Appearance of clouds

When the sun is sufficiently high above the horizon, clouds in direct sunlight are white or grey. However those which receive light from the blue sky are bluish-grey. Some clouds, which appear brilliant white in reflected light, show marked contrasts in brilliance when illuminated from behind. The colour of the sun may change as it approaches the horizon and clouds in the vicinity may show a corresponding colouration. The under surface of a cloud may redden when the sun is on the horizon. Pictured opposite is stratocumulus.

Haze may make distant clouds appear yellow, orange or red. Dust particles introduce a white tinge to the blue of the sky; thus the sky is of a deeper blue when the air has its origins in polar regions.

Related pages: Cloud classification | C_L guide | C_M guide | C_H guide | Cloud index