The intensity of ultraviolet (UV) radiation varies significantly with both altitude and latitude due to atmospheric and geometric factors:
Variation with Altitude:
- UV intensity increases with altitude.
- For every 1,000 meters gained in elevation, UV radiation increases by about 10% to 12%.
- This happens because:
- Thinner atmosphere at higher altitudes filters less UV.
- There’s less scattering and absorption by air molecules, ozone, and water vapor.
- Mountain regions and high-altitude cities (e.g., La Paz, Bolivia) experience significantly higher UV exposure than lowland areas.
Variation with Latitude:
- UV intensity decreases as you move away from the equator.
- Highest UV levels are near the equator where the sun’s rays strike the Earth most directly.
- At higher latitudes (closer to the poles), sunlight travels through more atmosphere, causing:
- Greater absorption and scattering of UV.
- Lower sun angles, reducing direct radiation intensity.
- During summer, UV levels can increase even at higher latitudes due to longer days and higher solar angles.
Conclusion:
UV radiation is strongest at high altitudes and near the equator, and lowest at sea level and polar regions, especially during winter.