2022.