What factors affect the amount of UV radiation that reaches the Earth?
Although the ozone layer is the one constant defence against UV penetration, several other factors can have an effect: • Ozone: Lower ozone values in the atmosphere lead to higher UV levels, and conversely, higher ozone values lead to lower UV levels. Ozone levels are affected by weather patterns in the upper atmosphere. Areas of converging air in the upper atmosphere generally have slightly higher ozone values resulting in slightly lower UV levels, and areas of diverging air in the upper atmosphere have slightly lower ozone values resulting in slightly higher UV levels. • Latitude: Since the sun’s UV energy impacts the Earth’s surface at the most direct angle over the equator it is the most intense at this latitude. Also ozone is transported by large scale circulations in the upper atmosphere, from equatorial regions towards the polar regions, resulting in generally higher values of ozone, and therefore lower levels of UV. • Time of day: On any day the greatest amount of UV reaches th
