Cumulonimbus Clouds (Cb)

The images of the upper row display Cumulonimbus clouds (thunderclouds) above the Taunus, Germany. They were taken from the roof of the new science building of the Johannes Gutenberg University at Mainz. The images at the bottom were also taken near Mainz with view direction to Taunus. The explicit time of exposition is given in the file name.
A totally iced anvil is pictured in the images at the bottom. In contrast still cauliflower-like structures (not iced yet) of the anvil region can be noticed at the images of the upper row.

If a Cumulonimbus cloud forms an anvil, this implies that the under-cooled droplets freeze there and ice is formed. Because of the different scattering of light at non-spherical ice-crystals and spherical water droplets the cloud region appears diffuse, stripy and not cauliflower-like anymore (look also to chapter Sun in the clouds). During anvil formation the complete icing of the upper region of the cloud can take place within few minutes. It can be often easily recognized by a closer look.

0207301237-0207301245.jpg: S. Borrmann, Campus of the Johannes Gutenberg University, Mainz, Germany, 30 July 2002, 12:40 p.m.

0406021.jpg and 0406022.jpg: P. Reutter, Mainz, Germany, 2 June 2004