GROWTH OF CLOUD DROPS BY CONDENSATION 
203 
10° 
Lit 
3, 
® 
Liquid Content (Grams m°>) 
& 
Visual Range (Meters) 
0056+} 
010 
Visual Ronge 0" 
2000 
3000 
5000 
Time (Seconds) 
Fic. 11—Variation of liquid content and visual range (for light of wave- 
lengths 4000 and 7000 A), Stratus Case B; thin lines show liquid content in 
various drop-size groups 
These figures may be compared with the data of 
Bowen, Smith, and Styles and Campbell cited by 
Mason [1957] for non-freezing showers in south- 
eastern Australia. Four of the six cases with radar 
data had echoes spreading downwards from levels 
between 7000 and 10,000 ft, and all of the six 
cases for which radar data was not available had 
clouds extending above 8500 ft. Mordy and Eber 
[1954] reported that rain occurred in the cases 
they studied of the orographic rainfall in the 
Hawaiian Islands whenever the cloud extended 
more than 5000 ft above the cloud base of 2000 
ft. While the clouds in the cases cited were differ- 
ent than the thunderstorm Cumulonimbus for 
which the assumed vertical velocity distribution 
is typical, the correspondence of the height of 
radar echo or the thickness of precipitating clouds 
with that required in the model for development 
of drops large enough to initiate the warm cloud 
precipitation process suggests that the general 
magnitudes involved in the computation have 
some relationship to natural processes. 
With the more rapid cooling, the cloud develop- 
ment occurs more rapidly in the Cumulonimbus 
case than in the Stratus cases. At 1200 see (Fig. 
14) the second mode in the differential frequency 
curves is just beginning, at about 0.5 micron; less 
than two minutes later it is well developed at 
5.4 microns, with a conspicuous gap at about four 
microns. The mode moves rapidly to larger sizes 
exceeding ten microns after five more minutes and 
reaching 20 microns by 3600 sec. The rapid de- 
velopment of the cloud is shown likewise by the 
liquid content and visual range curves (Fig. 15). 
