Solar Constant in UV

The total output of the Sun is very constant. It only varies by about 0.1%. It's even called the "Solar Constant", and rightfully so.

But, this is only a total energy difference, not what happens across the spectrum.

Would you believe that in the UV (Ultra Violet) the variation is a lot more than 0.1%? At 121.5 nm (UVC) the variation is over 74%! Data available here. [I used 20 years of daily data.]

But the energy level is tiny at that wavelength, fortunately. The question, nevertheless, is whether or not that large swing in strength somehow acts on sensitive molecules that have a larger effect on the climate? Don't ask me, but it helps to know not to get stuck on the 0.1% "constant".
 
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Very interesting. The effect is probably mitigated somewhat by the fact that such short wavelengths are absorbed very far up in the atmosphere.
Yes. 95% of the UV that does reach the surface is the less brutal UVA. No UVC, fortunately, reaches the surface.

Ozone and O2 seem to be affected by all UV.
 

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