CLOUD DISTRIBUTIONS OVER TROPICAL OCEANS 47 
cloud lines wherever they occurred and their 
spacing on numerous occasions. 
As a corollary to the above conclusions it 
was found possible to devise a code for the state 
of the tropical sky, with relatively few numbers, 
so that the code number chosen provides sig- 
nificant information about the synoptic pattern 
and physieal processes at work. It consists of 
17 basic sky types, ten for trade-wind skies 
and seven for disturbed skies. The code itself 
and an illustration of each number (a single 
frame chosen from our films) is contained in the 
Appendix. The code was used by us to char- 
acterize long strips of prints which were made 
from the movies at 15-min intervals; the ap- 
propriate code numbers are then plotted along 
maps of the fight path and used as underlays for 
the synoptic charts, as will be seen in the figures. 
A person can obtain a good visual image of the 
cloud forms during any portion of any flight 
by looking at the code number and referring 
to the sample print thereof, a result which is, in 
itself, of some interest. Conversely it may be 
hazarded that a meteorologist well acquainted 
with the three-dimensional synoptic picture 
could, with practice, enter in anticipation the 
code numbers along a projected flight path with 
little error. 
We shall now illustrate our techniques, ap- 
proaches, and some of our results by showing 
first the analysis and lastly the movies them- 
selves of a small portion of Flight I. Figure 1 
shows the path and times of this flight, which 
passed through an undisturbed trade regime 
from Hawai to Johnston Island, into and 
through a moderate easterly wave just east of 
Kwajalein (in the Marshalls) where the first 
overnight stop was made. The wave passed 
Kwajalein during the night and thus was en- 
countered again by the aircraft the following 
morning. After this the flight proceeded on to 
Guam and Manila, where on this last leg it 
passed through the typhoon Wendy. We shall 
be concerned here, however, only with the two 
passages through the easterly wave. The re- 
mainder of Flight I is analyzed in detail in the 
Report [Riehl and others, 1959]. Figure 2 
shows the flight path of the first lee with the 
cloud code numbers entered along it used as an 
underlay for the low-level streamline chart. All 
code numbers entered refer to ‘trade-wind skies’ 
(code numbers 1-4) or ‘trade-wind disturbance’ 
(code numbers 6-9), the latter in this case as- 
sociated with the moderate-strength Riehl-type 
easterly wave, whose trough line was centered be- 
tween Majuro and Kwajalein, and which was 
moving westward at approximately ten knots, or 
more slowly than the trade flow. 
We would thus expect the convection and 
precipitation zone to be located east of the 
troughline; the pictures confirmed this in a 
striking manner. Note the code numbers 8 and 
9 (Cumulus congestus, high Cumulus tops and 
showers; the only difference between the two is 
that 9 contains upper clouds, broken to overcast) 
appearing up to the wave trough, and then cut- 
ting off sharply ahead, going over to ordinary or 
even suppressed trade-wind skies. The quanti- 
tative measurements from the films bring out 
even more clearly the effects of the disturbance 
upon the cloud structure. Figure 3 shows the 
cloud cross section of this leg constructed from 
the film analysis, superimposed upon a relative 
humidity cross section composited quite inde- 
pendently from the radiosondes and synoptie 
data. 
The horizontal dimensions of the sketched 
Cumuli (as well as the hatched under curve be- 
low) gives the cloud amount, while the dashed 
cloud outline indicates the maximum height of 
tops; the average top height is shown by the 
darker outlines. The effects of the inversion 
domination near flight outset, its relief at about 
Johnston Island and gradual approach to the 
wave convergence zone are pronounced. Note 
the upper regions of high humidity in connection 
with the subtropical jet over Hawaii and with 
the level of maximum wave amplitude (15,000- 
20,000 ft) in the Marshalls area and the as- 
sociation of these with middle and upper cloud- 
iness. It is worthwhile to remark here that 
Flights IT and TI crossed this area without a 
wave disturbance and only trade-wind or sup- 
pressed skies were photographed. 
Figure 4 shows arrows denoting the orienta- 
tion of the cloud lines, and vertical marks the 
number of which is proportional to the intensity 
of this organization into rows. We see that the 
cloud lines are parallel to the low-level stream- 
lines, within the accuracy of our ability to draw 
these (except perhaps just west of the wave 
trough where the cloud lines were backed al- 
most north-south and no wind information ex- 
isted to test whether or not the flow was so 
oriented). We also see that the organization 
into rows is weak or absent in the inversion- 
dominated portions of the flight; namely, just 
out of Hawai and just west (ahead) of the 
