NASA’s new algorithm measures changes in light usage of major cities around the world.
City lights in the U.S. increased in brightness by up to 50 percent during the holiday season. Image by NASA's Earth Observatory/Jesse Allen.
For the first time, researchers are able to observe changes in light intensity and light output over time from images taken from space. Using an instrument called the Visible Infrared Imaging Radiometer Suite (VIIRS), NASA's Goddard Space Flight Center analyzed how patterns in nighttime light intensity fluctuated during the holidays in major cities. With an advanced algorithm, the VIIRS is capable of sifting through clouds, pollution and moonlight and isolating artifical city lights.
With data collected over a period of three years from 2012 to 2014, they found that lights shone as much as two times brighter during special holiday seasons. In the U.S. during Christmas and New Year’s, lights shine 20 to 50 percent brighter than the rest of the year. According to NASA Goddard’s research scientist Miguel Román, the lights began increasing in intensity on Black Friday and began waning after New Year’s Day.
In the Middle East, lights shine brighter by more than 50 percent during the fasting month of Ramadan – with some cities exhibiting a 100 percent surge in brightness. Because Muslims fast from dawn to dusk in Ramadan – abstaining from all food and drink during daylight hours—activities they would have usually performed in the day are deferred to the nighttime. This explains the extreme increase in light output. Still, some Middle Eastern cities with weak electrical grids actually experienced a decrease in brightness—among them the Syrian city of Damascus and other Iraqi cities.
Ramadan lights of major Saudi Arabian cities. Image by NASA's Earth Observatory/Jesse Allen.
Cairo and Amman lit up during the Ramadan holiday season. Tel Aviv did not exhibit a large change in light brightness. Image by NASA's Earth Observatory/Jesse Allen