CODE SPECIFICATIONS 

 LOWER CLOUDS C^ 



0. No Lower Clouds. 



1. Cumulus of Fine Weather (1).^ 



This is observed under different aspects: 



A. In a state of formation, in general in the morning. 



B. Completely formed in general in the middle of the day, with 

 definite horizontal bases, the air being more or less calm; these are 

 (a) w^ith rounded tops but without "cauhflower" heads, or (6) flat 

 and "deflated." 



C. Completely formed but broken up by the wind; in this case they 

 remain separate and are white in color (2). 



The cumulus clouds of fine weather usually have a marked diurnal 

 period on the continent, growing until the middle of the afternoon, 

 and decreasing later, both as to amount of cloud in the sky and in 

 their vertical development. 



These cumulus clouds are found only at a distance from disturb- 

 ances. Wlien the veil of cirrostratus, which fringes the front of a 

 disturbance, begins to cover the sky, the cumulus of fine weather 

 changes from type Ba to type Bb and finally disappears entirely. 



The fractocumulus of fine weather noted above and coded as 0^=1, 

 must not be confused with the fractocumulus of bad weather which 

 is coded 0^ = 6, or (7^ = 9. The former are ((7^=1) detached white 

 clouds usually in a blue sky, and remain detached; the latter are 

 found in the central part of a disturbance or in its rear; in the first 

 case (Ci = 6) they form ^ under a gray sheet of altostratus or of 

 nimbostratus; in the second case (0^ = 9), in a sky crowded with 

 clouds at all altitudes, they form under the bases of cumulonimbus or 

 very large cumulus clouds or in the spaces between these. In both 

 cases they are dark, receiving little light, and generally become very 

 numerous, while the fractocumulus clouds of fine weather usually 

 show white on a blue sky, and remain detached. 



2. Cumulus, Heavy and Swelling, Without Anvil Top (3, 4). 



There are two types of these: 



A. In calm air and especially on hot days with a thundery tendency 

 they form heavy masses with horizontal bases, and very great vertical 

 development. They are sometimes in the form of towers, sometimes 

 of complex heaps with "cauliflower" formation. They often have 

 caps or hoods (pileus). 



B. In strong winds in the rear of disturbances they also form tower- 

 ing masses, with great vertical development but tossed about and 

 broken up. 



These cumulus clouds, especially those of the second class, are often 

 associated with thick cirrus (C^ = 3) and with extensions of strato- 



* Numbers in parentheses after code classifications refer to cloud pictures which illustrate the codes. 



2 Fractocumulus clouds of bad weather (Cl=6) develop under a sheet of altostratus or nimbostratus and 



should not be confused with fractocumulus which persist from a previous disturbance or exist independently. 



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