photo #5535066

This Altocumulus cloud showing iridescent colours was spotted by Modestino Carbone (Member 7,416) over Campo Maggiore di Montevergine, Mercogliano, Italy. Its delicate features consist of particularly small water droplets that are all of similar size and that bend, or diffract, the sunlight, separating its visible wavelengths to form the pastel hues of this optical effect. The distinctive curled features of the Altocumulus are yet to be listed in the official reference work for cloud classification, the International Cloud Atlas. And so the Cloud Appreciation Society has proposed it should be acknowledged as an official type and given the name supercilium, from the Latin word for ‘eyebrow’. The short-lived cloud features are frequently, though not exclusively, formed in the turbulent airflows over high mountain peaks