Learning to live with the powerful and destructive natural phenomena such as lightning, thunderstorm, volcano, earthquake, flood, cyclone, hurricane etc. has been a great challenge for mankind. Inquests have been continuing to recognise and understand these freaks of nature since time immemorial. Acquiring appropriate knowledge is the most powerful tool to mitigate the risks of these natural calamities. Along with the many parts of the world Bangladesh has been frequently experiencing the devastating effects of lightning and thunderstorms in recent years.
According to the Ministry of Disaster Management and Relief lightning strikes killed 2,164 people during 2011 to 2020. The data from ‘Save the Society and Thunderstorm Awareness Forum (SSTAF)’ showed at least 177 people were killed in between March 31 and June 07 in 2021. And from July to 09 Sept/21, 32 people were killed by lightning strikes according to the media reports. Grave concerns have been growing with the continuous destructive effects of lightning strikes.
What is lightning?
Lightning is a natural phenomenon which develops when the upper atmosphere becomes unstable due to the convergence of a warm, solar heated, vertical air column on the cooler upper air mass. It is a huge electrical spark (discharge) that flows from a cloud (called a cumulonimbus or thunderstorm) to the ground, or within and between clouds, or from the cloud to air. This same updraft gives rise to an electric charge separation which ultimately leads to the lightning flash. Lightning may be of different types such as Cloud-to-Ground (CG), Negative Cloud-to-Ground (-CG), Positive Cloud-to-Ground (+CG), Cloud-to-Air (CA), Ground-to-Cloud (GC) and Intra-cloud (IC). According to the form or appearances lightings have been classified as: 1) Ball lightning, 2) Rocket lightning, 3) Pearl-necklace lightning, 4) Ribbon lightning, 5) Forked lightning, 6) Sheet lightning and 7) Streak lightning
How does lightning form?
‘As tiny water droplets form inside a storm cloud, they are propelled towards the top of the cloud by strong internal winds (up draughts) where they turn to ice. Some of the pieces of ice grow into hail, but others remain very small. Some of the hail that forms becomes too heavy to be propelled by the up draughts and so begin to fall back through the cloud, bumping into smaller ice particles as they do so. During these collisions, electrons are transferred to the hail giving the hail a negative charge, while the ice particles that have lost electrons gain a positive charge.
The up draughts continue to carry the ice particles upwards, giving the top of the cloud a positive charge. The hail continues to fall through in the lower part of the cloud, giving it a negative charge. As well as being attracted to the positive charge in the top of the cloud, the surplus of electrons in the cloud base are attracted to positive charge in other clouds and on the ground. If the attraction is strong enough, the electrons will rapidly move towards the positive atoms. The path they make in doing so forms the channel we see during a flash of lightning. As negative charge builds at the base of the cloud, the electrons near the ground's surface are repelled. This leaves the ground and the objects on it with a positive charge. As the attraction between the cloud and the ground grows stronger, electrons shoot down from the cloud cutting through the air at around 270,000 miles per hour.’
‘Thunder is the sound produced by the rapid heating of the air by a lightning flash. The air expands explosively and contracts rapidly, producing sound waves. When lightning strikes, the narrow channel of air through which it travels reaches temperatures of up to 30,000 °C almost instantly. This intense heating causes the air to rapidly expand outward into the cooler air surrounding it creating a rippling shockwave which we hear as a rumbling thunder clap, which can be heard as either a sudden, loud crack or a low, long rumble. The lightning and thunder clap are generated simultaneously but with the speed of light at 299,792,458 m/s and the speed of sound at 340.29 m/s, the thunder is always heard after the lightning is seen.’
The scientists, meteorologists, researchers and professionals have been relentlessly working on the development of safety measures that can save many lives from lightning and thunderstorms. It includes structural as well as non-structural measures (e.g. training on safety measures, campaign on mass awareness, encouraging people planting tall trees etc.). There are some safety measures that we must know and practice them properly at the individual and community level as follows:
a) Individual or personal level: It is very tough to recall the tips of taking effective measures at the time of a lightning strike, so we need to drill ourselves to get familiar with them as follows:
Stay alert: As thunder or lightning approaches:
♦ Monitor local weather conditions with an AM/FM or dedicated weather radio, TV, internet etc.
