Feeds

Air pollution driving midweek rain

Wetter Thursdays, drier Saturdays

Build a business case: developing custom apps

NASA has determined that air pollution provokes wetter weekdays and drier weekends in the southeastern US, with peak rainfall occuring late on Thursdays provoked by increased levels of airborne particles.

That's the conclusion of a study of summertime storms using data collected from the agency's Tropical Rainfall Measuring Mission satellite, aka TRMM.

Scientists at NASA's Goddard Space Flight Center, led by atmospheric scientist Thomas Bell, used the data to "estimate daily summertime rainfall averages from 1998 to 2005 across the entire Southeast", and discovered that it "rained more between Tuesday and Thursday than from Saturday through Monday".

The summer 2007 satellite data backed the initial findings, demonstrating that peak rainfall occured "late on Thursdays". Midweek increases in rainfall were generally, however, "more significant in the afternoon, when the conditions for summertime storms are in place" - peaking on Tuesdays which enjoyed 1.8 times more rainfall than Saturdays.

The team then obtained US-wide particulate matter figures for 1998 to 2005 from the Environmental Protection Agency, which showed that "pollution tended to peak midweek, mirroring the trend observed in the rainfall data".

Bell says: "If two things happen at the same time, it doesn't mean one caused the other. 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."

The effect of pollution on the summertime storms is believed to be that the particulate matter "seeds" storm clouds, although some maintain this pollution-based seeding "thwarts rainfall by dispersing the same amount of water over more seeds, preventing them from growing large enough to fall as rain".

However, NASA explains: "In the Southeast, summertime conditions for large, frequent storms are already in place, a factor that overrides the rain-thwarting dispersion effect. When conditions are poised to form big storms, updrafts carry the smaller, pollution-seeded raindrops high into the atmosphere where they condense and freeze."

Bell elaborated: "It's the freezing process that gives the storm an extra kick, causing it to grow larger and climb higher into the atmosphere."

Bell concludes by describing increased midweek rainfall as "a tendency" rather than an absolute, but reckons the team's findings might be used to improve rainfall forecasts which "probably under-predict rain during the week and over-predict rain on weekends".

The researchers' study is published in the American Geophysical Union's Journal of Geophysical Research. ®

Boost IT visibility and business value

More from The Register

next story
Just TWO climate committee MPs contradict IPCC: The two with SCIENCE degrees
'Greenhouse effect is real, but as for the rest of it ...'
Asteroid's DINO KILLING SPREE just bad luck – boffins
Sauricide WASN'T inevitable, reckon scientists
Brit amateur payload set to complete full circle around PLANET EARTH
Ultralight solar radio tracker in glorious 25,000km almost-space odyssey
Boffins spot weirder quantum capers as neutrons take the high road, spin takes the low
Cheshire cat effect see neutrons and their properties walk different paths
NASA Mars rover FINALLY equals 1973 Soviet benchmark
Yet to surpass ancient Greek one, however
Famous 'Dish' radio telescope to be emptied in budget crisis: CSIRO
Radio astronomy suffering to protect Square Kilometre Array
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Maximize storage efficiency across the enterprise
The HP StoreOnce backup solution offers highly flexible, centrally managed, and highly efficient data protection for any enterprise.