Pollution leads to wetter week days

Summer storms tend to be stronger and shed more rain during the working week than at the weekend due to increased levels of pollution from rush hour traffic and industry.

According to scientists from NASA, rainy summer days in southeastern states are more common midweek, when atmospheric pollution from human activity also peaks.

Analysis of satellite data shows that midweek storms tend to span a larger area and drop more rain than their weekend equivalents.

As splitting days into weeks is simply a human convention, there is no natural explanation for this phenomenon and our habits as a species are, according to NASA, the most likely cause of the discrepancy.

“It’s eerie to think that we’re affecting the weather,” said Thomas Bell, an atmospheric scientist at the Goddard Space Flight Centre and lead author of the study.

“It appears that we’re making storms more violent.”

Rainfall measurements collected from ground-based gauges can vary from one gauge site to the next because of fickle weather patterns so, to identify any kind of significant weekly rainfall trend, the research team looked at data from NASA’s Tropical Rainfall Measuring Mission satellite.

This was used to estimate daily summertime rainfall averages from 1998 to 2005 across the entire Southeast USA.

To find out if pollution from humans could be responsible for the midweek boost in rainfall, the team analyzed the concentration of particulate matter, using records from the Environmental Protection Agency.

This showed that pollution tended to peak midweek, mirroring the trend observed in the rainfall data.

“If two things happen at the same time, it doesn’t mean one caused the other,” said Dr Bell.

“But it’s well known that particulate matter has the potential to affect how clouds behave, and this kind of evidence makes the argument stronger for a link between pollution and heavier rainfall.”

Sam Bond

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