What fundamentally causes a cloud's deep gray or near-black appearance?

Answer

How much light it scatters, absorbs, and reflects back toward the ground

The dark color of a cloud is an optical phenomenon determined by the physics of light interaction. It depends on how much sunlight the cloud layer scatters, absorbs, and reflects back upward away from an observer.

What fundamentally causes a cloud's deep gray or near-black appearance?

#Videos

Why Storm Clouds Are Dark - YouTube

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