Nacreaous clouds over Teirra Del Fuego

NACREOUS CLOUDS OVER TIERRA DEL FUEGO

On July 24th, about an hour after sunset, Gerardo Connon of Rio Grande city in Tierra del Fuego, Argentina, walked outside and witnessed a rare display of nacreous clouds. The colorful apparition was as bright as the street lights in the city below:

 

These clouds, also known as "mother of pearl clouds," form in the stratosphere far above the usual realm of weather. They are seldom seen, but when they are, the reports usually come from high-northern parts of our planet. This apparition over Tierra del Fuego was unusual indeed.

Atmospheric optics expert Les Cowley explains the special conditions required to create such a cloud: "Take an unusually cold lower stratosphere (15-25km high), use some gravity waves generated by high winds and storms in the troposphere to stir in some water vapour, and -- voilà! You get these clouds made of tiny ice crystals shining after sunset with unforgettably bright iridescent colors."

"The very special conditions make nacreous clouds a rare, high-latitude phenomenon. Scandinavia, Iceland and northern Canada are favourite places to see them. Sightings in the southern hemisphere are even more rare because there is so little land far enough south except for Antarctica."