Question: Why do dangerous clouds always appear dark?
A) They don’t. Clouds associated with severe weather can be as white as the driven snow, but still contain dangerous turbulence or super-cooled water.
B) Water is anything but dark; in fact it’s clear. When it is suspended in very small airborne droplets, it reflects light and appears white. However, when the droplets coalesce into rain, the drops of water absorb more light and will usually appear somewhat darker, especially from below.
C) It has nothing to do with the scattering or absorption of light on an individual droplet or raindrop level. It is simply a matter of attenuation of visible light with increased depth. Storm clouds are usually dark because they are generally quite deep, as with cumulonimbus clouds.
D) They do when the air is dirtier than usual. When air contains particulate matter in sufficient quantity, the clouds will be dark.
Answer:The answer in choice A is the most correct one because of the important fact that some of the most serene looking clouds (such as the milky white lenticular cloud cap above a mountain top) can contain extreme turbulence, or in the case of supercooled water, even stratiform clouds can contain the potential for dangerous icing conditions. Yes, smaller droplets of water do scatter more white light, and yes, thicker clouds absorb more light and can therefore become darker. And there isn’t too much of a correlation between dirty air and dirty clouds. Clouds can also appear dark when they are in the shadow of other clouds, or when the top of a cloud is casting a shadow on its own base, and dark clouds are not always rain clouds. Rainy or snowy days are often dark because clouds simply block sunlight.