I've read that UV light cannot "penetrate" the atmosphere as easily during winter. But what does this exactly mean? My hypothesis is that due to rayleigh scattering, since light with smaller wave lengths are more scattered, the UV light doesn't end up reaching the surface of the earth. But, this hypothesis isn't water tight, because blue light is still visible in winter. Yes, UV light has a much smaller wavelength than blue or violet light and therefore could scatter much more in winter, but since the sky is still blue in winter, I am not convinced that just due to the angle of the sun in winter, there is less UV light.
Another thing, even if the UV light is more scattered, wouldn't that just mean, that there is a higher chance the scattering points eventually go back into space i.e. we are still getting UV light but at a less intensity as say in summer?
With this logic, the amount of blue light that we see in the sky would also have a less intensity in the winter, right?