SNOW-CRYSTAL ANALY 
Temperature °C 
1 
-25 to -30°}30 to -55° 
-20 to -25°C 
x 
[S) 
& 
= 
i 
# 
-15 to 
Li kp 
Special forms 
0700 0800 
0900 §=1000 N0O 1200 1300 
1400 1500 1600 1700 1800 1900 2000 2100 GMT 
Fria. 1—General survey of observed snow crystals according to Weickmann, showing distribution on 
March 21, 1958 (Operation 27), Hohenpeissenberg, Germany 
physical classification, which also includes their 
temporal variations. A method for such a repre- 
sentation was used by Weickmann [1957a]. An 
example for this method is given in Figure 1. Of 
the two columns of the ordinate the first contains 
typical forms that require only shght ice super- 
saturation for their growth. The second column, 
however, comprises forms whose growth occurs 
at or close to water saturation. The diagram 
shows two periods, where the precipitation clouds 
reached up into upper layers of the troposphere. 
A cloud layer with water saturation existed in the 
—15 to —20° C temperature range in agreement 
with the aerological cross section. During the 
forenoon such a layer existed also between —10 
and —15° C discharging malformed plane crys- 
tals. Also the disappearance of the upper pre- 
cipitation clouds during the evening hours can be 
seen, 
Quantitative analysis—If the rate of fall and 
the rate of growth for each crystal type are also 
known, these facts in connection with the size of 
the grown erystal type allow calculation of the 
thickness of layers through which the particle fell 
and in which these conditions were met. With this 
supplementary statement the qualitative analysis 
is extended to a quantitative analysis. From the 
arrangement of these originating zones a cross 
section of the isotherms and isohumes can be 
constructed. 
For both quantities, the rate of fall and the 
rate of growth, Nakaya’s values were used. The 
rate of fall proves to be nearly constant for all 
dimensions of plane and spatial dendrites as well 
as of powder snow. For erystals with droplets and 
even more for needles and graupels the rate of 
fall increases with their size. The degree to which 
the rate of fall depends upon the density of air, is 
not known and cannot be considered. The great- 
est influence, however, should be exerted by the 
vertical air transport. But the appearance of up- 
ward currents is limited to certain weather situa- 
tions with a character of instability. For the com- 
putations here average values of the rate of fall 
