148 
CHOJI MAGONO 
_ 
2000 | 
| 
1500 © 
1000 | 
7a 
= 
fal 
a 
=) 
=] 
= 
=] 
+ 500+ 
| 
5 -10 eG | 
TEMPERATURE 
60 80 100 % 
REL.HUM. (ICE SAT) ~ 
Fig. 8—Growth of plane dendritic snow crystals observed at point 1000 
and point 500, 21h 00m—21h 10m, Jan. 28, 1959; shading in column shows 
the temperature region of snow crystal growth for the crystal type indi- 
cated 
Nd 
i=) 
3 
0 i} 2 3 4 5 
DIAMETER OF SNOW CRYSTAL IN MM 
Fig. 9—Size distribution of plane dendritic snow 
crystals observed at three observation points, 
21h 30m-21h 50m, Jan. 28, 1959 
highly supersaturated humidity which requires 
the existence of cloud droplets in air in the nat- 
ural case. But if the air contains cloud droplets, 
the snow crystals will collect and cannot be 
called ‘beautiful crystals.’ It therefore appears 
that beautiful plane dendritic snow crystals grow 
in air of humidity lower than that assumed from 
laboratory experiments, in other words, they 
grow at the humidity very near to ice saturation. 
In this case, the existence of cloud droplets is not 
necessary. 
Time Section C: It was characteristic here 
that the lapse rate of the air temperature was 
very small and the atmosphere was saturated 
from near surface to altitude 6000 m as shown 
in Figure 4. The air layer with temperatures 
ranging from —5°C to —8°C was very thick. 
This condition is suitable for the growth of thin 
