Regular observations around the world of giant halos in the sky surface in the medias and are spectacular enough to ignite UFO rumors.

Today this was the turn of CNN  to speculate over the weird formation of a ”hole-punch cloud” over Taiwan. (Article: http://ireport.cnn.com/docs/DOC-729071)

This type of cloud occurs in cirrus or cirrostratus clouds (I recommend you to visit the “cloud appreciation society”, http://cloudappreciationsociety.org for information and pictures), which are often composed of ice crystals and super-cooled water droplets (water that is below freezing temperature, but still in liquid form). When disturbed (e.g. by a plane) the droplets can freeze instantly or evaporate, the latter of which will form the hole.

Interested readers might read a scientific paper that was recently been published in the magazine Science.  “Formation and spread of aircraft-induced holes in clouds” (Vol. 333, 1 July 2011, A. J. Heymsfield from the National Center for Atmospheric Research in Boulder, USA) inquired how a hole in the sky can get punched by airplanes and into the potential for the phenomenon to increase additional precipitation near major airports.  Apparently, as far back as the 1940s, scientists have been wondering about the causes of these weird clouds. Heymsfield is quoted as saying that “these holes did not exist before planes and that before WW2 there were no documented sightings or reports of these clouds”.

http://www.youtube.com/watch?v=z91AZnGX338