Published by the government of Zimbabwe
Tichaona Zindoga
24 November 2009
opinion
Harare — IN Zimbabwe the rainy season, which this year has already begun in earnest, does not only bring the prospects of bountiful food harvests -- or lack of them -- when the season ends in three months' time.
The season brings about mystery and death in the form of lightning, a phenomenon that has never been able to shed some of its controversy and popular myths.
Nor will it, any time soon, especially in Zimbabwe where it claims five times more lives than in any other part of the world with an average of around 250 deaths per year.
In scientific terms, lightning "is produced in thunderstorms when liquid and ice particles above the freezing level collide, and build up large electrical fields in the clouds."
"Once these electric fields become large enough," says www.weatherquestions.com, "a giant 'spark' occurs between them, like static electricity, reducing the charge separation.
"The lightning spark can occur between clouds, between the cloud and air, or between the cloud and ground."
An American lightning solutions company says on its website that the favourite lightning impact points are places where the air has maximum conductivity due to ionisation.
These areas include outcrops of metal ore deposits, which generally contain radioactive compounds, such as granite rocks, ferruginous clays, and fissured limestone through which underground water flows.
This means that atmospheric ionisation near the ground plays a major role in the localisation of lightning impact points.
The tropical regions of the earth contain the most vulnerable areas to lightning, the company said.
In Zimbabwe the high lightning activity has been attributed to this radioactivity concept, due to the prevalence of many rocky outcrops which discharge gamma rays, reaching the stratosphere where they ionise air molecules.
Authorities say granite outcrops, along with fumes from numerous kitchen fires in rural areas lend the ground a strong positive charge that sets up a powerful potential difference with the negatively charged cloud bases.
Lightning is said to be able to produce electrical power of 200 million volts and a heat intensity of up to 30 000 degrees celsius, which is more than the heat of the surface of the sun, all in a matter of a split second.
Traditionalists adamantly believe that lightning and thunder are a natural phenomenon at the disposal of the ancestors and witchcraft practitioners mainly for vindictive purposes.
A number of online journals also have acres of space in which they discredit some popular but wrong conceptions about the lightning phenomenon.
Some of these include that:
·If it is not raining the lightning poses no danger; whereas lightning can occur up to 16km from any rainstorm, and is just as dangerous.
·Lightning hits the highest point or tallest object; whereas hundreds of incidents have been recorded involving lightning hitting the trees instead of towers nearby or hitting the ground a short distance from telephone poles or four storey buildings, for example.
This belief is similar to the one that many tall trees surrounding a building will protect the structure from being struck, which experts dismiss saying trees do not protect against lightning.
In fact, says a source, if lightning strikes such trees, there is the possibility of a powerful "ground charge" that can and does travel and that can hit the nested building
Rubber insulation of vehicles protects its occupants from lightning; while 10 000 volts per 2,5cm of lightning is enough to harm the occupants. Metal roof and sides are said to be the real repellent of lightning, which explains why people travelling in convertibles, bicycles, motorcycles, open-shelled recreational vehicles are at risk of being struck.
Lightning does not strike twice; while lightning could hit more than once an example that is given is that of some buildings being hit four times in 10 minutes during one single lightning storm.
All metal attracts lightning, so you must not wear jewellery or carry any metal conductors; while it has been proven that a 16,7km high 24km wide electrical volt cannot be drawn to small articles like jewellery, for example.
Surge protectors will prevent computers from harm during a lightning strike; whereas the surge protector is "insignificant" to the million-voltage lightning bolt although it can protect some problems, but not against the actual strike damage.
It will be noted, though, that against a backdrop of controversy and a swelter of misconceptions and a seemingly endless bank of "facts" about lightning, there a number of measures that an individual, or a household can take to lessen the risk of being struck by lightning.
There are also measures that are handy in the event that someone is struck by lightning.
The Civil Protection Unit in Zimbabwe says during a thunderstorm, people must avoid using umbrellas and must not be the tallest objects wherever they are and if one is caught in a thunderstorm, the best position is to squat, keep one's feet tightly together and keep the head as low as possible while covering the ears with booth hands.
This position, which other experts also recommend over lying flat on the ground, also minimises the risk of one being caught in a "ground charge".
In the late 1980's an expert hired by the University of Zimbabwe, Engineer Marx van Olsen, discovered that the magnetic field, rather than actual strikes accounted for many lightning deaths.
His contestation was that, just like cattle, people who lie down are caught in the ground charge, which increases the voltage that passes into the body.
The distance between hooves of cattle, which act as electrical poles determine how much charge passes through them.
As such if a person lies down, the distance increases hence the more danger. This view reinforces the squatting theory as a better alternative when caught in a thunderstorm
People are advised to keep away from all metal objects and water bodies and taps, as these there conduct electricity and thus capable of causing harm.
It is also dangerous to ride a tractor, donkey or scotch cart.
The American Meteorological Society and the National Lighting Safety Institution. says that although "no place is absolutely safe from a lightning threat" some places are safer than others and advises that during a lightning storm, finding shelter in a substantial building or a motor vehicle (windows closed) or large enclosed structures (substantially constructed buildings) tend to be much safer than smaller or open structures.
It warns against being in or near high places and open fields, isolated trees, unprotected gazebos, rain or picnic shelters, baseball dugouts, communications towers, flagpoles, light poles, bleachers (metal or wood), metal fences, convertibles, golf carts, water (ocean, lakes, swimming pools, rivers, etc.).
The organisations, among other things, advises that all outdoor activities be stopped whenever is seen or thunder heard or it becomes louder and more frequent, noting that high winds, rainfall, and cloud cover often act as precursors to actual cloud-to-ground strikes notifying individuals to take action.
Unfortunately, many lightning casualties are said to occur as a storm approaches, because people ignore these precursors while as many casualties occur after the perceived threat has passed.
It is advisable to wait at least 30 minutes after a lightning storm has passed to resume outdoor activities.
"Generally," says one report, "the lightning threat diminishes with time after the last sound of thunder, but may persist for more than 30 minutes.
When thunderstorms are in the area but not overhead, the lightning threat can exist even when it is sunny and not raining."
In the event of someone being struck by lightning, the administering of first aid to a victim, as well as instantaneous call for medical help, might save life.
Experts say that before one attempt to rescue the victim, it is imperative to make sure that the place is safe because lightning can strike the place again.
Once in a safe place, one can check for pulse of the victim and if there is no pulse, one should start cardiac compressions and provide warmth to the victim.
When the latter becomes conscious, small quantities of warm fluids shall be administered until he or she gets medical attention.
In Zimbabwe there is one simple and cheap but effective device to protect huts and small buildings against lightning called the "lightning conductor", designed by the University of Zimbabwe's Faculty of Engineering and the Zimbabwe Electricity Supply Authority.
It consists of a thread wire being drawn over a homestead between poles and then bringing the same pieces of wire down a pole, tying it to a lump of scrap metal or wire mesh buried deep in the ground.
It is said that when lightning comes it is "attracted" to the wire and conducted deep into the ground, and out of the way of people and property.
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