Featured Research

from universities, journals, and other organizations

Air Pollution May Be Causing More Rainy Summer Days In The Southeast US

Date:
February 7, 2008
Source:
NASA/Goddard Space Flight Center
Summary:
Rainfall data from a NASA satellite show that summertime storms in the southeastern United States shed more rainfall midweek than on weekends. Scientists say air pollution from humans is likely driving that trend.

Torrential rainfall from a 2003 storm in the Southeast resulted in massive accumulations of rain (red). Similar data from NASA's TRMM satellite has revealed that more rain falls midweek.
Credit: NASA

Rainfall data from a NASA satellite show that summertime storms in the southeastern United States shed more rainfall midweek than on weekends. Scientists say air pollution from humans is likely driving that trend.

The link between rainfall and the day of the week is evident in data from NASA's Tropical Rainfall Measuring Mission satellite, known as TRMM. Midweek storms tend to be stronger, drop more rain and span a larger area across the Southeast compared to calmer and drier weekends. The findings are from a study led by Thomas Bell, an atmospheric scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. Bell said the trend could be attributed to atmospheric pollution from humans, which also peaks midweek.

"It's eerie to think that we're affecting the weather," said Bell, lead author of the study published online this week in the American Geophysical Union's Journal of Geophysical Research. "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, Bell and colleagues looked at the big picture from Earth's orbit. The team collected data from instruments on the TRMM satellite, which they used to estimate daily summertime rainfall averages from 1998 to 2005 across the entire Southeast.

The team found that, on average, it rained more between Tuesday and Thursday than from Saturday through Monday. Newly analyzed satellite data show that summer 2007 echoed the midweek trend with peak rainfall occurring late on Thursdays. However, midweek increases in rainfall were more significant in the afternoon, when the conditions for summertime storms are in place. Based on satellite data, afternoon rainfall peaked on Tuesdays, with 1.8 times more rainfall than on Saturdays, which experienced the least amount of afternoon rain.

The team used ground-based data from gauges, along with vertical wind speed and cloud height measurements, to help confirm the weekly trend in rainfall observed from space.

To find out if pollution from humans indeed could be responsible for the midweek boost in rainfall, the team analyzed particulate matter, the concentrations of airborne particles associated with pollution, across the U.S. from 1998 to 2005. The data, obtained from the Environmental Protection Agency, 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," Bell said. "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."

Scientists long have questioned the effect of workweek pollution, such as emissions from traffic, businesses and factories, on weekly weather patterns. Researchers know clouds are "seeded" by particulate matter. Water and ice in clouds grab hold around the particles, forming additional water droplets. Some researchers think increased pollution thwarts rainfall by dispersing the same amount of water over more seeds, preventing them from growing large enough to fall as rain. Still, other studies suggest some factors can override this dispersion effect.

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.

"It's the freezing process that gives the storm an extra kick, causing it to grow larger and climb higher into the atmosphere," Bell said. He and his colleagues found that the radar on the TRMM satellite showed that storms climb to high altitudes more often during the middle of the week than on weekends. These invigorated midweek storms, fueled by workweek pollution, could drop measurably more rainfall.

The trend doesn't mean it will always rain on weekday afternoons during summertime in the Southeast. Rather, "it's a tendency," according to Bell. But with the help of satellites, new insights into pollution's effect on weather one day could help improve the accuracy of rainfall forecasts, which Bell said, "probably under-predict rain during the week and over-predict rain on weekends."


Story Source:

The above story is based on materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Goddard Space Flight Center. "Air Pollution May Be Causing More Rainy Summer Days In The Southeast US." ScienceDaily. ScienceDaily, 7 February 2008. <www.sciencedaily.com/releases/2008/02/080201215416.htm>.
NASA/Goddard Space Flight Center. (2008, February 7). Air Pollution May Be Causing More Rainy Summer Days In The Southeast US. ScienceDaily. Retrieved April 25, 2014 from www.sciencedaily.com/releases/2008/02/080201215416.htm
NASA/Goddard Space Flight Center. "Air Pollution May Be Causing More Rainy Summer Days In The Southeast US." ScienceDaily. www.sciencedaily.com/releases/2008/02/080201215416.htm (accessed April 25, 2014).

Share This



More Earth & Climate News

Friday, April 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Fungus Killing Bats, Spreading in US

Deadly Fungus Killing Bats, Spreading in US

AP (Apr. 24, 2014) A disease that has killed more than six million cave-dwelling bats in the United States is on the move and wildlife biologists are worried. White Nose Syndrome, discovered in New York in 2006, has now spread to 25 states. (April 24) Video provided by AP
Powered by NewsLook.com
New Pictures of Ship That Sank in 1888

New Pictures of Ship That Sank in 1888

AP (Apr. 24, 2014) Federal researchers have released new images of the City of Chester, a steamship that sank in San Francisco Bay in 1888. Researchers recently found the shipwreck while mapping shipping routes. (April 24) Video provided by AP
Powered by NewsLook.com
Risk of Asteroid Hitting Earth Higher Than Thought, Study Shows

Risk of Asteroid Hitting Earth Higher Than Thought, Study Shows

Reuters - US Online Video (Apr. 23, 2014) A group of space explorers say the chance of a city-obliterating asteroid striking Earth is higher than scientists previously believed. Deborah Gembara reports. Video provided by Reuters
Powered by NewsLook.com
UN Joint Mission Starts Removing Landmines in Cyprus

UN Joint Mission Starts Removing Landmines in Cyprus

AFP (Apr. 23, 2014) The UN mission in Cyprus (UNFICYP) led a mine clearance demonstration on Wednesday in the UN-controlled buffer zone where demining operations are being conducted near the Cypriot village of Mammari. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins