Konstantin Postovalov, a senior researcher at the Institute of Climate and Environmental Systems, reported that intermittent cloud cover may increase human skin's exposure to ultraviolet radiation compared to clear skies.
Postovalov said, in statements reported by the official publication of the Siberian branch of the Russian Academy of Sciences, "Science in Siberia": "Another important factor is what is known as 'albedo,' which is a measure of the ratio of radiation falling on a surface that is reflected compared to that which is absorbed. In cases of intermittent clouds, especially breakaway clouds with gaps, such as scattered cumulus clouds, this factor can have a significant impact on the level of surface exposure to ultraviolet radiation. As a result, the flux of ultraviolet radiation reaching a certain area may become greater than it is in clear weather."
The scientist explained that the outer edges of clouds act like mirrors, reflecting incoming solar radiation. This exposes humans to direct radiation, diffuse radiation, and reflected radiation, which is essentially a portion of direct solar radiation arriving from a different direction. In this case, the total influx of ultraviolet radiation reaching humans may exceed the level recorded under a clear sky.
The expert explained that tanning results from the darkening of the skin by a natural pigment called melanin . Melanin production is the body's defense mechanism against ultraviolet (UV) radiation, as it helps absorb more than 90% of this radiation. However, the skin remains more sensitive to short-wavelength UV radiation, and excessive doses can lead to burns, which, in the long term, increase the risk of developing skin cancer, including malignant melanoma.
Postovalov pointed out that the presence of scattered clouds, especially cumulus clouds, can give the false impression that unprotected sun exposure is safe. He said this could lead to serious health consequences, emphasizing the need for caution even on cloudy days.
