CLOUD DISTRIBUTIONS OVER TROPICAL OCEANS 
wave trough, while it is pronounced in the 
convection zone of the disturbance. A more de- 
tailed study of organization in the region of 
the easterly wave trough is shown in Figure 5 
where we have mapped schematically the cloud 
lines ahead and to the rear of the disturbance. 
The spacing of the cloud lines is to scale, but 
not individual clouds. The large blobs located 
about 100 km apart in the convection zone are 
actually large groups of huge buildups which 
were regularly spaced at these intervals along 
the parallel cloud lines, giving the impression of 
a normal mode of organization. Beginning at 
about halfway between Honolulu and Kwajalein, 
we measured the spacing of these cloud lines; it 
began at about 4 km between rows, comparable 
to the depth of the moist layer. As the wave 
trough was approached, the row spacing became 
wider until it reached about 25 km just east 
of the wave trough and about 30 km just west 
of it. It appeared that the spacing was being 
widened by superposition of a larger-scale or- 
ganization upon the smaller (4 km) scale and 
that some of the cloud rows were being en- 
hanced while those between were being sup- 
pressed. 
Finally, Figure 6 shows the high-level chart, 
the D-values and average winds for the 250- 
150-mb layer which prevailed at the time of Leg 
1. The important point to note is that the 
easterly wave trough lies just to the west of the 
upper anticyclone and to the east of an upper 
cyclone, which was stationary. While the ob- 
server and aircraft spent the night at Kwajalein 
the wave trough passed by and moved under- 
neath this upper cold low. On the next day’s 
flight it should have been encountered about 
200 miles out of Kwajalein, but only faint 
remnants of the previously vigorous wave were 
detected. There was hardly any trace of dis- 
turbance left along the path of the aircraft 
except five or six very distant Cumulonimbi 
on the southern horizon, which may have been 
associated with the equatorial trough. The syn- 
optic study showed the air rounding the south- 
ern bend of the upper trough was likely to gain 
cyclonic relative and absolute vorticity. Upper 
level convergence and consequent sinking pre- 
sumably destroyed the easterly wave and Figure 
7 shows its total demise in the streamline field 
in the Marshall area. The cloud motion picture 
films showed its death far more dramatically, 
however, than any of our words or diagrams. 
or 
or 
Figure 8 shows three selected frames from the 
motion picture film; a and b were made to the 
west and east, respectively, of the wave trough 
on its first crossing on Leg 1. The cloud line 
seen in Figure Sb appears as the first one to 
the west of the trough line in Figure 5, and the 
large cloud build-up, in the distance reached 
50,000 ft. Figure Se shows the ‘convection zone’ 
of the trough on its second crossing by the air- 
craft on Leg 2 (after the overnight stop at 
Kwajalein). Note the complete disappearance 
of the disturbance, except for the very distant 
build-ups far to the south. 
In conclusion, this work suggests that micro- 
physical studies of tropical clouds and_ pre- 
cipitation would be severely restricted if studied 
out of context with the synoptic scale flow pat- 
terns. If we wish eventually to predict, under- 
stand, or in any sense modify tropical rain, the 
interaction between large-scale flows, convection 
dynamics, and droplet formation and growth 
must be studied. 
Note—At the Conference this paper was con- 
cluded by showing the portion of the cloud films 
from which the figures shown here were con- 
structed. These films were made from military 
aircraft flying at 8000-ft altitude, and were taken 
in kodachrome at one frame per second. These 
films are on file at the Woods Hole Oceano- 
graphic Institution and at the Department of 
Meteorology, University of Chicago. The meth- 
ods of photography and reduction are described 
in detail in the Report [Riehl and others, 1959] 
of which this paper is a partial condensation. 
Acknowledgments—The writers wish to ac- 
knowledge the essential contribution made to 
this study by their colleagues at the University 
of Chicago, Herbert Riehl and William Gray, 
who carried out the synoptic analysis described 
herein. The work when completed is to be pub- 
lished under joint authorship with them. 
This study was supported by the National 
Hurricane Project of the U. 8S. Weather Bureau 
and by the Office of Naval Research. Its execu- 
tion was made possible through the kind co- 
operation of the Military Air Transport Service 
(Pacific Command) whose staff and crews went 
far beyond the call of duty to provide assistance. 
REFERENCES 
Bunker, A. F., B. Haurwirz, J. S. Mauxus, anp 
H. Srommen, Vertical distribution of tempera- 
ture and humidity over the Caribbean Sea, 
Pap. Phys. Ocean. and Met., Mass. Inst. of 
