Monday, June 24, 2019 | ePaper
Measures Needed Against Thunderstorms
The word "thunder" comes from the Old English word "thunor" and the Proto-Germanic "thunraz" while the word "lightning" comes from the Old English word "lighting" or "lighten." Lightning is an electrical energy while thunder is a sound energy. Both occur at the same time during a thunderstorm, but since light travels faster than sound, lightning is seen first before one can hear the sound of thunder. Lightning is fast and very hot while thunder can usher in heavy rain and strong winds, but lightning is more dangerous and destructive than thunder. Lightning is formed when water and ice particles collide with warm, moist air and build up static energy while thunder is formed by the fast expansion of gases in the electrical charge of lightning.
Koteswaram and Srinivasan (1958) expressed that the Bay of Bengal could provide warm humid air masses from the south. The Himalayan range could spill cold dry air masses from the north. Warm, dry air masses could arrive from central India. It is likely that these different air masses form a dry line, much like which occurs in the southern Plains of the United States. Hossain and Karmakar (1998) emphasized the significance of jet stream and intersecting moist and dry air masses associated with the local severe storm formation.
In Bangladesh, thunderstorms occur in all seasons - pre-monsoon, monsoon and post- monsoon as well, characterized by strong surface wind, generally from 40 to 100 miles per hour, and accompanied by heavy rain and often-destructive hails with thunder and lightning. The frequently occurring thunderstorms are observed during pre-monsoon months, these are known as nor'westers, because they come mostly from northwesterly direction.
Bangladesh is a disaster prone country. Almost every year, the country experiences disasters of one kind or another such as tropical cyclones, storm surges, thunderstorm (TS), coastal erosion, floods, and droughts causing heavy loss of life and property and jeopardizing the development activities. Thunderstorms are responsible for the development and formation of many severe weather phenomena.
Thunderstorms, and the phenomena that occur along with them, pose great hazards to populations and, landscapes. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, and flash flooding caused by heavy precipitation. Stronger thunderstorm cells are capable of producing tornadoes and waterspouts. All thunderstorms produce lightning and are very dangerous. In the world, every year, over 20,000 people are affected by lightning and several thousand succumb to their injuries. Only a few studies have been done on lightning in Bangladesh and those few reveal that the number of lightning incidents in the country is quite high. But there is no study on lightning in Jamalpur and Mymensingh district still now. Media reports on lightning incidents in Bangladesh frequently carry news on incidents where a single lightning flash killing multiple victims (the number may reach even 10-12).
Most of the people, killed by lightning are villagers in rural areas who work in open fields. Most of us tend to look at lightning as a harmful side effect of storms, but in realities, these lightning provide benefits to our planet. These benefits include assisting farmers by helping plants grow. Lightning helps fertilize plants. Our atmosphere consists of approximately 78% nitrogen, but this nitrogen exists in a form that plant life cannot use. Therefore, proper dissemination of knowledge on lightning protection and safety measures, down to village level, is essential to curb the death toll and other hazards to the human beings and livestock.
Lightning injury is a global public health problem representing the leading cause of weather-related death after tornadoes, flash floods and hurricanes. The incidence rates of lightning injury are probably higher than registered since there is no referral and information centre where data are collected and stored. Lightning strikes the earth more than 100 times each second, totaling 8 million times every day. An estimated 50,000 thunderstorms occur each day, causing fires and injuries.
Worldwide, mortality from lightning is estimated at between 0.2 and 1.7 deaths/1,000,000 people, affecting mainly the young and people who work outdoors. Lightning injuries are the highest during the summer months. However, in some countries such as India and Vietnam, lightning mostly occurs during the rainy season. Lightning injuries and related deaths mostly affect individuals who work outside or participate in outdoor recreational activities. Worldwide, men are five times more likely than women to be struck by lightning. The most vulnerable age for lightning injury is estimated to be between 10 and 29 years.
Lightning injuries cause high mortality and significant long-term morbidity. A previous study reports that in Bangladesh, the incidence of lightning fatalities is 0.9 per 1,000,000 people per year, which is higher than in high-income countries. In 2016, the country had a lightning event with several strikes, causing 81 deaths, which is particularly high. However, underreporting of lightning strikes is common, as the majority of lightning occurs in rural areas. People used to seek treatment from the local village doctor, pharmacist or traditional healer rather than seeking health care from government facilities, unless the community health provider failed to manage the injuries. Moreover, only a few cases are reported to the police and government hospital records only have information on those who seek treatment.
Now-a-days, one of the most discussed issues of the country is about the increased number of death from lightning and thunderstorm. According to the Department of Disaster Management (DDM), at least 80 people have been killed by lightning up until just May 13, with more occurring later this year. At least 635 people were killed between 2010 and 2015. (Source: The Daily Star report, published on May 14, 2016). On the other hand, Comprehensive Disaster Management Programme (CDMP) of the Ministry of Disaster Management and Relief of the Government says that a total of 180 people were killed due to thunderstorm (Source: Prothom Alo report, published on September 06, 2016).
Apart from these, lightning killed many in other districts. Earlier, in Bangladesh, thunder was not regarded as a natural disaster. But considering the massive death toll this year, the government has recently announced it as a natural disaster so that if anyone dies from a lighting strike, his/her family will receive 20 thousand taka's from the government. But have we ever thought of the reasons behind such incidents? Is there anything wrong in our climate? When the temperature rises, hot moist air rises upwards-- known as updrafts. At the same time, the cool air sinks downwards, and this is called downdrafts. "The collision of updrafts and downdrafts is commonly known as lightning and thunder.
Other than the rising temperature in the atmosphere, there is another specific reason. In prior times, we had many tall, old trees, most of which have been cut down over the years. As we know, trees are electricity resistant; they can absorb lightning strikes and save us. But due to massive deforestation, we are rapidly losing our forests. Besides, the increased use of metallic devices is one more reason for lightning to reach humans easily, as metals also conduct electricity. Previously, lightning was rarely taken as seriously as it is taken today. But given the rise in the death toll in the past few years, the DDM has added a few steps in its latest amendment of Standing Orders on Disaster (SOD).
In conclusion, it may be said that though Bangladesh is not a large country, the space/time distributions of TS vary greatly. In southern areas, there is a wide variation as to the intense period of TS activity. Since lightning can be monitored easily, and continuously, from ground networks, lightning may become a useful tool for monitoring changes in important climate parameters in the future. The government (through Department of Meteorology) or a relevant private sector that owns region-wide lightning detection system should provide thunderstorm forecasting and lightning information to the concerned community. This should be done in collaboration with mass media, especially audio-visual media such as radio and television. Some thunderstorms can be seen approaching, while others hit without warning. It is important to learn and recognize the danger signs and to plan ahead.
(Dr. Forqan Uddin Ahmed, former Additional Secretary)