♦ Recognize the signs of an oncoming thunder and lightning storm: towering clouds with a cauliflower shape, dark skies and distant rumbles of thunder or flashes of lightning.
♦ Do not wait for lightning to strike nearby before taking cover. Lightning can strike as far as 10 miles from the area where it is raining. That's about the distance you can hear thunder. When you see lightning, count the time until you hear thunder. If that time is 30 seconds or less, then it’s dangerous!
♦ Recall the 30-30 lightning safety rule that every 3 seconds of delay between a flash to thunder, equates to a distance of 01 km, so where 30 sec flash-to-thunder time interval, the lightning activity is about 10km away. Now is the time to take shelter: quickly! Get inside a house, if possible, into an all-metal vehicle, or move to a low-lying area. Stay put. Once you’ve heard the last peal of thunder, wait for 30 minutes before leaving your shelter.
♦ Look for a large, enclosed building. That's the best choice.
♦ If you are in a car and it has a hard top, stay inside and keep the windows rolled up.
♦ If you are swimming, fishing or boating and there are clouds, dark skies and distant rumbles of thunder or flashes of lightning, get to shore immediately and seek shelter.
♦ Avoid small sheds and lean-tos or partial shelters, like pavilions.
♦ Stay at least a few feet away from open windows, sinks, toilets, tubs, showers, electric boxes and outlets, and appliances. Lightning can flow through them and "jump" to a person.
♦ Do not shower or take a bath during a thunder or lightning storm.
♦ Avoid using regular, land-line telephones, except in an emergency. If lightning hits the telephone lines, it could flow to the phone. Because they are not connected directly to the building's wiring, cell or cordless phones are safe to use.
♦ Insofar as possible, unplug appliances and electronic equipment, including antenna connections.
If caught outside and unable to reach a safe cover:
♦ If your skin tingles or your hair stands on the end, a lightning strike may be about to happen. Crouch down on the balls of your feet with your feet close together. Keep your hands on your knees and lower your head. Get as low as possible without touching your hands or knees to the ground. DO NOT LIE DOWN!
♦ If you are in a boat and cannot get to shore, crouch down in the middle of the boat. Go below if possible.
♦ If you are on land, find a low spot away from trees, metal fences, pipes, tall or long objects.
♦ If you are in the woods, look for an area of shorter trees. Crouch down away from tree trunks.
There is no danger to anyone helping a person who has been struck by lightning — no electric charge remains. So, lightning victims are safe to touch and need urgent medical attention. Get emergency medical help as soon as possible. Call 999. If more than one person is struck by lightning, treat persons who are unconscious first. They are at greatest risk of cardiac arrest.
♦ A person struck by lightning may appear dead, with no pulse or breath. Prompt, proper first aid could save their lives.
♦ If the person is unresponsive or not breathing, start cardiopulmonary resuscitation (CPR) immediately.
♦ Consider an Automatic External Defibrillator (AED), if one is available
Treat those who are injured but conscious next. Common injuries from being struck by lightning are burns, wounds and broken bones. Loss of hearing or eyesight and other nervous system damage may also occur.
b) Community or organisational level: In accordance with the weather forecast or any sign of approaching thunderstorms we have to make arrangements quickly to inform the people of that area about the imminent lightning. We should make our planning for any outside social gathering, meeting, festivals etc. keeping in mind the risks of lightning and thunderstorms. Children should be kept away from any kind of sports outside. Workers whose jobs involve working outdoors in open spaces, on or near tall objects, or near explosives or conductive materials (e.g. metal) have significant exposure to lightning risks. Worker activities at higher risk for lightning hazards include: Farming and field labour, Logging, Explosives handling or storage, Heavy equipment operation, Roofing, Construction works, Power utility field repair, Steel erection/telecommunications and Airport ground personnel operations. In USA the Occupational Safety and Health Administration (OSHA) and the National Oceanic and Atmospheric Administration (NOAA) provide safety guidelines for employers and workers at outdoor worksites. Bangladesh needs to develop lightning guidelines for outdoor events and lightning action plan for the potential striking period of March to June.
