From direct strike to ground current, how lightning kills and why it is a major killer in India
Lightning Strikes: Described as a 'giant spark of electricity', a bolt of lightning can pack between 100 million to 1 billion volts of energy and 'contains billions of watts'
Scores of lives have been lost across the country in this monsoon season due to lightning strikes with a single incident in Jaipur killing 11 people on Sunday. Every year, India counts hundreds of fatalities due to this phenomenon. Here's what you need to know.
How much power does lightning contain?
According to the Accidental Deaths and Suicides in India 2019 report, lightning strikes accounted for more than a third of all deaths "attributable to the forces of nature" in that year. In fact, the report noted that there was a rise in cases where lightning was a cause of death over 2018.
Described as a "giant spark of electricity", a bolt of lightning can pack between 100 million to 1 billion volts of energy and "contains billions of watts". Not only that, a lightning strike can also heat up the surrounding air to anywhere between 10,000 degrees Celsius to 30,000 degrees Celsius. Simply put, a lightning strike can pack great destructive potential.
How does lightning kill?
The US National Weather Service (NWS) says that people can be hit by lightning in several ways. First is the direct strike. Though it is not so common, it is potentially the most fatal. "A person struck directly by lightning becomes a part of the main lightning discharge channel. Most often, direct strikes occur to victims who are in open areas," NWS says. The heat produced by the lightning can cause burns but it is the amount of electricity that courses through the body that is the greater fear.
Often, it is the people who have taken shelter under trees who fall prey to a lightning strike. The particular phenomenon operating here is the 'side flash', which occurs when "lightning strikes a taller object near the victim and a portion of the current jumps from the taller object to the victim". Side flashes usually occur when the victim is within a foot or two of the object that is hit by lightning. India's first Annual Lightning Report (2019-2020) found that standing under a tree was, in fact, the top cause of lightning deaths in India, accounting for 71 percent of all lightning fatalities while 25 percent of deaths were due to a direct hit with the remaining 4 percent due to indirect exposure.
Ground current is another common way in which lightning strikes claim their victims. NWS says that "anyone outside near a lightning strike is potentially a victim of ground current". Since ground current can cover a large area, NWS says it is what "causes the most lightning deaths and injuries". What happens in these cases is that after lightning hits a tree or any other object, "much of the energy travels outwards from the strike in and along the ground surface". The lightning enters the body at the point closest to the strike and then zips through the cardiovascular and nervous systems before exiting the body at the contact point farthest from the lightning. "The greater the distance between contact points, the greater the potential for death or serious injury," NWS says.
Then there are casualties that can be caused through conduction. As the term suggests, here the accident happens when metal, which does not attract lightning, provides a "path for the lightning to follow". NWS says that "most indoor lightning casualties and some outdoor casualties are due to conduction". There is also another, the not-so-common way in which lightning hits people called "streamers", which develop when the downward moving strike approaches the ground.
How often do lightning strikes occur?
The Annual Lightning Report 2019-2020, for which the Indian Meteorological Department (IMD) too contributed inputs, said that the maximum number of casualties were reported between 25-31 July 2019 and that period also saw more than 4 lakh lightning strikes across India. The report notes that the north-eastern states and the Chota Nagpur Plateau region were lightning hotspots.
According to the accidental deaths in India report, in 2019, India reported a total of 2,876 lightning deaths, up from 2,357 deaths in the previous year. Bihar (400), Madhya Pradesh (400), Jharkhand (334) and Uttar Pradesh (321) were the states with the highest share of lightning casualties in 2019.
What to do when lightning occurs?
According to NWS, there is no safe location outdoors to shelter in when lightning occurs and the best protection is to stay indoors. People should head indoors when they can hear the thunder as that means they are within striking distance of the lightning.
In India, IMD has set up a lightning forecast system and the weather office gives colour-coded warnings for lightning events. There is also a daily lightning forecast while 'nowcasts' are issued for three-hour intervals on the day of high lightning activity.
According to the NWS, there is a one in 1.2 million chance of an individual in the US being struck during a given year while the odds of being stuck in an 80-year span are 1 in 15,300.
Going by the long period average by the IMD, the rainfall over the country as a whole during the second half (August and September) of the season is most likely to be normal or 94 per cent to 106 per cent
Maharashtra braces for more rains, very intense shower spells in Raigad, Ratnagiri districts today evening
IMD has issued yellow alert for Mumbai and Orange alert for some Maharashtra districts - Raigad, Ratnagiri, Pune, Kolhapur, Satara and Chandrapur until Wednesday
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