How is the UV index calculated?
A collection of parameters is used to calculate the UV index, including the spectral irradiance of the sun with a wavelength range between 250 and 400 nm. The irradiance of the different wavelengths, from UVB (since UVC does not reach the Earth’s surface) to UVA is weighted based on its potential to cause burns (sunburn or erythema) on the skin. While over 90% of UVB radiation is absorbed by the atmosphere, it is 1,000 times more effective at causing sunburn than UVA radiation. A person’s sensitivity to UV radiation depends on the amount of skin pigmentation. The dose required to have a noticeable effect on the skin (the minimal erythemal dose) for the European population ranges between 200 and 500 joules per square meter.
UV-index forecast by MeteoSwiss
MeteoSwiss calculates the UV index daily for the following day. This is an automatically generated forecast [Internal link: UV index] based on a radiation model that accounts for the environmental factors mentioned above. Cloud cover is also incorporated into the forecast, and the data is sourced from the ICON model of MeteoSwiss. The index is calculated for the maximum radiation intensity (approximately between 11:00 and 15:00 hours).