Summer in southern Norway is strikingly beautiful, as seasonal snow and ice melt away and expose the region’s famous glaciers and fjords. But as summer turns to autumn (“høst” in Norwegian), another kind of beauty spreads across the landscape.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired an image (left) on September 20, 2022. Though the calendar said it was the final day of summer, many of the trees, shrubs, and grasses had turned from green to autumnal brown and gold.
For comparison, the second image (right) shows the same area on June 29, 2022. In this early-summer view, acquired by MODIS on NASA’s Aqua satellite, snow was still melting away and vegetation was greening in the summer sunlight.
Trees and shrubs change color when cooler air temperatures and fewer sunlit hours trigger them to slow and stop the production of chlorophyll—the molecule that plants use to synthesize food. As the green pigment fades, various yellow and red pigments become visible.
Colors change early in Norway’s northern latitudes, as sunlight wanes faster and cooler air temperatures arrive sooner. Elevation matters too. Cooler temperatures upland generally cause vegetation to change color on the mountains before descending into the valleys.
In some places, green will linger. Forests of evergreen trees, such as spruce and pine, are common in glacial valleys, especially in eastern Norway. But among these forests there are color-changing deciduous trees mixed in, such as birch, ash, rowan, and aspen.
Clear satellite views of Norway are uncommon, as the region is frequently covered by clouds. And views of autumn color here are especially fleeting. Snow is already beginning to cover more of the Scandinavian Mountains compared to late August, and it will eventually blanket most of the region.
NASA Earth Observatory images by Lauren Dauphin, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview. Story by Kathryn Hansen.