The Effect of Clouds on Ultraviolet Radiation
An observational program of the effects of clouds on ultraviolet radiation has been conducted in Southern Ontario for the last three years. Generally when clouds are thick and especially when precipitation is occurring, the UV-B is strongly attenuated. When there are light clouds such as cirrus, the UV-B field can actually be enhanced by up to 25 percent. Rapid variations with enhancements have also been observed with light cumulus clouds.
Measurements with spatial variations showing a cloud edge enhancement effect are shown. This cloud edge enhancement effect can be explained by Mie scattering. It is proposed that jet contrails can actually increase the UV-B exposure levels near large airports.