What influences the intensity of the sun?
The skin is exposed to UV radiation every day. The intensity of the radiation varies and depends on various factors.
UVA and UVB rays
Sunlight is made up of a continuous spectrum of light that can be divided up into different types of radiation according to the wavelength. UVB radiation, for example, only penetrates the upper layers of the skin. Therefore, UVB radiation is mainly responsible for causing sunburn. UVA radiation, on the other hand, has less energy, but very high exposure can also cause sunburn.
The time of day
About 60% of UV radiation reaches the Earth between 10am and 2pm. During this time, the radiation is particularly intense.
The time of year
During the summer months in Europe, solar radiation is considerably higher than in winter. Therefore, adequate sun protection is essential during the hot months.
The altitude also plays a decisive role in the intensity of UV radiation. For example, in the mountains, the UV radiation is more intense than it is in the valleys.
The geographical position
The closer you are to the equator, the stronger the solar radiation. For example, the solar radiation in Spain is higher than in Germany.
Snow and sand
Sand reflects up to 25% of UVA and UVB rays. Clean snow can reflect as much as 80%.
The intensity of the sunlight is also affected by the weather, for example, the density of the clouds. Radiation is reduced by cloud cover, but appropriate sun protection is still recommended.
In the shade, UV radiation can be up to 50% less. However, adequate sun protection is still essential in the shade.
Even at a depth of half a metre under the water, UV radiation is still 40% of that on the surface.
Indoors, the UV radiation is only 10 to 20% of that outside.
The ozone layer
The ozone layer forms a kind of protective filter around the Earth. It ensures that only certain components of solar radiation reach the surface of the Earth. So-called "holes" in the ozone layer are causing a reduction in the concentration of ozone in certain parts of the world. There, the solar intensity is also increasing because the radiation is not being filtered as much before it reaches the Earth.