Kleinste 
Niederschlage 
Daver 
der 
Stufenwerte 
0.00010 
0.00017 
0.00023 
000046 
000077 
0.00026 
0.0021 
00035 
0.0058 
0.0096 
nach 
0.016 
JOHANNES GRUNOW 
Niederschlagsdauer / Intensitat 
Tropfenregistrierungen 
Hohenpeissenberg 
1954 -58 
der Falle 
hy Ro 
SN 6) 
0.026 
0.043 
0119 
0197 
0.325 
0.54 
0.89 
Stufenwerte der Intensitat (mm/min) 
Fig. 8—Relationship between duration (ordinate) andintensity (abscissa) of precipitation, demon- 
strated by isolines of equal frequency; minute amounts, derived from raindrop records 
Drop size—The drop sizes of minute precipita- 
tion (Fig. 4) lkewise demonstrate some part 
collectives in the curve of frequency-distribution : 
diameters below 0.5 mm, originating from drizzle; 
a more marked maximum between 0.6 and 0.9 
mm originating from lability showers and a wide 
range from 1.0 to 2.0 mm diameter as effects of 
heavy showers near the station. The effect of 
wind shear, however, which spreads the various 
drops in the spectrum not only in the direction 
of motion of the source but also at right angles 
to it [Blanchard, 1957], will bring more drops 
of smaller size-ranges in this case. The dominat- 
ing range of 0.6-0.9 mm, evident in the summer 
months, therefore seems to shift to smaller ranges 
than is the case for precipitation of higher 
amounts. 
Intensity—The ranges of intensity shift in the 
same manner from higher values in case of the 
total collective (Fig. 5) to smaller values in case 
of minute precipitation (Fig. 6). The differences 
between the ranges of diminutive intensity and 
of higher ones are more conspicuous than be- 
tween other factors of the structure. The minute 
precipitation amounts in the summer months, 
however, demonstrate a secondary maximum in 
the range of 0.0010 to 0.0030 mm/min, originating 
from less abundant shower precipitation. 
The dependence of intensity on duration is 
shown on Figures 7 and 8 which illustrate clearly 
the ranges covered by the cases of minute pre- 
cipitation. They shift to smaller values of both, 
duration and intensity, the angle of inclination of 
the mean line of this relation decreases from 42° 
to 35°. These ranges seem to be of interest in re- 
spect to artificial stimulation of rain. Therefore 
further studies of selected cases ought to clear 
the generating conditions of this minute pre- 
cipitation. 
Conclusions—At the beginning of the paper 
attention was called to the laborious work in 
evaluating the raindrop recordings. To accom- 
plish that, the Observatory Hohenpeissenberg 
has designed two instruments for recording the 
structure of rain. The one records the duration of 
precipitation of any amount im minutes based on 
the dual principle: precipitation or no precipi- 
tation; the other records the intensity based on 
