278 
classification as to advective or convective types. 
Dr. Bergeron, at the opening of this conference, 
has outlined some possible schemes. 
Another way could be to keep the duration for 
the summation short so that we may be able 
to comprehend the intensity groups. Hourly 
sums may be close to the goal. Literally, it means 
to cut off parallel strips in Figure 6 which dem- 
onstrate the two dimensional analysis. 
Conclusion—The author has tried to discuss 
some of the difficulties we have to face with 
commonly available sources of data for precipi- 
tation, when we are interested in the mterpreta- 
tion leading to the physical basis of the rainfall 
process. Besides the statistical techniques avail- 
able for a linear scale, it could be demonstrated 
that the logarithmic scale may also be employed. 
How to study frequency distributions for in- 
vestigations of the physical basis of the rainfall 
process has been demonstrated on the example 
of daily precipitation amounts in Asheville for 
the time of August through October. For the 
selected collective of excessive daily rainfall, de- 
rived by theoretical analysis, the connection to 
the generating process of rainfall can be ex- 
plained. The result differentiates between rain- 
fall from hurricane appearance on the southeast 
coast of the United States and extratropical cy- 
clones through North Carolina as the possible 
reasons. This shows that collectives selected by 
using daily precipitation amounts may not be 
completely uniform in the physical origin. 
Therefore, the question is justified. Is the pre- 
cipitation amount an adequate parameter for 
the interpretation of the rainfall process? A two- 
dimensional analysis of intensity and duration 
for single rainfall data in Braunlage, Germany, 
points out the limitations we have to expect. If 
they can be accepted, the material in the present 
form is sufficient. For refinement of the analy- 
sis, however, it is necessary to do more research 
on rainfall intensity data which may be aided 
by radar analysis. We may study the classifica- 
tion groups of convective and advective type. 
Using the duration as parameters in the pres- 
ently convenient form of equal time intervals, 
we may find that probably the daily amount is 
the upper limit needed to study the physical 
processes involved. A shorter time interval would 
be preferable. Hourly precipitation values have 
OSKAR ESSENWANGER 
been prepared by the U. 8. Weather Bureau on 
a routine basis for several years at a number of 
stations and might be sufficient. However, much 
more study has to be done on this subject before 
final recommendations can be made. 
REFERENCES 
Barcer, G. L., ano H. C. 8. THom, Evaluation of 
drought hazard, Agronomy J., 41, 519-526, 1949. 
Barcer, G. L., Preliminary report to Technical 
Committee on Relation to Weather on Agricul- 
ture (NC-26), unpublished manuscript, Iowa 
State College, October 11, 1957. 
Cuow, Ven Tr, The log-probability and its engi- 
neering applications, Proc. Amer. Soc. Civ. Eng., 
80, 536, 1954. 
Essenwancer, O., Neue Methode der Zerlegung 
von Haeufigkeitsverteilungen in Gaussche Nor- 
malkurven und ihre Anwendung in der Meteor- 
ologie, Ber. Dtsch. Wetterd. 10, 1954. 
Essenwancer, O., Wahrscheinlichkeitsansteckung 
und Erhaltungsneigung beim Niederschlag, Met. 
Rundsch., 9, 13-25, 1956a. 
Esspnwancer, O., Zur Verwendung eines Logarith- 
mischen Maszstabes bei der Niederschlagsstati- 
stik, Met. Rundsch., 9, 197-206, 1956b. 
Essenwancer, O., Tafeln zur Haeufigkeitszerlegung 
mit Anwendungsbeispielen, Ber. Dtsch. Wetterd., 
39, 1957. 
Esspnwancer, O., Linear and logarithmic scale for 
frequency distribution of precipitation, 1959. 
Geofis. Pura e Applicata, in press. 
Grunow, J., Zur Erfassung und Statistik der klein- 
sten Niederschlaege, Geofis. Pura e Appl., 33, 
251-261, 1956. 
Scunerwer-Carius, K., Der Wirkungszuwachs in 
statistischer Betrachtung, Arch. f. Meteor. 
Geoph. u. Bioklim, 6, 22-35, 1954. 
Scunerper-Carius, K., Zur Frage der statistischen 
Behandlung von Niederschlagsbeobachtungen, 
Zs. Met., 9, pp. 129, 193, 266, 299, 1955. 
Tuom, H. C.S., A note on the gamma distribution, 
Statistical Laboratory, Iowa State College, 1948, 
manuscript (manuscript of the U. 8. Weather 
Bureau, 1958). 
Tuom, H. C.S., A statistical method of evaluating 
augmentation of precipitation by cloud seeding, 
Advisory Committee on Weather Control, vol. 
II, pp. 5-25, 1957a. 
Tuom, H. C. S., An evaluation of series of oro- 
graphic cloud seeding operations, Advisory Com- 
mittee on Weather Control, vol. II, pp. 25-45, 
1957b. 
Wanner, E., Ueber die Frequenz der taeglichen 
Niederschlaege, Verh. Schweiz. Naturf. Gesellsch., 
p. 27-00, 1939. 
Wiscumerer, W. H., ano D. D. Smrru, Rainfall 
energy and its relationship to soil loss, Trans. 
Amer. Geophys. Union, 39, 258-291, 1958. 
