HORIZONTAL DISTRIBUTION OF SNOW CRYSTALS 
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PACIFIC 
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Fre. 1—Map of Hokkaido 
Results of observation—In the 40 days of the  drites were observed widely and continuously 
period of observation, there were six days when 
snowfall was not observed at all observation 
points. On all other days, snowfall was observed 
at one or more of the stations. It can be said, 
therefore, that snowfall occurred in the observa- 
tion area almost every day in the period of ob- 
servation. Snowfall was observed at all stations 
on 4 days; namely, January 20 and 30, and Feb- 
ruary 10 and 16. The horizontal distribution of 
snow crystals and its time sequence observed in 
these four days will be described in the following. 
On January 20, the snowfall was associated 
with the continental monsoon system. Sea-level 
and 700-mb charts at 09h 00m are shown in Fig- 
ure 3. As seen in Fig. 3a, the snowfall area was 
the northern part of the Japan Sea Coast of Ja- 
pan. The amount of precipitation on this day was 
1.7 mm at Sapporo and 3.4mm at Iwamizawa. 
The horizontal distribution of snow crystals at 
09h 30m, 10h 30m, 11h 30m, and 12h 30m is 
shown in Figure 4. In these figures, the observed 
shapes of snow crystals are indicated by the 
graphic symbols of the practical classification. 
The graphic symbol shown at the observation 
point indicates the shape of snow crystal observed 
most frequently; the graphic symbols in paren- 
theses indicate those observed less frequently. In 
these figures, no graphic symbol is shown at some 
observation points. This does not mean, however, 
that snowfall did not occur at that place, but that 
the observation of snow crystals was not carried 
out. The open circle indicates that snowfall had 
stopped at the time of observation. As seen in 
these figures, the stellar crystals and spatial den- 
during the period of observation. Plates were ob- 
served in the southeast region indicated by P. 
At 09h 30m, needles were observed in the east 
region indicated by N. 
The sounding curve at O9h 00m is plotted 
in Figure 5. In the left part of this figure, the 
full line indicates the relative humidity with re- 
spect to water, and the dotted line indicates that 
with respect to ice. In the right part, the broken 
lines indicate the wet adiabatic lines. The wind 
aloft at 0.5 km intervals is shown at the left, 
where the long wing indicates 10 m/sec and the 
short one indicates 5 m/sec. These notations are 
also used in the figures that follow. From the 
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10 KM 4 
Fic. 2—Topographical map of the observational 
area 
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