In September, the authorities in the eastern state of Odisha said nearly 40,000 lightning strikes had taken place in the state on the second day of the month. The disaster management authorities said extreme thunderstorms and lightning activities (cloud-to-cloud and cloud-to-ground strikes) had killed at least 12 persons and injured another 12. They also reported casualty to livestock. Adil Akhzer explains

What causes lightning?

Lightning is a discharge of an electricity spark from a cloud. A lightning strike happens when the negative charges in the bottom of the cloud get attracted to the positive charges in the ground. It can occur between the opposite charges within the thunderstorm cloud (intra-cloud lightning) or between the opposite charges in the cloud and on the ground (cloud-to-ground lightning).

The US-based National Oceanic and Atmospheric Administration says lightning causes thunder. Energy from a lightning channel heats the air briefly to around 50,000 degrees Fahrenheit, much hotter than the surface of the sun, which causes the air to expand outwards and cool rapidly. The rapid expansion and contraction of the air causes the sound waves, which we call thunder -- which can be heard up to miles from the lightning discharge.

Over the last few years, several reports have revealed that the intensity of the lightning strikes has increased in most of the South Asian countries.

A report prepared by Earth Networks -- which collects and analyzes environmental observations from around the world, released data on the in-cloud, cloud-to-ground and the total lightning strikes in India, Bangladesh, Sri Lanka in 2020.

The 2020 report revealed that around 39.5 million lightning pulses were detected in India and around 3 million in Bangladesh. The island nation of Sri Lanka witnessed almost 14.4 million lightning pulses during the period.

It warned that India was susceptible to extreme amounts of heat and moisture due to the country’s proximity to the equator and the Indian Ocean. These factors contribute to acute thunderstorm weather throughout South Asia, as Bangladesh and Sri Lanka experience similar severe weather patterns.

The network also maintains that there is a need for more weather safety awareness and lightning warning tools to improve safety and effectively reduce the risk for those exposed to lightning.

A report by the Centre for Science and Environment and Down to Earth revealed in 2021 that between April 2020 and March 2021, 18.5 million lightning strikes were recorded in India, which was a 34 per cent increase from the 13.8 million strikes compared to the same period in the previous year.

Not only the lightning strikes, but the damage caused by them has also increased, according to the reports.

The data from the National Crime Records Bureau revealed that in 2021, the lightning strikes had caused 2,880 deaths.

Was the Odisha event unusual?

In early September, the Odisha government said the state had recorded 36,597 cloud-to-cloud strikes and 25,753 cloud-to-ground strikes. A few days later, it however, put the total number of strikes at 39,392 after the data was verified by the Indian Institute of Tropical Meteorology, Pune.

The disaster management authorities say the maximum strikes had occurred in the districts of Khordha (4,852), Cuttack (3,070), Boudh (2,560), Nayagarh (2,454) and Bolangir (2,378).

The lightning strikes are recorded through lightning detection sensors and every time a strike takes place, it is automatically recorded. After the state-wise recorded data is provided to the experts in Odisha, they generate the district-wise data based on the longitude, latitude and timing.

The National Remote Sensing Centre says it has established a network of long-range lightning detection sensors to monitor the lightning occurrences.

Experts say this is not the first time that such a huge number of lightning strikes have taken place in a day. There have been several instances in the past as well where extreme lightning events took place in a short period.
In April 2018, over 36,000 lightning strikes were recorded in southern Andhra Pradesh in 13 hours.  

However, it is highly unusual for the state of Odisha to experience nearly 40,000 lightning strikes in just two hours, said Ravindra Khaiwal, professor of environmental health at the Department of Community Medicine and School of Public Health at the Postgraduate Institute of Medical Education and Research, north India’s premier health institute.

Prof Khaiwal said the lightning strikes typically occur at a much lower frequency, even during the monsoon.

“So, while severe thunderstorms can certainly produce prolific lightning for short periods, the recent event in Odisha stands out as extraordinarily intense and concentrated, given the meteorological records. The atmospheric conditions aligned to generate lightning, unlike anything typically observed even in the storm-prone regions of India,” he said.

He said some key factors which had contributed to the rare lightning event were: The presence of a cyclonic circulation over the Bay of Bengal, allowing for tall, intense thunderclouds capable of prolific lightning production, and the collision of cold and warm air masses, creating atmospheric instability and charge separation ideal for lightning generation.

“The high moisture content and instability in the air fuel strong updrafts that drive lightning-producing charge separation. The shift in the winds and moisture can lead to extreme weather,” he said.

Prof Manoranjan Mishra, a geographer at the Odisha-based Fakir Mohan University, echoed Khaiwal. He said on September 2, when thousands of lightning strikes had taken place in the state, there was increased moisture presence in the atmosphere.

“The suitable temperature was also at a higher level. A depression was created and a trough-like condition had developed in the atmosphere, which pulled all the moisture to the upper atmosphere, leading to the formation of black clouds and the lightning activities,” said Prof Mishra.

He said the lightning strikes had started in the morning and ended by evening, with the peak lightning taking place around afternoon.

“It is still being analysed (why there were so many lightning strikes),” he said.

Is climate change responsible?

In 2014, a US-based study projected an increase in the lightning strikes in the United States due to global warming. Experts said while fully attributing any single event to the climate change was difficult, the extreme lightning event may have been influenced by climate change.

“Specific attribution would require detailed modelling studies,” said Prof Khaiwal.

Experts have in the past said deforestation and pollution contribute to climate change which in turn also leads to an increase in lightning

The way forward

With experts warning that the number of lightning incidents is expected to increase, they are stressing the need to increase the forecasting facilities.

“According to the data, lightning incidents happen and will continue. We will have to prepare for it. There is a need to improve the forecasting models which would help provide timely information to the people and eventually minimize deaths,” said Prof Mishra.

“There is also a need to increase awareness among the people so that they take preventive measures in case of lightning.”

He said lightning killed more people in India as compared to the other parts of the world because people worked outdoors, making them vulnerable.