ih) 
aI 
(27) 
3~2 
40 
30 
20 
0.10 
OSKAR ESSENWANGER 
A 
O16 025 039 O63 100 258 25! 398 INCHES 
Fira. 5—Resolution of frequency distribution of daily precipitation 
amount into partial components for Asheville, N. C., in September, loga- 
rithmic scale 
the individual groups, with parameters, where 
N is the occurrence in per cent of the total fre- 
quency, Xm the mean amount in inches (for the 
log-normal distribution of the partial collective) 
and go the measure of scatter (in class units, 
which can easily be converted into the logarith- 
mic measure). One of the striking facts is the 
existence of a collective in fall with excessive 
rains (defined by its average daily amount of 
1.3 inches). This should be worth a closer look. 
Therefore, the distribution of daily amounts in 
September has been selected here to illustrate 
the result of the analysis (Fig. 5). We recognize 
Tasie 3—Number of storms n of various types that 
cause precipitation of highest amounts in 
Asheville record, 1907-1956 
Septem- 
bee October 
Item August Total 
| 
=>1.0 inch 41 36 38 115 
Thereof in Group I* 4 6 3 13 
(heavy) 
Caused by hurri-| 15 | 17 | 10 42 
canes 
Cyclones 20 | 16 26 62 
Others 6 3 2 11 
The second line is included in the count of 
the first line and serves merely to compare with 
the last line. More details in text. 
four groups of which the last group to the right 
is the subject of further interest. We find that 
the collectives overlap, but that there is also a 
part where mainly one collective prevails. We 
may now take those ranges for the limits im our 
study of the physical basis of the rainfall process 
for the excessive group. The investigation com- 
bines these groups in the months of August 
through October. Precipitation 21.0 inch for 
all three months was determined as the limit 
where the excessive collective appears almost 
uninfluenced. From Table 3 it is seen that from 
the total of 115 cases with amount = 1.0 inches, 
13 belong to the adjoiming group (heavy daily 
rainfall). The 115 cases were examined using 
synoptic weather maps and the reason for the 
precipitation determined. One-third of the total 
sum and between 40 and 50% in August and 
September is caused by hurricanes which is not 
a surprising result. Fall is the main season for 
these phenomena and Asheville lies in the region 
of their influence. Most of the remaining parts 
were typical bad-weather conditions, where ex- 
tratropical cyclones moved through North Caro- 
lina. Eleven cases had to be listed under mis- 
cellaneous such as other frontal or air-mass rains. 
From the theoretical analysis we expected that 
13 values are part of the adjoining collective 
with another basis of rainfall. Therefore, the 11 
