Ok, so I have another question that online searches have not been able to produce. Everything I've seen online references sound waves, or RF signals, or electromagnetic waves. I know that the reason we can view sunsets and sunrises safely is because of atmospheric attenuation - the amount of "material" (water vapor, pollution, topography, foliage, etc), and of course the more oblique, the more substance there is for the light to travel - but I'm trying to find a publication that can tease out how relative humidity (alone) impacts the degree of atmospheric attenuation. Let's say we are comparing a sunset/sunrise in Arizona with 15% RH, compared to a sunset/sunrise with 90% RH in SC. How much of an impact does that added amount of humidity have? To go with extremes, to make it easy, let's just compare an RH of 0% to an RH of 100%. As always, any insight helps.