Air pollution‬‬ particles fuel large storms, may have huge impact on storms :Report

Scientists have previously proven that aerosols, particles suspended in the atmosphere, can influence weather and climate. With their latest study — published this week in the journal Science — researchers with the Department of Energy’s Pacific Northwest National Laboratory showed the smallest particles can encourage the formation and increase the intensity of storms.
“We showed that the presence of these particles is one reason why some storms become so strong and produce so much rain,” PNNL researcher Jiwen Fan, lead author of the new study, said in a news release. “In a warm and humid area where atmospheric conditions are otherwise very clean, the intrusion of very small particles can make quite an impact.”
In 2014 and 2015, scientists measured a range of climate-related variables, using ground-based and airborne instruments, in the Amazon. The research focused on a large swath of rain forest, untouched except for the incursion of Manaus. With a population of 2 million, Manaus is the largest city in the Amazon.
The region offers scientists a unique opportunity to identify and isolate man-made impacts on climate and weather patterns.
Researchers used the data to explore possible links between thunderstorms and ultra fine particles, particles measuring less than 50 nanometers wide, a thousandth the width of a human hair.
When strong updrafts carry larger particles into the atmosphere, they can help seed high-altitude clouds that a play an important role in thunderstorm formation. But the newest research shows ultra fine particles can also trigger the formation of thunderstorms.
When large particles are in short supply at high altitudes, the tiny particles can combine with heat and humidity to generate especially large storm clouds.
The absence of large particles allows for an excess of water vapor. The tiny particles offer condensation opportunities and encourage cloud formation. As the water condenses into millions of tiny droplets, heat is released, which drives powerful updrafts, further fueling cloud formation. Scientists have dubbed this process “invigorated convection.”
“We’ve shown that under clean and humid conditions, like those that exist over the ocean and some land in the tropics, tiny aerosols have a big impact on weather and climate and can intensify storms a great deal,” said Fan. “More broadly, the results suggest that from pre-industrial to the present day, human activity possibly may have changed storms in these regions in powerful ways.”



 New research suggests scientists have underestimated the importance of particulate matter as a driver of storm size and intensity.
Tiny airborne particles can have a stronger influence on powerful storms than scientists previously predicted, a study has found.
The findings, published in the journal Science, describe the effects of aerosols, which can come from urban and industrial air pollution, wildfires and other sources.
While scientists have known that aerosols may play an important role in shaping weather and climate, the new study shows that the smallest of particles have an outsized effect.
Particles smaller than one-thousandth the width of a human hair can intensify storms, increase the size of clouds and cause more rain to fall.
"This result adds to our knowledge of the interactions between aerosols, clouds and precipitation. In areas where aerosols are otherwise limited, such as remote regions of the Amazon rainforest, ultrafine aerosol particles can have a surprisingly strong effect," said Zhanqing Li, from the University of Maryland in the US.
"This finding will help us better understand the physical mechanisms of cloud development and severe storm formation, which can help us develop better storm prediction methods," Li said.
The researchers studied the storm-creating capacity of ultrafine particles that measure less than 50 nanometers across. For reference, a typical human red blood cell is about 8,000 nanometers wide.
They showed how smaller particles can invigorate clouds in a much more powerful way than their larger counterparts when specific conditions are present.
In a warm and humid environment with no large particles to attract airborne moisture, water vapour can build up to extreme levels, causing relative humidity to spike well beyond 100 per cent, the researchers said.
While ultrafine particles are small in size, they can reach large numbers. These particles form many small droplets that quickly and efficiently draw excess water vapour from the atmosphere.
This enhanced condensation releases more heat, which makes the updrafts much more powerful, they said.
As more warm air is pulled into the clouds, more droplets are launched aloft, producing a runaway effect that results in stronger storms.
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