A new scientist study shows that pollution is a cause for thunderclouds to form bigger and more deeper than they would naturally, which shows how pollution can affect severe weather and how to gauge how accurate weather and cloud models currently are.

Jiwen Fan of the Department of Energy's Pacific Northwest National Laboratory lead the study, which revealed exactly how pollution is able to change the way thunderclouds form and behave. Previous theories claimed that pollution caused thunderclouds to last longer due to pollution making the clouds draftier through convection. Fan was able to prove that pollution causes water and ice particles in a cloud to form smaller than usual, but increase the actual size of the cloud. As Fan explains to Phys.org:

"This study reconciles what we see in real life to what computer models show us...Observations consistently show taller and bigger anvil-shaped clouds in storm systems with pollution, but the models don't always show stronger convection. Now we know why."

The possible reason behind this effect may have to do with aerosols. Aerosols form naturally, but polluted skies full of smog have much more of the tiny particles. Clouds form around these aerosols particles, so having more of these in the sky causes water and ice particles to spread out across the many different particles and make the cloud bigger, thus causing bigger, stronger, and longer lasting thunderclouds.

These clouds also play into rising global temperatures as well. High atmosphere thunderclouds are anvil-shaped, and this causes sunlight cool the Earth during the day by absorbing light and shadowing the ground. These clouds then trap heat by the time the sun sets, thus leaving a warmer night for people to enjoy. However, these long lasting pollution powered clouds last much longer, heating the Earth more than was naturally possible and thus causing warmer temperatures overall.

Scientists began reexamining their cloud and weather models after the previous convection model failed to explain how clouds in heavily polluted areas were able to become so big even without strong convection conditions. Therefore, Fan and her colleagues took six months to compare the data collected both from real life cloud data and simulations of polluted cloud formation. Scientists were able to create similar clouds found in the areas of study on the computer simulation even when convection conditions were not very good. Scientists were able to then conclude that pollution is responsible for creating the bigger, denser, and longer lived clouds instead of convection.