Snow - Snow Blindness

Snow Blindness

Fresh snow reflects 90% or more of ultraviolet radiation, which causes snow blindness, also reducing absorption of sunlight by the ground. Snow blindness (also known as ultraviolet keratitis, photokeratitis or niphablepsia) is a painful eye condition, caused by exposure of unprotected eyes to the ultraviolet (UV) rays in bright sunlight reflected from snow or ice. This condition is a problem in polar regions and at high altitudes, as with every 1,000 feet (300 m) of elevation (above sea level), the intensity of UV rays increases by 4%. Snow's large reflection of light makes night skies much brighter, since reflected light is directed back up into the sky. However, when there is also cloud cover, light is then reflected back to the ground. This greatly amplifies light emitted from city lights, causing the 'bright night' effect. A similar brightening effect occurs when no snow is falling and there is a full moon and a large amount of snow.