Air pollution 'makes clouds last longer'

As well as contributing to climate change, air pollution could also be to blame for the more extreme storms that have occurred over the last few years. With the most recent natural disaster striking the Philippines, a new study has revealed that air pollution may be the cause behind larger storm clouds that last for a longer period of time.

Researchers from the Department of Energy's Pacific Northwest National Laboratory found that the previous belief that air pollution makes thunderheads draftier - due to convection - leading to longer lasting and larger storm clouds could be incorrect. The latest study suggests that storms are made worse by air pollution that lengthens the lifespan and reduces the size of ice and cloud particles.

It was found that pollution in the air allows the ice and water particles to fall slower than they would in a clean atmosphere due to their reduction in size. Because they disperse much slower, the storm clouds last much longer, which could result in more extreme weather. 

The longer lasting clouds could also have an effect on climate change, as researchers revealed that the man-made particle cloud cover serves as a form of insulation, meaning that warm air is trapped beneath it. This could have a huge impact on global warming models.

Jiwen Fan, an atmospheric scientist who worked on the study, said: "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 researchers used data from the Department of Energy as a basis for their models, which were uploaded onto a supercomputer in order to study how long-lasting clouds function. It was found that the process of convection did not occur in every instance of air pollution-affected long-lasting clouds. 

As the models were able to analyse cloud data on a microphysical level, the discovery of air pollution making water and ice particles smaller was made. It was also found that the temperature in areas with long-lasting clouds was colder throughout the day but warmer at night.