Cirrus Clouds (Ci)

The series ThinCirr1.jpg to ThinCirr3.jpg shows a geometrically thin Cirrus layer above an Altocumulus perlucidus translucidus. The Cirrus clouds were close to the cruising altitude of approximately 10 km above Southern Sweden. The vertical extension of the layer is most probably less than 100 m. Nevertheless it is not clear if these are "subvisible" cirrus clouds which will be not visible from the ground.

Taking the size of the particles in the cloud and the cloud thickness into account the optical thickness could be estimated. If it is below 0.03, then it will be a "subvisible" cirrus cloud. An extremely thin, wavy Cirrus layer can be recognized above the clouds in the centre level of WaveCirr.jpg. The optical thickness of this Cirrus cloud is already so small, that it will be classified as "subvisible" cirrus.

ThinCirr1.jpg to ThinCirr3.jpg: S. Borrmann, flight from Stockholm to Frankfurt, 22 June 2002 from 1:00 to 3:00 p.m.

WaveCirr.jpg: S. Borrmann, flight from Frankfurt to Lanzarote, 21 September 2002