© Art Rangno
Baby Jesus Trail, Pima County, Arizona, United States of America.
Latitude: 32° 28' 31'' N
Longitude: 110° 51' 54'' W
18 May 2011 1042 (Local Time)
Camera direction: towards SW
Image P/S code: P.7.9
Image I.D.: 5704
CL = 8, CM = /, CH = /
This mostly dark grey layer of cloud is typical of the genus Stratocumulus. It has a relatively high base and is arranged as an extended sheet or layer with the elements more or less flattened, identifying the species as stratiformis. As most of the layer is sufficiently opaque to mask the Sun, it is of the variety opacus. However, towards the lower left of the image at 3 and 4 are two very small gaps where blue sky is visible; therefore, we may identify the variety perlucidus in that area. Near the distant horizon, small Cumulus can be seen
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The Tucson, Arizona, USA (WMO 72274) sounding, taken some hours before the image, shows moisture around 3 000 m above mean sea level. Calculation reveals that the Stratocumulus layer had an estimated base of about 2 000 m above ground level at the location of the image. This puts the cloud base at the upper limit for Stratocumulus.
The dense Stratocumulus layer is sufficiently opaque throughout to be identified as Stratocumulus opacus. A somewhat wrinkled structure (1, 2) of its under-surface becomes vaguely visible as a result of the grazing twilight illumination. Cumulus clouds (3, 4) with distinct horizontal bases and large vertical bulges enter the upper layer. There are also some Cumulus fractus clouds.
The station was in a north-easterly flow of maritime polar air on the southern edge of a high centred over Spitsbergen.
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