Structure of Snowfall Revealed by Geographic 
Distribution of Snow Crystals 
Cuost Macono 
Hokkaido University, Sapporo, Japan 
Abstract—The Cloud Physics Group of Japan made observations of snow crystal 
forms by various methods at five points which were distributed vertically from eleva- 
tions of 100 m to 1000 m at Mt. Teine, Hokkaido, through the period January 26-31, 
1959. Aspirated psychrometers and rawinsondes were mainly used to measure the air 
temperature and humidity. 
The results are summarized as follows: (1) Nakaya’s T,-s diagram represents fairly 
well the growth of natural snow crystals. The crystal forms observed at the Earth’s sur- 
face are mainly affected by the temperature and humidity of air layers at altitudes 
lower than 2000 m. (2) It seems that sometimes dendritic snow crystals grow at a hu- 
midity very near to ice saturation, or at least at a lower humidity than water saturation. 
(3) The necessary conditions for the formation of large snowflakes are the existence of 
a thick moist atmospheric layer and of air temperature higher than —10°C. 
Introduction—The relation between the snow- 
crystal forms and the meteorological conditions 
was studied by Nakaya in laboratory experi- 
ments, and his theory was proven by Gold and 
Power [1954], Murai [1956], and Kuettner and 
coworkers [1958] using aerological sonde data 
obtained during snowfall. As for the growth of 
natural snow crystals, however, there are no 
available observational data. In order to be able 
to observe the rate of the growth, observations 
were made at several points distributed verti- 
cally. 
The Cloud Physics Group of Japan made the 
observation of natural snow crystals by various 
methods at five observation points distributed 
vertically at Mt. Teine in January 1959 and 
measured the form and size of snow crystals of 
almost all types. 
Methods employed—As one sees in Figure 1, 
Mt. Teine is located about eight miles north- 
west of Sapporo where rawinsonde soundings 
were carried out by the Sapporo Meteorological 
Observatory at O09h00m, 15h00m, and 21h00m 
each day during the period of the observations. 
Since the predominant wind direction during the 
period was from the northwest, the observing 
points are located on the windward side, there- 
fore the atmospheric conditions measured by 
the aerological sounding may differ somewhat 
from those above the mountain except for the 
case of large uniform snowfall. 
The horizontal distribution and vertical dis- 
tribution are shown in Figures 2 and 3. The ob- 
14 
servation points at altitudes 1023 m, 800 m, 560 
m, 300 m and 100 m are called Point 1000, Point 
800, Point 500, and so on, respectively, in this 
paper. The upper three points are close together, 
but the lower two points are somewhat far from 
the upper points; accordingly, snow crystals ob- 
served at the lower two points were sometimes 
not recognized as belonging to the same cloud 
system. Frequently no snowfall was observed at 
the lower points even when moderate snow 
showers were observed at the upper points. This 
discrepancy is considered to be due to orographie 
effects. 
The observers and their work during the ob- 
servation are listed in Table 1. 
The work of the observer at Hokkaido Uni- 
versity was to identify the clouds over Mt. Teine 
from outside of the observing area. This work 
was very useful, because the observers located at 
the mountain often could not observe the clouds 
by which they were surrounded. Among the 
methods employed in observing snow crystals, 
the securing of replicas and microscopic photo- 
graphs were most useful. As for the measure- 
ment of humidity, Assmann’s aspirated psy- 
chrometer was most reliable. 
The observations at the five points were car- 
ried out simultaneously, every ten minutes dur- 
ing three hours after the rawimsonde sounding 
times (09h00m, 15h00m, 21h00m) from Janu- 
ary 26-31, 1959. 
Results—The time cross section obtained us- 
ing aerological sounding only is shown in Figure 
