128 DISCUSSION 
REFERENCES 
Gop, L. W., anp B. A. Powrr, Dependence of the 
forms of natural snow crystals on meteorolgical 
conditions, J. Met., 11, pp. 35-42, 1954. 
Murat, G., On the relation between natural snow 
crystal forms and the upper-air conditions, Low 
Temp. Science, ser. A, 15, 13-32, 1956, in Japan- 
ese, with English resume. 
Kuertner, J, P., anp R. J. Boucuer, A study of pre- 
cipitation systems by means of snow crystals, 
synoptic and radar analysis, Mount Washing- 
ton Observatory, 1958. 
Naxaya, U., Snow crystals, natural and artificial, 
Harvard University Press, 510 pp., 1954. 
Wercxmann, H. K., Physics of precipitation, Me- 
teorological Monographs, 3, no. 19, 226-255, 
1957. 
Naxaya, U., The formation of ice crystals, Com- 
pendium of Meteorology, Amer. Met. Soc., pp. 
209-220, 1951. 
Discussion 
Dr. Helmut Weickmann—How reliable are 
your humidity measurements? 
Dr. Nakaya—These measurements are made 
with a hygrometer developed by Dr. Kobayashi 
of the Central Meteorological Institute in Tokyo. 
He has a ten-year experience with such measure- 
ments and succeeded in developing an instrument 
which is superior to other hygrometers. 
Dr. B. J. Mason—If there is an isolated cloud 
with nothing above or below, any crystals which 
are collected come from just this layer. Then one 
can deduce its temperature and perhaps the hu- 
midity. I am doubtful of this deduction, if there 
Fra. 19—A three-layer cloud 
is a deep cloud system where there is a large tem- 
perature range. In England, I generally observe 
in 90% of the cases a mixture of crystals of all 
sorts which come from a deep cloud layer system, 
and everything is mixed up and it is impossible 
to make any useful observations. I should like to 
ask Dr. Nakaya if he agrees with this, and ask 
him if he belleves that one can only make this 
kind of an analysis when in fact, you have rather 
well defined thin cloud layers from which the 
crystals fall? 
Dr. Nakaya—That I expected. This is a very 
interesting and important problem. If the clouds 
had three layers (Fig. 19) A, B and C, and snow 
crystals come down in the vertical, we must ex- 
pect on the ground three types of snow; C, C plus 
B, C plus B plus A. If A is plate, B is dendritic, 
and C is needle, we can expect needle, dendrite 
with needles, plate with dendritic extensions with 
needles attached; something like that. But it was 
not thus. Sometimes we observed the combined 
type, but usually simple type of erystal corre- 
sponding to each layer of the clouds was observed. 
In this year’s observations we found that when 
the upper-air condition is layered A, B and C, the 
upper type A or the middle type B was observed 
on the ground. They appear to have escaped 
layer B or C. This is against our simple assump- 
tion of vertical fall, and we must develop the 
theory to explain this phenomenon. This is a fu- 
ture problem, but anyhow when we observe three 
or four kinds of crystal types on the ground we 
see that three or four corresponding layers are 
in the upper levels of atmosphere. The only ex- 
planation at present is that the atmosphere has a 
cellular structure or is in the turbulent condition 
and is not made up of horizontal strata. In this 
case a certain type of erystal can come down to 
the ground without passing through the stratum 
beneath. So this is a problem of the microstruc- 
ture of the atmosphere. 
Dr. Weickmann—(answering Dr. Mason) In 
fact, your observations of various kinds of snow 
crystals were interesting because it indicates that 
you have a deep and vigorous cloud system. If 
you observe only one type of crystal, the cloud 
system underneath the generating layer is not 
vigorous enough to produce its own crystals, it is 
just able to nourish the crystals which fall 
through, but in other more vigorous cloud sys- 
tems you may get the crystals initiated in several 
levels, and then you observe several types; and 
this seems to be the case in the systems you ob- 
served. 
Mr. L. Aldaz—During the winter of 1956- 
