Condensation trails are a common feature in the sky. But those which Richard Henkes saw on June 13, 2013, in Rheinstetten, are really unusual. A number of parallel contrails do not only cast their shadows onto the screen of high cirrus clouds, but also onto a narrow bank of stratocumulus clouds (1 – 2). Due to the different altitude of the two cloud layers, the angle of vision is different for each of the layers. This is why the shadows do not appear parallel to the contrails. Also their shadows in the atmosphere appear under a different angle as these are cast downwards. So they “stand” in the air, and their angle corresponds to the sun elevation at the moment the photo was taken. The shadows on the low clouds, however, are flat or only a little tilted according to the shape of the clouds. Both shadows, the one in the atmosphere as well as the one on the clouds, are seen laterally, which makes a sharp bend appear. And not all contrails and shadows are parallel because the airplanes which caused the contrails did not all fly parallely.

Authors: Peter Krämer und Claudia Hinz