NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet.
Satellite images of Earth at night — often referred to as “night lights” — have been a gee-whiz curiosity for the public and a tool for fundamental research for nearly 25 years.
They have provided a broad, beautiful picture, showing how humans have shaped the planet and lit up the darkness. Produced every decade or so, such maps have spawned hundreds of pop-culture uses and dozens of economic, social science and environmental research projects.
But what would happen if night lights imagery could be updated yearly, monthly or even daily?
A research team led by Earth scientist Miguel Román of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, plans to find out this year.
Today they are releasing a new global composite map of night lights as observed in 2016, as well as a revised version of the 2012 map.
The NASA group has examined the different ways that light is radiated, scattered and reflected by land, atmospheric and ocean surfaces.
The principal challenge in nighttime satellite imaging is accounting for the phases of the moon, which constantly varies the amount of light shining on Earth, though in predictable ways.
Likewise, seasonal vegetation, clouds, aerosols, snow and ice cover, and even faint atmospheric emissions (such as airglow and auroras) change the way light is observed in different parts of the world. The new maps were produced with data from all months of each year. The team wrote code that picked the clearest night views each month, ultimately combining moonlight-free and moonlight-corrected data.
Armed with more accurate nighttime environmental products, the NASA team is now automating the processing so that users will be able to view nighttime imagery within hours of acquisition. This has the potential to aid short-term weather forecasting and disaster response.
“Thanks to VIIRS, we can now monitor short-term changes caused by disturbances in power delivery, such as conflict, storms, earthquakes and brownouts,” said Román.
“We can monitor cyclical changes driven by reoccurring human activities such as holiday lighting and seasonal migrations. We can also monitor gradual changes driven by urbanization, out-migration, economic changes, and electrification. The fact that we can track all these different aspects at the heart of what defines a city is simply mind-boggling.”
For instance, VIIRS detected power outages in the wake of Hurricane Matthew, a major storm that struck the northeastern Caribbean and the southeastern United States in late September 2016.
NASA’s Disasters Response team provided the data to colleagues at the Federal Emergency Management Agency; in the future, NASA, FEMA and the Department of Energy hope to develop power outage maps and integrate the information into recovery efforts by first responders.
The NASA team envisions many other potential uses by research, meteorological and civic groups. For instance, daily nighttime imagery could be used to help monitor unregulated or unreported fishing. It could also contribute to efforts to track sea ice movements and concentrations.
Researchers in Puerto Rico intend to use the dataset to reduce light pollution and help protect tropical forests and coastal areas that support fragile ecosystems. And a team at the United Nations has already used night lights data to monitor the effects of war on electric power and the movement of displaced populations in war-torn Syria.
News source: NASA. The content is edited for length and style purposes.
Figure legend: This Knowridge.com image is credited to NASA Earth Observatory images by Joshua Stevens.