Thiên Nhiên : MÂY, ÁNH SÁNG (CẦU VỒNG), TIẾT ĐỘ,  SỨC GIÓ etc..  dễ tạo ra các tác fẫm tuyệt tác nầy.. Rarely Seen Cloud Formations There seems to be no end to strange cloud formations! From Punch hole clouds to cloud vortices, enjoy these rarely seen cloud formations!     Punch Hole Clouds may appear as a circular or oval holes in a layer of supercooled clouds; sometimes they assume a form of a perfect circle and persist for quite a long time, drifting together with the cloud layer. One explanation seems to blame the air traffic (the jet contrail intersections) combined with a thermal inversion (a circular motion of a rising warm air). Here is one, observed over the Gunnison Valley in Colorado: (image credit: Cuerling) Another strange hole in the cloud, reported from Mobile, Alabama USA, Dec. 2003 (and covered by BBC News): (images credit: Joel Knain and Weatherlings) Photo taken in Melbourne, Australia in 2003: (images via) It seems both rising and sinking air currents can create the same effect. Sometimes a very stable, uniform layer of high-altitude clouds can get "punched though" by a pocket of cold air, which sinks toward the ground - creating the circular hole formation. (image credit: Neil Johnson(The Tampa Tribune) and Gwen Swinburne) These "cloud holes" can look like the footprints of some celestial being (UFO enthusiasts rejoice!) or can be amazingly round, like this pair observed in Gallatin, Tennessee by Wayne Carter: (image credit: Wayne Carter) NASA takes satellite images of this phenomenon NASA Terra satellite equipped with the Moderate Resolution Imaging Spectroradiometer (MODIS) has captured these images over Acadiana area in southern Louisiana - a splattering of round holes actually stretched over several states: Oklahoma, Arkansas, Louisiana, and Texas. Some were elongated, some appeared to have smaller clouds inside them.   Cloud Vortices: another "holey" sky phenomena Theodore von Karman's "Cloud Vortices" are something else, again: they form when the wind encounters a barrier - such as the Aleutian islands, in this case - and the flowing eddies of cloud create a weird pattern. The image you see below was photographed from the International Space Station, and the animation shows the double row of vortices, which rotate opposite from each other. (image credit: NASA) More Incredible and Fascinating Clouds ...that make our sky worthy to look at from time to time (those who only look at the computer monitor, take note). Here is an extremely strong thunderstorm cloud that brewed over northwest Calgary: (images credit: D'Arcy Norman) Another supercell cloud in Alberta skies, this time over Edmonton: (image credit: Greg) 'shrooms: (image credit: Cloud Appreciation Society) Another cloud "wave", similar to the one over South Dakota Badlands (see here): (image credit: Barry Slade) Roll clouds... get into a small plane and start "surfing" them! - (image credit: Russell White) (image credit: Dan Bush) A Cloud Angel - (sent in by Dave) Two light-sabers get crossed in the sky: (image credit: Olga Olgert) A fire-breathing rabbit-dragon, and a fantastic cloud edge: (original unknown) A "genie", coming out of a bottle: (image credit: Raoul Pop) Spectacular lenticulars in the morning light... and a whole "pancake" stack of them, over at Mount Rainier in Washington: (image credit: Arco Images, Alamy, National Geographic) Stormy: (image via) An interesting rainbow effect: (original unknown) Nacreous clouds - good page about them, with lots of info: (image credit: Atmospheric Optics) Prepare to get squashed, Earthlings! - (image credit: Sam LeBarron)