1166 
conscious people. With the collaboration of the directors 
of national meteorological services, it might be possible 
for such an atlas to be distributed to every weather 
station in place of the several different publications 
now so distributed. 
Another pressing need is for adequate, uniform train- 
ing materials and outlines of study. At present, cloud 
classification is taught not from the International Atlas, 
which is too bulky and expensive for use in the class- 
room or for purchase by individual students, but from 
textbooks that usually accompany brief extracts from 
the international definitions with introductory and ex- 
planatory material that may differ substantially from 
the Atlas. Training material and courses should be de- 
signed to meet the individual needs of introductory, 
intermediate, and advanced stages in the training of 
meteorologists and meteorological observers, and ap- 
propriate special training material should be provided 
for the use of student aviators and other students of 
applied meteorology in its many branches. In order to 
spread uniform training as widely as possible, the publi- 
cations should be realistically designed for inexpensive 
production. Film strips and if possible time-lapse mo- 
tion pictures should be prepared as auxiliary teaching 
aids and given the widest possible distribution. 
Genetical Classifications. Although the international 
classification of states of the sky (nephsystems, as dis- 
tinguished from the Cz, Cm, Cx code) has not gained 
widespread use in synoptic meteorology, the need for an 
internationally recognized genetical classification is 
growing, rather than diminishing. The time is near 
when our body of information about the relation of 
cloud forms to the atmospheric processes that form 
them will be adequate for the purpose and a definitive 
genetical classification will be achieved. 
In the steps toward a comprehensive genetical classi- 
fication, it will be necessary to broaden the basis of 
nephanalysis and make the connection between the 
structure of nephsystems and cyclones more specific. 
The notion of an idealized cyclone that moves steadily 
across the country without changing its structure has 
given way to the concept of a cyclone that passes through 
a definite life cycle of wave development and occlusion. 
The development of the nephsystem should be related 
to that of the cyclone and the connection between them 
should be clarified by an analysis of the atmospheric 
processes that are common to both. 
A Umfying Principle. The form and appearance of 
clouds, which is the basis for the international classifi- 
cation, is the product of the genetical processes that 
formed the clouds, and is influenced by their physical 
constitution. This forms a compelling basis for interre- 
lation between the different kinds of classification so 
far discussed. Since the international definitions have 
intentionally avoided mention of genetical processes as 
much as possible and refer only to aspects of physical 
constitution that are visibly apparent, recognition of 
the interrelations have mostly taken the form of refer- 
ences in the genetical and physical classifications to 
corresponding international cloud types. 
There is nevertheless an inviting possibility that the 
different classifications may benefit mutually through 
CLOUDS, FOG, AND AIRCRAFT ICING 
the development of closer correspondences. There are 
already many instances of almost perfect correspond- 
ence between a cloud form as internationally defined 
and the genetical class into which it falls. For example, 
cirrocumulus is associated with only a single subdivision 
of Sttive’s classification, and it is the only form that 
belongs in that subdivision. The establishment of more 
correspondences of this sort in the course of revising 
the international classification and framing an authori- 
tative genetical classification should materially assist 
in the improvement of both classifications. It provides a 
powerful principle for eliminating the omissions and 
ambiguities now troubling us and for broadening the 
field of general agreement in all aspects of cloud classi- 
fication. 
REFERENCES 
1. Atlas international provisoire des nuages. Paris, Office 
National Météorologique, 1929. 
2. Berceron, T., “Uber die dreidimensional verkniipfende 
Wetteranalyse, I.’’ Geofys. Publ., Vol. 5, No. 6 (1928). 
(See pp. 29 ff.) 
3. —— On the Physics of Clouds. Memo, Meteor. Assoc., 
Intern. Union for Geodesy and Geophysics, Paris, 1933. 
4, —— Vortrdge wiber Wolken und praktische Kartenanalyse. 
Translated from the German ms. by 8. P. CHromovy. 
Moscow, Central Hydrometeorological Service, 1934. 
5. Berry, F. A., Jk., Botuay, E.and Brrrs, N.R., ed., Hand- 
book of Meteorology. New York, McGraw, 1945. (See pp. 
893-901) 
6. Brooks, C. F., “International Cloud-Nomenclature and 
Coding.” Trans. Amer. geophys. Un., Part IIL: 494-502 
(1944). 
7. Cuayron, H. H., ‘Diurnal Cloud and Wind Periods at 
Blue Hill Observatory during 1887.’ Amer. meteor. J., 
5: 321-332 (1888). 
8. Diem, M., ‘‘Messungen der Grésse von Wolkenelementen 
Il.” Meteor. Rdsch., 2: 261-273 (1949). 
9. Doueuas, C. K. M., ‘“‘The Physical Processes of Cloud 
Formation.’’ Quart. J. R. meteor. Soc., 60: 333-341 (1934). 
10. HitpEBRANDsson, H., RicernsBacu, A., et TEISSERENC 
DE Bort, L., Atlas international des nuages. Paris, 
Comité Météorologique International, 1896. 
11. Howarp, L., “On the Modifications of Clouds, and on the 
Principles of Their Production, Suspension, and De- 
struction.”’ Phil. Mag., 16: 97-107, 344-357 (1803); 17: 
5-11 (1803). 
12. Howe.u, W. E., Wexunr, R., and Braun, S., ‘‘A Theory 
for the Drop Size Distribution in Clouds,”’ Part One (II) 
in Contributions to the Theory of the Constitution of Clouds, 
pp. 6-18. Mount Washington Observatory Res. Rep., 
Final Report, year ending Oct. 20, 1949. 
13. International Atlas of Clouds and States of the Sky. Paris, 
Office National Météorologique, 1932. 
14. Kkuter, K., Wolken und Gewitter. Leipzig, J. A. Barth, 
1940. (See pp. 97 ff.) 
15. Perrerssen, S., Weather Analysis and Forecasting. New 
York, McGraw, 1940. (See pp. 35-36) 
16. Poy, A., Nouvelle classification des nuages suivie d’in- 
structions pour servir a@ Vobservation des nuages et 
courants atmosphériques. Paris, Dépot des Cartes et 
Plans de la Marine, No. 513, 1873. 
17. ScuprescHewsky, P. L., et Wenrit, P., “‘Les systémes 
nuageux.’’ Mém. off. nat. météor., Paris, No. 1 (1923). 
18. Strive, G., ‘“Thermodynamik der Atmosphire,”’ Handbuch 
der Geophysik, Bd. IX, Lief. 2. Berlin, Gebr. Born- 
trager, 1937. (See pp. 312-314) 
