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 dryer weekends. The findings are from a study led by Thomas Bell, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Bell says the trend could be attributed to atmospheric pollution from humans, which also peaks midweek.
He and his colleagues reported their results on 31 January in the Journal of Geophysical Research - Atmospheres, a publication of the American Geophysical Union.
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 his colleagues looked at the big picture from Earth's orbit. The team collected data from instruments on the TRMM satellite, which they use to estimate daily summertime rainfall averages from 1998 to 2005, across the entire Southeast.
The team finds that, on average, it rains more between Tuesday and Thursday than from Saturday through Monday. Newly analyzed satellite data show that summer 2007 echoes the midweek trend with peak rainfall occurring late on Thursdays. However, midweek increases in rainfall are more significant in the afternoon, when the conditions for summertime storms are in place. Based on satellite data, afternoon rainfall peaks on Tuesday, with 1.8 times more rainfall than on Saturday, which experiences the least amount of afternoon rain.
The team uses ground-based data from rain 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 analyzes 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, show that pollution tends 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,"
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. When conditions are ripe for 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 says. He and his colleagues find that the radar on the TRMM satellite shows 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 that it will always rain on weekday afternoons during summertime in the Southeast. Rather, "it's a tendency," says Bell. 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 says, "probably under-predict rain during the week and over-predict rain on weekends."
Notes for Journalists
Journalists and public information officers of educational and scientific institutions (only) who have registered with AGU for direct electronic access and received a username and password, can download a PDF copy of this paper by clicking on this link http://dx.doi.org/10.1029/2007JD008623 . If you need instructions for downloading, please see http://www.agu.org/jinstructions.shtml .
Or, you may order an emailed copy of the paper by sending a message to Peter Weiss at firstname.lastname@example.org. Please provide your name, the name of your publication, and your phone number. Neither the paper nor this press release are under embargo.
"Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms "
Thomas L. Bell: Laboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA;
Daniel Rosenfeld: Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel;
Kyu-Myong Kim and Myong-In Lee: Laboratory for Atmospheres, NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA, and Goddard Earth Sciences and Technology Center, Univ. Maryland Baltimore County, Baltimore, Maryland, USA;
Jung-Moon Yoo: Department of Science Education, Ewha Womans University, Seoul, South Korea;
Maura Hahnenberger: Meteorology Department, University of Utah, Salt Lake City, Utah, USA.
Bell, T. L., D. Rosenfeld, K.-M. Kim, J.-M. Yoo, M.-I. Lee, and M. Hahnenberger (2008), Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms, J. Geophys. Res., 113, D02209, doi:10.1029/2007JD008623.
Contact information for coauthors:
Thomas L. Bell, senior meteorologist: office +1 (301) 614-6197, Thomas.L.Bell@nasa.gov
Peter Weiss | American Geophysical Union
Sea ice extent sinks to record lows at both poles
23.03.2017 | NASA/Goddard Space Flight Center
Less radiation in inner Van Allen belt than previously believed
21.03.2017 | DOE/Los Alamos National Laboratory
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.
Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
23.03.2017 | Life Sciences
23.03.2017 | Power and Electrical Engineering
23.03.2017 | Earth Sciences