i) 
i=) 
rs 
Relative Humidity (%) 
% 3g yee 8 BB 
4 
Radius (cm) 
° 600 1200 1800 2400 3000 3600 
Time (seconds) 
Fic. 12—Variation of relative humidity and 
growth curves for various drop-size groups, Cumu- 
lonimbus Case 
The change in liquid content from 3 Xx 1074 to 
0.3 grams per m* occurs in three minutes in this 
case, compared to ten minutes in the Stratus cases. 
By ten minutes after saturation the liquid con- 
tent has reached 1.6 grams per m*, and at 3400 
see it reached a peak value of 6.8 grams per m°. 
The subsequent decrease is due to the expansion 
of the ascending air parcel, which begins to over- 
balance the condensation at that time. As in the 
Stratus cases, the 0.1 micron group is responsible 
for most of the liquid content. 
The decrease in visual range in the Cumulonim- 
bus is likewise more rapid, and the visual range 
reaches lower values, with a minimum of 7.2 m 
at 3300 sec. 
Except insofar as it might affect the condensa- 
tion process, the development of drop growth by 
collision and coalescence would not affect the 
liquid content if we assume that the parcel re- 
NEIBURGER AND CHIEN 
ceives as many of the larger drops from above as 
fall out of it. The visual range, however, would be 
influenced considerably, for the removal of 
smaller drops would reduce the scattering area 
much more than the growth of the larger drops 
would increase it. 
The Trade-Wind Cumulus Case—In the Trade- 
Wind Cumulus Case the large vertical velocities 
assumed for the lower portion of the cloud (see 
Fig. 3) resulted in saturation being reached ear- 
her than in the Cumulonimbus Case; namely, at 
816 sec; and a higher maximum supersaturation, 
0.24 per cent at 835 sec, being attained (Fig. 16). 
The second maximum in relative humidity, which 
occurs near the level of maximum vertical ve- 
locity, has no significance in terms of activating 
new nuclei. 
Because of the higher maximum supersatura- 
tion, not only is the additional nucleus group at 
0.056 micron activated (as in the Stratus Case B), 
but so is the 0.032 micron group. This, together 
with the larger number of giant nuclei in the as- 
sumed initial distribution, results in larger num- 
E “RSs 
Ea | N Sige 11300 sec 
‘i pas aS TS Sy, 1=|BOO sec 
ae = a Seta ete2400'sec 
——" =I 
E \ } Valine | 
E 120 \te1150 \ | \tsi200} 11 p-1= 3600sec 
JE sec sec | 
i \ \ eal 
i 
Oe ee \ ee 
TM TT a TTT 
Number Greater than Given Radius per Cubic Centimeter 
10? — —}— 
= 
E 
OE =e 
=: 
Ir 
le 
= } 
10 
al 
——— 1 
oh 10° 10 10° 10? 10' cm 
ool ol 10 10 100 1000 microns 
Drop Radius 
Fig. 13—Cumulative drop-size distributions after 
various elapsed times, Cumulonimbus Case 
