Washington, Feb 2 : Rainfall data collected from a NASA satellite has shown that it rains more in the middle of the week than on weekends in southeastern United States.
According to data obtained from NASA's Tropical Rainfall Measuring Mission satellite, known as TRMM, summertime 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, Maryland, who is the lead author of the study.
For the study, the research 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 also 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.
Researchers found that, on average, it rained more between Tuesday and Thursday than from Saturday through Monday. Newly analyzed satellite data show that the summer of 2007 echoed the midweek trend with peak rainfall occurring late on Thursdays. owever, 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.
According to Bell, this unnatural phenomenon can be attributed to atmospheric pollution from humans, which also peaks midweek.
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 US from 1998 to 2005. he data, obtained from the Environmental Protection Agency, showed that pollution tended to peak midweek, mirroring the trend observed in the rainfall data.
According to Bell, "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."
"It appears that we're making storms more violent," he added.
The trend of heavier rainfall in midweek 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," he said.