Skiers and snowboarders may find themselves sporting a sunburn after a day on the slopes. Increased sun exposure at higher elevations is partly to blame, according to Steven Fassnacht, a professor of snow hydrology at Colorado State University.
“The atmosphere blocks out some of the ultraviolet components of the radiation that burns you, and so when you go higher, you have less atmosphere, less particles to block that out,” said Fassnacht. He said another important source of ultraviolet (UV) exposure is the radiation that reflects off of the snow.
“We think of the snow as being shiny, and that shininess is something that we call albedo,” Fassnacht said. Albedo is the ratio of how much light is reflected by a surface compared to the total light received.
“The albedo of fresh snow is approaching one, which means that it's almost a mirror. … It can be up to about 95%, which means that 95% of the sun that's coming in will get reflected back,” Fassnacht said. The angled surfaces of snowflakes act as tiny mirrors to reflect sunlight.
“As snow gets older, that fresh snow goes from that classic snowflake that you cut out from a piece of paper as a kid, to being something that's more rounded. And that rounded snow has an albedo of about 70%,” Fassnacht said.
Prime skiing and snowboarding conditions often coincide with higher levels of UV radiation.
“When do we want to ski? We want to ski those bluebird days, and that means that we have had a nice fresh dump of snow, and that snow is really shiny," Fassnacht said. "It's a nice blue sky, meaning the clouds are not blocking any of that incoming sunlight, and we're getting that double dose.”
Instead of avoiding the slopes when the sun is out, Fassnacht recommends wearing protective layers and sunscreen.
“Go and have a fun day out on the ski resorts. But just be cognizant of the fact that sunburn can be dangerous,” Fassnacht said.
