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| Thursday, 18 March 2004 |
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Be aware of Inter Monsoon lightning hazards by K. R. Abhayasingha The election warmth of the country is on the increase and the concern of all the media seem to be reserved for questioning as to how the result of the coming general election is going to be. But people are feeling a little relaxed this time as a difference of pre-election practices of politicians and their supporters is seen. The question of the polythene being used for election decoration and the pasting of posters covering all important sign boards (a great environmental problem) has been responded positively to a great extent. The humble expectation of the majority of the public is to see a positive trend of these environmental friendly practices during the coming 2-3 weeks. On the other hand, the political warmth over the country may have great influence on the people leading to negligence of other timely important matters and problems. This may result in very unfortunate repercussions. Matters related to weather in and around Sri Lanka seem to be the most important in this regard. Rainfalls in catchment areas are usually low during Northeast Monsoon season. Precipitation is obviously affected by the other climate parameters and changes of the climate. Such influences may lead to decrease of the rainfall intensities which will result in very unfortunate situation in providing drinking water and the production of the hydroelectric power. This problem will be still worse when the rainfall expected during the seasons prior to Northeast Monsoon has not fallen. Such a serious and pathetic situation is prevailing in the island now and it is clearly seen that the influence of the election warmth seem to be a barrier faced by the officers concerned in launching precautionary steps. This will definitely result in very bad situation where all of us have to suffer badly. Analysis of past climate data is very important and useful in forecasting and understanding the future natural calamity. We are in the last lap of the Northeast Monsoon and the change to next season, First Inter Monsoon is very close. Usually this transition begins in mid-March and the change will take us to a different rainfall pattern, which will be the thunderstorm type rainfall over many parts. This will be a good news for many as the water problem is concerned but at the same time we should not forget that the lightning associated with the thundershowers in the First Inter Monsoon usually result in unfortunate and hazardous moments. Death of people and animal and also a great property damage are common hazards by lightning. Inter Monsoon thunderstorms are natural phenomenon, which begins usually in end of March, and increases in intensity and the area during the second week of April. The intensity of the convention which leads to development of thunder clouds depend on a number of parameters of which the warmth of the earth surface and the adjoining low level atmosphere is the most important. Since the Northeast Monsoon we experienced this year was comparatively warm and dry, there is a possibility for the First Inter Monsoon conditions to be favourable for producing intense lightning activity, which may take us to a hazardous situation unless we take this as an important matter to be concerned and recall our memories of all the precautionary steps in order to reduce hazards caused by lightning. Lightning activity over Sri Lanka shows peaks during two Inter-monsoon seasons, March-April and October-November. But since thunderstorms develop under any atmospheric conditions that are capable in developing convective clouds, we should be alert in launching precautionary steps to reduce lightning hazards during all seasons. The electric current of a ground lightning flash is about 25,000 Amperes (25,000 A) and the potential difference between a charged cloud and the earth is about 100 million Volts and the energy of a lightning flash is a about 500 million Joules. Information of lightning incidents in Sri Lanka witnesses for over 50 deaths of human beings and damage to property of billions of rupees worth every year. Lightning causes death and damage outdoors and indoors as well. During bad weather conditions with thunderstorms, lightning surges may reach the inside of a building in a number of ways. Lightning caused hazards indoors could be reduced with a number of precautionary measures, which are introduced in order to pass the high current surge of a direct or indirect lightning current to the earth safely. Some of them are. 1) Install good earth for the electric circuit of buildings. 2) Use Power surge diverters Supply lines of power and communication can be interrupted by a gadget called power diverter which is capable in directing high currants intruding a building along supply cables as a result of a lightning flash to the ground without allowing it to come into the interior parts of the building circuit. 3) Installing lightning conductors. Direct hit of a lightning flash to a building is the most dangerous even when the lightning hazards are concerned. Lonely and tall buildings are the most vulnerable to lightning. The lightning conductor is the widely used device for protection of buildings. Other precautionary measure is not to have any conducting connection (like wires) between houses and the close-by trees. The cloth-line wire and the wire used as supports to old and weak trees are two hazardous examples. If thunderstorms are forecast, * Find shelter in a safe place to avoid exposing yourself to the open air. If the time interval between lightning flash and hearing thunder becomes less than 15 seconds, move quickly to a protected location, as there is immediate danger of a lightning strike nearby. * Keep electrical instruments disconnected from the main power supply. * Television antennas should be disconnected from the television sets and the antenna socket should be placed close to the earth outside the house. During a thunderstorms * As far as possible avoid handling/touching electrical instruments like refrigerator, electric iron, metal frame, TV, and radio. * Avoid touching or standing close to tall metal structures, wire fences and metal clothes lines. * Limit the use of telephones when a thunderstorm is overhead. Best advice is not to touch the telephone in such instances. * Try to avoid loitering in open areas like paddy fields, tea estates or playgrounds. Specially avoid working in open air holding metal tools like knife and iron rods. If this cannot be avoided, crouch down, singly, with feet together. Footwear or a layer of any non-absorbing material, such as plastic sheet, will offer some protection against ground currants. * Do not seek shelter under or near isolated tall trees and in high grounds. If the vicinity of a tree cannot be avoided, seek a position just beyond the spread of the foliage. * By sitting down or lying down, reduce the effective height of the body * If in an open boat, keep a low profile. Additional protection is gained by anchoring under relatively high objects such as jetties and bridges, provided that no direct contact is made with them. * Avoid riding horses or bicycles, or riding in any open vehicle such as a tractor. Avoid swimming or wading. As you were directed towards the memory of some precautionary measures towards the reduction of hazards caused by lightning, a few information of some events related to protection against lightning. 1. A book on lightning hazards in Sinhala Akunu Anathuru will be launched on the World Met Day, 23 March 2004. Contents of the book consist of answers to 40 questions asked frequently by us about lightning, its hazards and prevention from lightning hazards. 2. The Postgraduate Institute of Science (PGIS) University of Peradeniya organizes a workshop on 'Protection against Lightning' to be held on the 27th March 2004 (Saturday) at the Auditorium of the PGIS. The presentations of this workshop are focused on the Physics of lightning, lightning - caused death and damages, technical aspects of lightning protection systems (LPS) and standards of LPS. This workshop will be highly beneficial to everybody, in particular, to the engineering and management community of the industrial and construction sector that seek lightning protection, the science community interested in the physics and engineering aspects of lightning protection and the commercial sector who deal with lightning protection equipment. Those interested in participating may contact the Assistant Registrar of Postgraduate Institute of Science (PGIS) at University of Peradeniya (Phone 081 - 2387542 and Fax 081 - 2389026) or Workshop Coordinator K. R. Abhayasingha, Dept of Meteorology. Phone: 011-2682041, 060-2800083, 077-7287587 (The Writer is Deputy Director Department of Meteorology) |
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