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Urban Patterns in Snow and Light

Urban Patterns in Snow and Light
Urban Patterns in Snow and Light

When a snowstorm hits a metropolitan area, the blanket of white appears—from the street level—to blanket the concrete, steel, and glass of human presence. But from space, these manmade “heat islands” and the network of roads connecting them are clearly visible.

On January 10, 2018, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired an image (top) showing snowfall across central China. Notice how cities stand out as dark gray spots against the otherwise white terrain.

In early January, multiple waves of deadly snowstorms bathed the Henan and Anhui provinces in white. According to news reports, the snow that fell in Henan Province during the first week in January was the worst since records began in 1951; it was the worst in Anhui Province since 2008. The heavy snow damaged thousands of homes and caused widespread destruction to crops.

The second image shows another indicator of human presence—nighttime lights—in the same area. The image comes from a global composite produced in 2016 with data from the Visible Infrared Imaging Radiometer Suite (VIIRS) on the NASA-NOAA Suomi NPP satellite. VIIRS includes a special “day/night band,” a low-light sensor that measures light emissions and reflections, allowing researchers to distinguish the intensity, types, and sources of night lights. Turn on the image comparison tool to see how the patterns overlap.

NASA Earth Observatory images by Joshua Stevens and Jeff Schmaltz, using MODIS data from LANCE/EOSDIS Rapid Response and Suomi NPP VIIRS data from Miguel Román, NASA GSFC. Story by Kathryn Hansen.

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