144 
CHOJI MAGONO 
Tasie 1—The data-gathering organizalion 
| 
Observation points Altitude Terms of observation Observer 
= = 
Point 1000 1023 Chief | Choji Magono 
Daisuke Kuroiwa 
Point 1000 1023 Humidity Kazuhiko Itagaki 
Humidity, temperature _ Shoichi Koenuma 
Close-up photographs Katsuhiro Kikuchi 
Microscopic photographs 
Replicas of snow crystals / Tsutomu Takahashi 
: \Tsutomu Nakamura 
Point 800 800 Humidity, temperature {Tsutomu Takahashi 
(Tsutomu Nakamura 
Point 500 560 Replica Se eae : 
Shadowing photographs { Soup stave 
Close-up photographs | : 
Microscopic photographs | Jiro Muse 
Humidity, temperature Tadashi Kimura 
Point 300 300 Humidity, temperature {Keitaro Orikasa 
Replicas \ Ken-ichi Sakurai 
Point 100 100 Humidity 
Close-up and microscopic photo- | Teisaku Kobayashi 
graphs 
Replicas Toshiichi Okita 
Shadowing photographs Goro Walahamal 
Humidity, temperature 
Hokkaido University 30 Replicas \ Muasahilco Sivenide 
Cloud photograph{ 
Sapporo Meteorological 30 Rawinsonde Sapporo Meteorological 
Observatory Observatory 
at each three-hour interval is shown at the upper 
part of the figure schematically. The first type 
shown on each of the top lines means the type of 
snow crystal which fell most frequently. The re- 
gion of humidity higher than ice saturation is 
shown by shaded area. Cloud bases are shown 
only when ascertained. From the figure it may be 
seen that moist atmosphere layers (hatched 
areas), exist near or above Point 1000 always 
when snowfall is observed at Point 1000. The 
only exception is on the night of 28th. This is im- 
portant; it will therefore be discussed later. 
According to Nakaya’s 7,-s diagram, a tem- 
perature of —15°C is suitable for dendritic snow 
crystals to grow, while at a temperature of —5°C 
snow crystals grow to needle form. From an in- 
spection of Figure 6, note that from the 26th to 
28th when the —15°C isotherm existed near or 
above the top of the mountain, dendritic snow 
erystals were predominant, and on the 30th when 
the —15°C isotherm had descended to this alti- 
tude, only thin hollow columns or needles were 
observed. One may understand that Nakaya’s 
diagram agrees very well with the type of natu- 
ral snow crystals. This fact leads to the con- 
clusion that the type of snow crystals is con- 
siderably influenced by the temperature of the 
air layer lower than 2000 m. It is well known that 
in the 7',-s diagram the region of column and 
plate type is distributed symmetrically around 
the dendritic region: that is about —15°C. How- 
ever considering the time cross section it is possi- 
ble that the snow crystal type falling naturally is 
mainly affected by the warmer region of two tem- 
perature regions of crystal formation. This is con- 
sidered to result from the fact that at the higher 
level the vapor density is small as is the air 
density. The absolute vapor content is small even 
if the air of the upper level is saturated because 
the air is colder than that at the lower level. Ac- 
