Lightning is a major natural disaster in India. This was demonstrated by a recent report of one hundred-odd people being killed by lightning on one day in Bihar and Uttar Pradesh. The department of geography at Kurukshetra University found in 2015 that 5,259 people die in India every year due to lightning.
When compared with the population, this figure indicates an overall fatality rate of about 0.25 per million people per year. This is astonishingly low considering most of these deaths are in the rural areas, with low levels of literacy and few buildings with lightning protection. The fatalities are higher over West Central India. Maharashtra state had the highest number of 1,512 fatalities per year. It was followed by West Bengal, Uttar Pradesh and Kerala in that order.
One possibility for the apparently low rate of deaths due to lightning is the low level of reporting, especially from rural areas. The actual fatality rate could possibly be higher in many other parts of India, too, with a good fraction of deaths going unreported.
A study1 (submitted to the Ministry of Home Affairs and Kerala’s Department of Revenue) of lightning accidents in Kerala at the Centre for Earth Science Studies (CESS), Thiruvananthapuram, showed that about 72 persons lost their lives and 112 persons were injured by lightning annually on average in Kerala between 1986 and 2001. They used reports in the media and applications for compensation to the village offices during the 15-year period.
(Editor’s note: The author is a scientist formerly with CESS.)
Such a number of deaths were common in the West as well a couple of centuries ago. They were brought down to one-tenth of the original by making people aware of the phenomenon of lightning and the methods to protect oneself and one’s property during lightning activity. Similar awareness campaigns have been conducted in Kerala state as well, and in one of which this author had the good fortune of playing a role.
Lightning is a giant electrical discharge. It forms mainly in thunderstorms – or cumulonimbus clouds – in India. These clouds are formed when very moist warm air rises and creates a cumulus cloud, the white fluffy cloud seen mostly in the winter in bright blue skies. When there is plenty of moisture, these cumulus clouds tend to grow into giant cumulonimbus clouds typified by their ‘anvil’ shape at the top and produce lightning through a process that is not yet clearly understood.
The lightning discharge itself is a complex process that produces voltages of lakhs of volts (remember that the voltage we get in our homes is just 220 V), currents of tens of thousands of amperes (an electric heater takes around 10-15 A), and heats the air to about 30,000º C, which is five times the temperature of the surface of the Sun. It is this sudden heating to such high temperatures that creates what we call thunder, which is essentially a shockwave like what is created when an aircraft flies at supersonic speeds.
The same group that conducted the CESS study also observed that lightning in this region is possibly formed by sea breeze reaching the Western Ghats and being forced to rise, initiating cloud formation.
This conclusion was supported by a smaller density of lightning accidents in the region west of the Palghat Gap, the main mountain pass for crossing the Western Ghats in this region. The scientists explained this being due to the presence of the gap, rather the absence of mountains, there. But lightning is also known to happen during volcanic eruptions and dust storms.
Lightning activity in Kerala and much of the Western coastal region is usually confined to two seasons: the pre-monsoon period from March to May, and the northeast monsoon from October to December.
Apart from quantifying the accidents in the state, the CESS study found that lightning accidents were higher over some regions of the state and lower in others. The group also reported that, unlike in most other regions of the world, many deaths were happening even among people inside buildings. One explanation for such deaths is that lightning strikes a nearby tree and a heavy current flows through the ground on which the building stands, causing a large voltage between two points on the ground within the house, or between a point on the wall and the floor. This meant a person who touches two places in the building with different parts of his body risks a heavy current flowing through the body.
Kerala has a high density of flora, especially trees, which means many buildings are invariably close to trees. The group suggested the installation of a ‘ring conductor’ around the house to prevent such accidents. This could be true of other regions in the country that receive heavy rainfall and hence are heavily vegetated.
The main precautions to be taken depend on whether one is indoors or outdoors. Buildings can be protected with lightning conductors and electrical equipment can be protected using surge protection devices (SPDs). But people need to take precautions, like keeping away from electrical equipment including wired phones, TVs, etc. (if SPDs are not installed), not touching two points separated by a distance on the floor or wall, not opening any water taps, not going to open areas, etc.
Precautions to be taken if outdoors are elaborate – but the most ideal is to get back indoors quickly. A common idea that mobile phones are risky to use during lightning activity is wrong. Mobile and cordless phones are in fact the only phones that are safe to use when there is lightning activity. Awareness campaigns in the states that have high accidents rates are the real answer to this problem.
V. Sasi Kumar is a scientist formerly at the Centre for Earth Science Studies, Thiruvananthapuram.
J Mar Atmos Res 2007; 3(1): 111-7.↩