With the advancement of science and technologies many structural measures have been developed to save lives, properties and resources include the following:
a) Lightning detector sensor: It is a device that detects the presence of all forms of lightning including intra-cloud, cloud-to-cloud and cloud-to-ground. It can also warn of the risk of overhead lightning before the first discharge. It provides detection up to 300 miles away with directionality for tracking far off and close by storm movement. Lightning archive files are created automatically and may be played back at a later date. Lightning strikes displayed within milliseconds of detection. It is used for advanced storm tracking to determine path of storm. It provides customisable visual and audio alerts of heavy storm activity or nearby lightning strikes. Eight sensors have been installed in different parts of the country including Dhaka, Chittagong, Tentulia in Panchagarh, Badalgachi in Naogaon, Mymensingh, Sylhet, Khulna's Kayra and Patuakhali to provide forecast at least 10 to 30 minutes before flashes of lightning strike the ground. According to the Met office, lightning sensors machines were purchased from the US under the project ‘Strengthening Weather Observatory at 13 Ports in Bangladesh’.
b) Lightning arrestor: A lightning arrestor is a device used on electric power systems and telecommunication systems to protect the insulation and conductors of the system from the damaging effects of lightning. When potentially dangerous lightning strikes, the arrester activates and diverts the lightning to the ground, where it will disperse harmlessly. The government has taken a step to install poles or lightning arresters in the fields across the country. Many electric poles can be turned into arresters easily. The government of Bangladesh is also focusing on ensuring the installation of lightning arresters in every house to reduce the risk of loss of life, damage and permanent failure of electrical/electronic equipment.
c) Surge arrester or surge absorber: It is used to protect the circuit or electrical equipment from high voltage transient or electrical surges. It protects the installation from inside while lightning arrester protects the equipment from outside. Surge arrester intercepts the surges and sends the extra unwanted energy to the ground, while lightning arrester diverts the energy flow to the ground wire. The surge absorber protects against the high voltage transient from lightning strikes as well as when the system voltage is high without lightning strike.
d) Lightning rod: It is used to capture the lightning charges and connect it with the ground. Lightning rods are installed on the highest point on the structure typically top floor on the building, top end of the transmission tower, top of the chimney etc. It protects the building, equipment etc. from direct lightning strikes. The lightning rods are made up of with the copper or conductor which laid down from the top of the structure to bottom of the ground.
e) Concrete lightning shelters: The government is planning to build concrete lightning shelters in haors, baors, beels as farmers and fishermen are being the worst victims of the lightning strikes. Some shelters have already been built in Gangniupazila.
f) Plantation of Tall trees: Trees attract lightning because they provide a path for lightning to travel from the storm cloud to the earth. They do not prevent or reduce the risk of lightning striking a tree but they do control the path of the lightning after it hits. Electricity seeks the path of least resistance, and the moisture inside a tree is a much better conductor than air. Some studies have shown coconut trees attract lightning as the trees are tall and have moisture that acts as a conducting path for lightning. The govt. of Bangladesh has taken a plantation programme of millions of palm trees across the country (about 2.8 million palm kernels have already been planted).
g) Laser tractor beam technology: Recently it was developed by a team of researchers from Australian National University and University of New South Wales. It is capable of controlling the path and direction of lightning before it strikes. This technology may induce electrical discharge from passing lightning, helping to guide it to safe targets and reduce the risk of loss of lives, damaging resources and catastrophic fires as well.
Acquiring adequate knowledge helps us to learn how to protect ourselves from lightning and thunderstorms. It is wise to be familiar with all the structural and non-structural measures and choose them skilfully for utilising and practising in our daily life. Individual, community, national and international efforts are needed to manage lightning and thunderstorms technically, strategically and economically. We need to intensify our research to improve the existing measures and devise appropriate technologies to harness and utilise the enormous power of this natural phenomenon for the benefit of mankind.
The writer is a former editor, Journal of the Institution of Engineers, Bangladesh