DISCUSSION 
found a profound difference between ocean and 
continent. Figure 6 gives the essence of these ob- 
servations. Whereas the difference in concentra- 
tion is comparatively small for the giant par- 
ticles larger than 1p radius, there is an increasing 
lack of nuclei over the ocean when approaching 
0.1, radius. Unfortunately, there are no data 
below 0.1 for the ocean, but there is some indi- 
cation for a secondary increase as indicated by 
the part with a question mark. 
Now, the nuclei between 1 and O.1p are the 
most important ones for cloud-droplet forma- 
tion. In Figure 7 we converted these size dis- 
tributions into supersaturation spectra and com- 
pared them with the observed supersaturation 
spectra of Twomey. It can be seen that the 
agreement is good considering the fact that the 
two sets of data were obtained in completely 
different geographical locations. The fact that 
CONTINENT 
PARTICLES / Cm> —» 
0.01 O.l 1.0 
—-+ RADIUS OF NUCLEUS 
Fic. 6—Size distribution of aerosols (1) over 
land, and (2) over the ocean; the curves give, in 
contrast to earlier presentation, the total number 
of particles larger than the indicated value of the 
radius (cumulative figures) 
Op 
PARTICLES / Cm3 
0.1% 
SUPERSATURATION 
— 
1.0% 10 % 
Fic. 7—Supersaturation spectra, (1) calculated 
from Curve (1) in Fig. 1; (2) calculated from 
Curve (2) in Fig. 2; measurements by Twomey 
over Australia: (3) drought conditions; (4) conti- 
nental air masses; (5) maritime air masses; the 
curves give the total number of particles active 
above the indicated supersaturation 
our maritime curve is still lower than the cor- 
responding values of Twomey may indicate some 
continental aerosol residues in the Australian 
maritime air where the data were obtained. Two- 
mey’s data were taken from a manuscript sub- 
mitted to the Geofisica Pura et Applicata, which 
Dr. Squires made available to me. 
(2) The role of sulfate as a substance of con- 
densation nuclei in areas which are normally 
considered completely unpolluted, and a pos- 
sible difference between the southern and north- 
ern hemispheres. We found that about 50% of 
the atmospheric sulfur in the northern hemi- 
sphere is due to industrial activities. Since we 
know that sulfate is an important constituent 
of the condensation nuclei, it may be that during 
the industrial development within the last 100 
