The colors in this image represent the difference in nighttime brightness of city lights during the holidays. Green areas indicate an increase in brightness, yellow areas were unchanged and red areas had a decrease. Jesse Allen, NASA’s Earth Observatory
The colors in this image represent the difference in nighttime brightness of city lights during the holidays. Green areas indicate an increase in brightness, yellow areas were unchanged and red areas had a decrease.
SAN FRANCISCO—People love the holidays so much you can see it from space.
Data collected by a satellite with a special nighttime sensor found that the glow from our collective light displays brightens many major U.S. cities as much as 50 percent between Thanksgiving and New Year’s Day.
A team led by NASA scientist Miguel Román presented nighttime light data from the Suomi NPP satellite yesterday during a press conference here at the American Geophysical Union meeting.
The polar-orbiting satellite, jointly run by NASA and NOAA, has an instrument that gathers data in 22 different bands of visible and infrared light. It can detect all sorts of light including fires, auroras, moonlight reflecting off of ice and clouds, the nocturnal glow of the atmosphere, highway lights, and even the light from a single boat in the sea.
Román’s team used an algorithm to filter out all the lights except for lights in 70 U.S. cities for the past two years. They found that major cities such as Dallas, Washington D.C. and Phoenix were between 20 and 50 percent brighter during the holiday season. They limited their study to cities that don’t typically see snow, which is so reflective that it throws measurements off.
The maps above show the brightness difference during the holidays relative to the rest of the year. Red areas indicate a decrease in brightness, yellow areas were unchanged, and green areas were brighter. If you look closely, you can see some patterns emerge.
“Where are the green areas? They are in the suburbs and the exurbs and the periphery,” Roman said. “People are leaving work for the holidays and they’re turning on the lights.”
The U.S. isn’t the only place brightening for the holidays. The pattern was also clear in 30 major towns in Puerto Rico, which is known for its nighttime holiday celebrations.
Suomi NPP also picked up a change in the Middle East. Román and Eleanor Stokes, a graduate student at Yale University, saw a distinct nighttime brightening there during Ramadan. Because Muslims fast between dawn and dusk during the holy month, a lot of activity shifts to later in the evening, causing a measurable increase in brightness in cities such as Cairo and Riyadh. Other cities, such as Instanbul, had a much smaller increase, and some regions in places like Syria and Iraq had no change at all, possibly due to unstable electrical grids, conflict, or cultural differences.
Roman and Stokes were even able to pick out distinct differences between neighborhoods in Cairo and compared the relative brightness to socioeconomic data. They found that for much of Ramadan, lighting did not increase in some of the poorest and most devout areas of the city. But, all of Cairo lit up for the celebration marking the end of Ramadan.
“These nighttime lights really are in some ways the EKG of cities,” Stokes said.
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