The UV index is defined as a measure of the intensity of the sun’s ultraviolet radiation. In Canada the UV index ranges from 0 to 11+. UV levels are influenced by environmental factors:
- Sun height-the higher the sun in the sky, the higher the UV radiation. The maximum levels occur at noon during the summer months.
- Latitude-levels of UV radiation are higher as you get closer to the equator.
- Cloud cover-UV levels can still be high because of the water molecules and fine particles in the atmosphere.
- Altitude-UV levels are higher when at a high altitudes, such as when down hill skiing. The atmosphere is thinner and less UV is filtered.
- Ozone-some of the UV is absorbed by the ozone.
Reflection-UV can be reflected or scattered from ground surfaces. Snow reflects up to 80%, while sand, cement, grass reflects 15% and sea foam about 25%.