- New Regulations Lead to a 50% Drop in Lightning Activity.
- Lower Sulfur Emissions Trigger Major Lightning Decline.
- Cleaner Fuels Reduce Thunderstorm Intensity Over Shipping Routes.
If you look at a lightning map close to the Port of Singapore, you’ll see a clear streak of dense lightning activity over the busiest shipping route in the world. This isn’t an accident—lightning activity is affected by ship emissions and the minute particles they emit, reports The Conversation.
How Ship Emissions Affect Lightning
Analyses of global lightning detection data indicated a strong association between ship exhaust plumes and enhanced lightning rate. Ship emissions increased steadily, as international commerce grew over many decades, promoting more lightning production over busy shipping routes. This changed in 2020 with the implementation of new global sulfur emission controls lowering ship sulfur releases by 77%, providing a natural experiment indicating how sensitive thunderstorms are to aerosol particles produced by people.
The Function of Aerosol Particles in Cloud Formation
Aerosol particles, or particulate matter, naturally occur in the atmosphere and may come from wind, forests, and human activities like transportation and manufacturing. These particles act as nuclei for water vapour to condense on and form cloud droplets.
In shallow clouds, additional aerosol particles create additional cloud droplets, which make clouds whiter as they reflect more sunlight. In storm clouds, the droplets freeze into ice crystals, triggering complicated thermodynamic processes that affect the intensity of storms. Since storm development is very chaotic, separating the influence of aerosol particles has proven difficult. But with the high traffic of ships off Singapore, researchers have a rare chance to observe their influence.
Ship Emissions and Their Association with Lightning
Ships combust fuel in gigantic engines, releasing great quantities of soot and sulfur particles. The Port of Singapore, which processes 20% of the world’s bunkering oil, is among the busiest ship lanes in the world. To cut health hazards, the International Maritime Organization imposed sulfur emission rules in 2020, causing the usage of high-sulfur fuels to plunge drastically.
Why Do Ship Emissions Affect Lightning?
Lightning occurs when ice crystals in storm clouds collide. As lighter crystals ascend and heavier ice crystals descend, the cloud is electrically charged. When the charge reaches a breaking point, a lightning bolt is emitted, travelling at temperatures five times hotter than the surface of the Sun.
Ship emission aerosol particles probably enhance ice crystal number or collision frequency, amplifying cloud electrification.
Dramatic Drop in Lightning After 2020 Regulations
A recent study found that lightning activity over the shipping lane fell by 50% after sulfur regulations were enforced. No other environmental factors, such as El Niño or changes in storm frequency, could explain this sudden decline.
The decrease in sulfur emissions left fewer condensation nuclei for water droplets, resulting in fewer collisions of ice crystals and reduced cloud electrification. Consequently, fewer thunderstorms were strong enough to generate lightning. This inadvertent experiment illustrates the extent to which human activity, even activity at ground level, can have a profound effect on atmospheric processes on a broad scale.
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Source: The Conversation
