Cumulonimbus Clouds (Cb)

This series shows what tropical Cumulonimbus clouds look like from an orbit around the earth, from the ground and from the airplane.

Cb1.jpg, Cb3.jpg, NoAnvil.jpg and Overshoot.jpg: Here the different development stages of Cumulonimbus clouds up to their mature form with cirrus shield at the tropopause can be seen. NoAnvil.jpg displays Cumulonimbus clouds with a central tower that possesses so much kinetic energy that the inversion, which generates the anvil, can be penetrated and exceeded. In Overshoot.jpg it is also notable that single Cumulonimbus clouds - here in the region of Sao Paolo - can be combined to immense cloud systems. Several forms of clouds in different altitudes seem to be messed up for an observer on the ground. So he gets the impression of a "chaotic sky" as it is named by the WMO. Organized "sub systems" in the complete system can be recognized only from the great distance of the earth orbit. The images which were taken from the Space Shuttle are described by the NASA as follows:

Original Caption for Cb3.jpg:
"Field of cumulonimbus. The image was taken with a 250 mm lens. This photograph also shows high-peaking cumulus cloud topping out into cirrus at the tropopause. Photographed over the Gulf of Mexico, the artistic lighting is partly supplied by oblique photography into a low sun angle, but the soft focus effect is caused by high levels of aerosol haze in the atmosphere. Deep-based convective clouds over water are almost always seeded by giant salt nuclei."

Original Caption for NoAnvil.jpg:
"These cumulus thunderheads near Sao Paulo, Brazil, were photographed from almost directly overhead by the STS 41-B crew. This perspective conveys something of the energy that drives these cloud columns to punch up into the atmosphere. The foreshortening resulting from the near-vertical viewing angle disguises the fact that the cloud heads so prominently in view are but the tops of massive thunderhead storm clouds can tower up to 60000 feet in the tropics."

Original Caption Overshoot.jpg:
"The STS 41-B crew shot this oblique photograph just moments after slide #5 (= the image NoAnvilYet.jpg) was taken. Some more fully developed thunderheads can be seen in the same Brazilian storm. When the rising cumulus columns meet the tropopause, or base of the stratosphere, at about 50000 feet, they reach a ceiling and can no longer rise buoyantly by convection. The stable temperature of the stratosphere suppresses further adiabatic ascent of moisture that has been driven through the troposphere by 8-11 degree/mile lapse rate. Instead ice clouds spread horizontally into the extended cirrus heads seen in this photograph, forming the "anvil heads" that we identify from the ground."

CbInc1.jpg to CbInc18.jpg: Here a totally iced Cumulonimbus tower was illuminated during sunset. It developed near Morro Branco in the north-east of Brazil (approximately 9 degrees southern latitude) during summer season. The icing is recognizable because of the stripy and washed-out structures in the upper part of the tower. CbInc2.jpg and CbInc18.jpg display the horizontally extending anvil (incus) of the cloud. The patient observer will notice that the transition from the state of Cumulus congestus over the intermediate state of Cumulonimbus calvus to the formation of the anvil with complete icing can occur within 15 minutes. The icing itself proceeds within a few minutes only and is well-recognizable taking a closer look.

CbInc19-23.jpg: At the cruising altitude of 11300 m a major Cb with extended anvil is found below the wing of the MD-11. According to the board instrumentation the images were taken at the latitude of Receife and the longitude of Fortaleza at an outdoor temperature of - 49 deg C. At these temperatures under-cooled cloud droplets cannot exist anymore. Existing droplets convert to ice particles by homogenous or heterogenous freezing. In the neighbourhood of the Cb wide fields of Cumulus congestus as well as Cumulus mediocris are found (at CbInc19.jpg).

CbInc24-26.jpg: During the same flight the aircraft closely passed a Cb. In CbInc25.jpg the iced incus can be realized in a semicircle structure. It is placed right below the winglet (i.e. the upwards folded wing tip) in direction to the cabin window. Further one can conclude from the bending of the wings that strong turbulences occurred during this part of the flight.

CbInc27-32.jpg: A Cumulonimbus cloud was observed from the ground whose upper part was advected ("stretched") in easterly direction due to wind shear. In the background of CbInc27.jpg another Cb tower is located on the right side. This is more clearly shown in CbInc30.jpg. It becomes obvious that its incus was not affected by the distortion due to wind shear. In the foreground of CbInc27.jpg and CbInc30.jpg the icing of the incus can be especially distinctly noticed thanks to the stripy structure of the cloud shield. At the right side of CbInc31.jpg and in the middle of CbInc32.jpg one can subtly recognize the veil "cap" of a pileus.

Cb1.jpg, Cb3.jpg, NoAnvilYet.jpg and OvershootAnvils.jpg copied from: Pat Jones, Shuttle views the Earth: Clouds from Space, 1989.

A collection of cloud pictures taken at different flights of the Space Shuttle can be found here. Copyrights belong to the NASA (October 2002).

CbInc1-18.jpg: S. Borrmann, Morro Branco near Fortaleza, Ceara, Brazil, 23 February 2004, 5:50 p.m. to 6:06 p.m.

Cb4.jpg: S. Borrmann, Morro Branco bei Fortaleza, Ceara, Brasilia, 23 February 2004, 10:08:31 a.m.

CbInc19-26.jpg: S. Borrmann, flight from Sao Paulo to Fortaleza, Brazil, 18 February 2004, 1:47 p.m. to 1:50 p.m.

CbInc27.-32.jpg: S. Borrmann, Morro Branco bei Fortaleza, Brazil, 23 February 2004, 2:55 p.m. to 3:07 p.m.

Camera Parameters

Olympus E-1 SLR with a 14-54 mm objective. Light exposure and ASA sensitivity choice was performed by the program automatic. The images were taken in the sRGB colour range with a resolution of 2560 x 1920 Pixel x 24 colours. Since the whole situation from CbINc1.jpg to CbInc18.jpg was extremely dark and the ambient temperature was higher than 30 deg C, the noise level of the CCD recording elements became visible. (It becomes larger when the CCD chip gets warmer). The noise level could be reduced by a special function of the camera.

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