- A new study finds that air pollution intensifies lightning up to a threshold and then its probability declines under very high pollution levels.
- The research shows regional differences, with northeast India responding to pollution at much lower thresholds than west-central India due to contrasting moisture conditions.
- Aerosol particle size plays a crucial role in lightning formation, with dust, fine industrial particles, and sea salt affecting cloud electrification differently.
- The study authors recommend that integrating air-pollution data into weather models could improve lightning prediction and help reduce fatalities in India.
Lightning is among India’s deadliest natural hazards, accounting for nearly 40% of all natural disaster-related deaths each year, according to the National Crime Records Bureau. While rising temperatures and stronger convection linked to climate change are known to influence lightning activity, a new study points to air pollution as another key factor shaping how lightning forms inside clouds.
The study, published in Journal of Geophysical Research: Atmospheres, examines how aerosols, tiny particles suspended in the air from both human and natural sources, modulate lightning activity across different regions of India. According to the authors, air pollution can both enhance and suppress lightning, depending on pollution levels, particle size, and regional meteorological conditions.
How pollution influences lightning
Subhojit Ghoshal Chowdhury, the lead author of the study, from the Centre for Atmospheric Sciences at the Indian Institute of Technology Delhi, says the relationship between air pollution and lightning is not linear. “Our study shows that air pollution can both increase and decrease lightning, depending on how polluted the air is and what kind of particles are present,” Chowdhury explains.
He notes that when pollution levels increase moderately, lightning activity intensifies. “Tiny pollution particles, or aerosols, act like seeds, creating many small cloud droplets that get lofted high into the atmosphere. There, they freeze into ice crystals and graupel (soft hail), and collisions between these ice particles generate electrical charge; lightning occurs.”
However, Chowdhury adds that this process reverses when pollution becomes excessive. “When pollution becomes too high, excess particles disrupt the cloud’s internal balance, weaken upward air currents, and reduce the efficiency of ice–graupel collisions. As a result, the cloud becomes less effective at producing lightning, even though it contains more particles.”
“In short, pollution does not increase lightning endlessly,” he says. “Instead, there is a threshold: lightning intensifies up to a point, and beyond that, very polluted air can actually suppress lightning formation inside clouds.”
Chowdhury explains that this increase and then suppression occurs because aerosols fundamentally change how clouds grow and evolve. “Air pollution changes how clouds behave, and the response is not linear,” he says.
At low to moderate pollution levels, aerosol particles help clouds form many small droplets. At very high pollution levels, however, too many droplets compete for available moisture.
“The tipping point depends on local weather conditions, especially temperature and humidity,” he says.
In this study, the threshold occurred at lower pollution levels in northeast India than in west-central India, indicating that regional meteorology plays a crucial role.
Why different regions respond differently
The study compares lightning responses in west-central India and northeast India to understand why pollution affects lightning in these regions differently.
Chowdhury says the contrast highlights the importance of prevailing atmospheric conditions in the regions. Northeast India already has moisture-rich air which helps deep, intense thunderstorms form, he explains. “So, even moderate levels of pollution can enhance cloud growth and lightning, after which the effect quickly saturates.”
West-central India is typically much drier, which is generally less favourable for storm formation, Chowdhury says. So, compared to the northeast, pollution levels need to be higher for clouds to be deep enough to produce strong lightning activity.
According to him, this contrast shows that moisture availability and background climate strongly control how lightning responds to pollution, explaining why similar pollution levels can produce very different outcomes across regions.
Why particle size matters
Beyond pollution levels, the study also examines how aerosol particle size influences lightning formation.
“The size of pollution particles matters because it determines how they interact with clouds and ice inside thunderstorms,” Chowdhury explains.
Smaller particles, mainly from vehicle emissions and industrial pollution, create many tiny cloud droplets. This delays rainfall, allows clouds to grow taller, and can initially increase lightning activity. Larger particles, such as dust and sea salt, play a different role. “They help form ice and graupel, the key ingredients for electrical charging inside clouds, and can strongly enhance lightning activity,” he says.
The study identifies clear regional differences. In west-central India, a largely dusty and arid region, lightning activity peaks when particle sizes are around 10 micrometres. In northeast India, which is dominated by finer aerosols and higher moisture, the strongest lightning occurs at larger particle sizes of around 20 micrometres.
However, Chowdhury notes that when particles become too large, cloud droplets and ice grow too quickly and fall out of the cloud. “This reduces collisions inside the storm and ultimately weakens lightning activity,” he says.
In India, the most relevant aerosol types include fine particles from vehicles, industries, and biomass burning; mineral dust transported from arid regions, especially during the pre-monsoon season; and sea-salt aerosols near coastal regions.
How aerosol effects on lightning shift
Jayanarayanan Kuttippurath, a leading climate scientist at the Indian Institute of Technology Kharagpur, who was not involved in the study, assessed the study’s conclusions, acknowledging that it is “fairly robust” and “makes physical sense,” as aerosols are known to affect cloud ice and storm strength in complex ways. He notes, however, that “the exact point where aerosols switch from enhancing to suppressing lightning depends on how well the model represents cloud microphysics, aerosol size and properties, and lightning processes.”
According to Kuttippurath, “these thresholds may shift under different conditions or in real-world storms,” a reminder that model-based findings may have limited applicability outside controlled settings.
On the differences between northeast and west-central India, Kuttippurath agreed with the study’s view that “background meteorological conditions play a major role” in shaping regional responses. Factors like moisture availability, atmospheric instability, and convection largely determine how responsive storms are to aerosols. He added that “aerosols act more as a modifier of existing storm environments rather than the main driver of lightning activity.”
Kuttippurath also provided a real-world caveat regarding the study’s potential impact on lightning prediction. “It is challenging to include aerosol effects because real-time pollution data are limited and unevenly distributed across India.” He further noted that “there are also technical and computational hurdles in bringing aerosol-aware models into routine operational weather forecasting.”
Implications for forecasting and public safety
Chowdhury stresses that lightning should be treated as a major and growing climate risk in India. “Lightning causes nearly 40% of all natural disaster-related deaths every year,” he says, citing NCRB data.
As climate change increases heat and extreme convection, lightning risk is likely to rise further. While India’s early warning systems, such as the Damini app, have helped reduce fatalities, Chowdhury says the study shows that integrating air-pollution information into weather forecasting models could further improve lightning prediction, especially during extreme events.
According to him, this integration is a crucial step towards reducing lightning-related deaths in the country.
Read more: Cloud seeding not a proven solution for air pollution
Banner image: A bolt of lighting strikes over in Jammu. (AP Photo/Channi Anand)
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