DISCUSSION 
Scuarrer, V. J., The concentration of ice nuclei 
passing the summit of Mt. Washington, Bul. 
Amer. Met. Soc., 35, 310-814, 1954. 
Sounace, G., Contribution des fumées industrielles 
a Venrichissement de l’atmosphére en noyaux 
245 
glacogénes, Bul. Obs. dw Puy de Dome, pp. 121- 
124, 1958. 
Warner, J., An instrument for the measurement of 
freezing nucleus concentration, Bul. Obs. du 
Puy de Dome, pp. 33-46, 1957. 
Discussion 
Mr. D. Blanchard—I think I would be one of 
the last to discourage any work related with 
phenomena of the air-ocean interface, but I 
think a word of caution might be in order. One 
produces aerosols by bubbling or spraying. Any 
way in which one produces aerosol from sea wa- 
ter or distilled water means this aerosol will 
come from the surface. This means any surface 
contamination on this water will end up in the 
aerosol, and if one has any surface active con- 
tamination, this may be what you are actually 
measuring. I think these experiments certainly 
should be carried out using very clean condi- 
tions, perhaps using artificial water. 
Mr. D. B. Kline—We have tried distilled 
water. Carefully distilled water did not give a 
response. Tap water, however, did. We have 
tried sodium chloride, magnesium chloride, and 
calcium sulphate solutions and we consistently 
got a response. 
Dr. H.-W. Georgii—In January 1957 we had 
very marked peaks at about the same dates at 
which Dr. Bowen had them. At that time, I 
did not yet know of Bowen’s work. We believe, 
as does Mr. Kline, that they are connected with 
the large-scale flow pattern of the atmosphere, 
and perhaps the change from zonal to meridional 
circulation that we had at this time in 1957. 
Dr. Tor Bergeron—I thought our freezing nu- 
clei measurements in January 1959 were of very 
little value; but I shall now be very glad to have 
them compared with yours. 
Mr. Kline—I am very glad to establish this 
contact and I am very interested in the data. 
Dr. Choji Magono—A group in Japan under 
Dr. Isono at Tokyo University made observa- 
tions like you, using different methods. They 
found that peaks of concentration of freezing nu- 
clei agreed very well with volcanic eruptions in 
Japan. This was derived using the trajectory 
method. 
Mr. Kline—I was interested in the report that 
the freezing nuclei concentration was not only 
correlated with voleanic eruptions, but could also 
be traced back to the latest dust storm in 
northern China (see reference to Jsono and 
others im my paper). 
Mr. Jerome Namias—In the synoptic situation 
for maritime flow in the Washington, D. C., 
area, there is usually a very strong vertical wind 
shear, so that fresh maritime air is seldom ob- 
served up to high elevations. It is a warm-front 
condition in which if the air flow is fresh from 
the ocean in the lowest levels, it changes to a 
continental flow aloft. Frequently the precipita- 
tion mechanisms develop in the higher layer, 
so that this type of stratification should be con- 
sidered in regard to these observations. 
Mr. C. BE, Anderson—I wonder whether or not 
measuring ice nuclei at the surface is of any real 
value in getting an estimate of what the ice nu- 
clei activity is likely to be aloft. Since there is 
not only a question of separation of trajectories 
with height, but also the influence of contamina- 
tion at the surface. 
Mr. Kline—All we can do to attempt to get 
around the problem is set up our network to in- 
clude high altitude stations. 
Dr. C. L. Hosler—What are the short-period 
variations in these ice-nuclei counts? The data 
you presented is the result, I presume, of a 
number of counts. How many and over what 
period of time? What would happen if you 
waited an hour longer, would this result in a 
greater variation from day to day? 
Mr. Kline—It takes about 60 to 90 min to run 
through a spectrum such as is presented in Fig- 
ure 3. Durmg that period we normally have 
variations only within roughly a factor of two 
or three. Reproducibility is usually good; but 
we do encounter periods where there is con- 
siderable variation. 
Dr. H.-W. Georgii (communicated)—In the 
course of our own measurements off the Irish 
west coast we also found a relatively high num- 
ber of freezing nuclei active above —20°C. The 
absolute number of freezing nuclei within this 
temperature range was even higher than on the 
Zugspitze and equally as high as in Frankfurt. 
However, at lower temperatures (between —20 
