1174 
breakup of the storm clouds as the center or front 
passes. The various types of sky indicated by the com- 
bination of the current Cu, Cm, and Cy have been 
related to the different portions of cyclones, anti- 
cyclones, and frontal systems and to their intensification 
or weakening. Thus the synoptic maps of types of sky 
will, by. themselves, give a fairly complete picture of 
the positions and intensities of the cyclones, anti- 
cyclones, and fronts of a weather map. Moreover, the 
diurnal sequence of cloud forms characterizes the type 
of air mass so well that other features of air mass 
weather can often be forecast. 
An Historical Summary of Cloud Synoptics. Ley, im 
England, was the first (1872) to show Cz motion on a 
synoptic chart [61], and the first (1878) to make a com- 
posite chart of cloud distribution in a typical cyclone 
[60], which included forms and motions and showed the 
open sector clear to the center on the south and south- 
west, with the storm as a whole moving northeastward. 
Hildebrandsson, in Sweden, was the first (1883) to make 
a systematic study of the distribution of meteorological 
elements, including the kinds of clouds and their mo- 
tions, about barometric minima and maxima [50]. In 
the United States, Davis [32], in 1894, published a gen- 
eralized, dynamic cloud cross section of a tropical 
cyclone and a generalized map of Cz and other clouds 
and rain, winds and isobars of a well-developed low; 
in 1896°Clayton [23] published a monumental study of 
the distribution of cloud forms and their motions in 
cyclones and anticyclones at Blue Hill as compared with 
Europe, including tables, cross sections, and maps of 
averages and frequencies; Sweetland [98] followed in 
1897 with the cyclonic and anticyclonic distribution of 
special cloud forms, and in 1900 Bigelow [7] published 
a detailed 747-page study of the cloud observations at 
stations throughout the country. The works of Ley, 
Hildebrandsson, Clayton, and Bigelow were outstand- 
ing contributions to our knowledge of the characteristics 
and circulations of cyclones and anticyclones. These 
(except Bigelow’s) and other researches have been bril- 
liantly analyzed and collated by Hildebrandsson and 
Teisserenc de Bort [51]. Brooks [11] interpreted, with 
a cross-section diagram, the cloud details observed at 
Washington during the passage of a strong cyclone in 
1919. During World War I, the French and Norwegians 
were handicapped by a lack of weather data from the 
west, and had to base their weather forecasts largely 
on synoptic interpretations of the cloud systems they 
observed coming in from the Atlantic. Indeed, this 
led to the development of air-mass and frontal analysis 
in Norway. 
Bjerknes, in 1919, first related the cloud pattern to 
frontal systems, with diagrammatic maps and cross sec- 
tions [8] and, in 1922 with Solberg, added occlusions 
{9]. Though Guilbert [48] had laid the groundwork in 
1922, Schereschewsky and Wehrlé [85] developed the 
mapping of cloud- systems in France in 1923. In de- 
veloping the dynamics of air masses and fronts, 
Bergeron in 1928 [4] found clouds helpful. He and 
Wehrlé, as the most active members of the Inter- 
national Commission for the Study of Clouds. from 
CLOUDS, FOG, AND AIRCRAFT ICING 
1926 to 1932 worked cloud synoptics into the relatively 
simple pattern presented verbally and diagrammatically 
in the International Atlas of Clouds and States of the 
Sky [53]. This pattern was amplified by Dedebant and 
Viaut in 1936 [83] and more clearly depicted by means 
of cloud cross sections along five lines through an oc- 
cluded cyclone, and a map of two cloud systems in 
western and central Europe on February 21, 1935. 
Viaut [100] has recently improved the idealized pattern 
and combined the five cross sections into four. Other 
sections of single storms have been made, giving the 
details of growing winter cyclones. Photographs from 
an airplane were taken by Conover [25] to illustrate a 
cold front, by Douglas [42] to show a cold front and 
squall line, and diagrams were drawn by Simon [90] to 
show fronts in Hgypt. 
Alpert [1] and Berkofsky [6] report the use of low- 
and middle-cloud sky-cover charts over the eastern- 
most tropical portion of the Pacific Ocean during World 
War IJ. These were based on information obtained 
from patrol flights. In some cases, isolines were drawn 
for every 0.2 of cloud cover. Such charts proved to be 
“exceedingly helpful m locating the intertropical con- 
vergence zone.” Though not strictly synoptic, this was 
only a slight drawback, for the zones were quasi- 
stationary. 
In 1948, Deppermann [84], after a study of C2 stripes 
in the Philippine Islands, wrote, ‘Since upper-air cur- 
rents are themselves subject to considerable changes of 
path as they proceed, it is evident that an intelligent 
use of striped Cz to indicate the seat of frontal action 
or a typhoon center demands a good network of upper- 
air wind and velocity data.” 
Cloud Cross Sections. In 1926 and 1928, respectively, 
Stiive [92] and Kopp [59] used Lindenberg data (non- 
instrumental and range-finder observations of clouds 
in detail, and records from kite, balloon, and airplane 
meteorographs) as bases for very detailed representa- 
tions of temperature inversions, of circulation, cloud, 
and precipitation cross sections of a warm front, of 
primary and secondary cold fronts (Stiive), and all the 
way from anticyclone center to anticyclone center across 
an occluded front (Kopp). Stiive [94] improved the 
details of his warm-front section in 1937 and added a 
cross section through a cold air tongue. In 1943 Schinze 
and Siegel [87, Figs. 61, 62, 64, 65, 75, 76] published 
detailed cross sections of warm, cold, and occluded 
fronts, in which the composition of the clouds (ice, 
supercooled water, ice and water mixed) and type of. 
precipitation (five types) are shown. 
Schneider-Carius [88] has just published a critique of 
cloud systems, stating that “with the vast experience 
gained from meteorological flight observations Sttive’s 
cloud system, as a sequel to that of Bjerknes, is con- 
sidered as antiquated, [while] retaining their importance 
are the cloud systems of Schinze-Siegel, Schwerdtfeger, 
and Wehrlé.” He finds a “ground layer” the types of 
which have definite relations to the various states of the 
low-cloud types of sky of the Atlas of Clouds and apply 
in the tropics as well as in middle latitudes. 
Detailed studies of clouds in a particular cyclone are 
