The World Health Organization (WHO) and the World Meteorological Organization (WMO) collaborate in providing the UV Index. It is usually presented as a number ranging from 0 to 11+, where higher values indicate higher UV intensity. The UV Index scale is divided into several categories:
- Low (0-2): Low risk
- Moderate (3-5): Moderate risk
- High (6-7): High risk
- Very High (8-10): Very high risk
- Extreme (11+): Extreme risk
Calculating the UV Index involves measuring the amount of UV radiation reaching the Earth's surface using instruments called UV spectrophotometers. These instruments measure the intensity of both UV-A (315-400 nm) and UV-B (280-315 nm) radiation. The measurements are then processed using mathematical models that consider factors such as ozone absorption, atmospheric conditions, and the solar zenith angle (angle between the sun and the zenith).
The UV Index is calculated using the following general equation:
UV Index = UV Radiation Intensity (in mW/m²) / 25
The constant 25 is used as a conversion factor to bring the UV Index into the defined range of 0 to 11+.
The UV Index is calculated in real-time and is constantly being updated throughout the day to reflect changes in environmental conditions. It is an essential tool for informing people about the potential health risks associated with sun exposure and allows individuals to make informed decisions about sun safety precautions, such as wearing sunscreen, seeking shade during peak UV hours, and covering exposed skin.
